Macromol doi: 10.3390/macromol4030026

Authors: Robe D. Terfa Priyanshi N. Patel Hwidong D. Kim Matthew D. Gacura Gary Vanderlaan Longyan Chen Xiaoxu Ji Davide Piovesan

The utility of brewery spent grain (BSG), a byproduct of the beer production process, for the synthesis of polyhydroxyalkanoates (PHAs), is a significant advancement towards sustainable and cost−effective biopolymer production. This paper reviews the upcycling potential of BSG as a substrate for PHA production, utilizing various biotechnological approaches to convert this abundant waste material into high−value biodegradable polymers. Through a comprehensive review of recent studies, we highlight the biochemical composition of BSG and its suitability for microbial fermentation processes. This research delves into different methodologies for PHA production from BSG, including the use of mixed microbial cultures (MMCs) for the synthesis of volatile fatty acids (VFAs), a critical precursor in PHA production, and solid−state fermentation (SSF) techniques. We also examine the optimization of process parameters such as pH, temperature, and microbial concentration through the application of the Doehlert design, revealing the intricate relationships between these factors and their impact on VFA profiles and PHA yields. Additionally, this paper discusses challenges and future perspectives for enhancing the efficiency and economic viability of PHA production from BSG. By harnessing the untapped potential of BSG, this research contributes to the development of a circular economy model, emphasizing waste valorization and the creation of sustainable alternatives to conventional plastics.

Macromol doi: 10.3390/macromol4020025

Authors: Ricardo Troncoso Ana Torrado Nelson Pérez-Guerra Clara A. Tovar

The effects of using a hard (artisanal) margarine (which has a higher lipidic and lower aqueous contents) and using a soft (commercial) margarine (which has a lower lipidic and higher aqueous contents), along with a casein hydrolysate, on the rheological properties of different biscuit short doughs were examined. The characteristic parameters in the linear viscoelastic range (LVER) were analysed by stress sweep at 6.3 rad/s and 25 °C. The two margarines showed similar values of strain amplitude (γmax), but the hard margarine exhibited a significantly higher firmness in the LVER, as expected. An analogous result was found for the biscuit doughs made with hard margarine and soft margarine. The addition of a casein hydrolysate (CH) to both biscuit doughs produced an increase in the loss factor, indicating a loss of the solid-like character in the dough networks. Nevertheless, a different trend in the consistency of the dough, which depended on the type of margarine, was found. While, after adding CH, the dough made with soft margarine showed a significant reduction in rigidity, the dough with hard margarine exhibited an increased firmness upon CH addition. Yield stress tests showed that CH facilitates the transition from elastic to plastic deformation at the yield point more intensely in the dough with soft margarine.

Macromol doi: 10.3390/macromol4020024

Authors: Onome Obodo-Ovie Mohammad Alyassin Alan M. Smith Gordon A. Morris

Green peppers are massively produced all over the world; however, substantial quantities of peppers are wasted. Functional polysaccharides can be produced from pepper waste. A conventional acid extraction method was used to obtain pectin-like materials from green bell pepper (GBP). A 23 experimental design (two-level factorials with three factors: temperature, pH, and time) was used to study the relationship between the extraction conditions and the measured physicochemical properties. The extracted polysaccharides were further analysed regarding their physicochemical and functional properties. The yields were in the range of (11.6–20.7%) and the highest yield value was extracted at pH 1. The polysaccharides were classified as “pectin-like”, as the galacturonic acid content was lower than 65%. Glucose and galactose were the major neutral sugars, and their relative amounts were dependent on the extraction conditions. The degree of esterification (DE) of the pectin-like extracts was greater than 50% and they were therefore classified as high methoxyl regardless of the extraction conditions. Also, important levels of phenolic materials (32.3–52.9 mg GAE/g) and proteins (1.5–5.4%) were present in the extract and their amounts varied depending on the extraction conditions. The green bell pepper polysaccharides demonstrated antioxidant and emulsifying activities and could also be used adequately to stabilise oil/water emulsion systems. This finding shows that green bell pepper could be used as an alternative source of antioxidants and an emulsifier/stabilising agent, and furthermore, the extraction conditions could be fine-tunned to produce polysaccharides with the desired quality depending on their application.

Macromol doi: 10.3390/macromol4020023

Authors: Maria-Beatrice Coltelli Vito Gigante Laura Aliotta Andrea Lazzeri

The present chapter focuses on the recyclability of both renewable and biodegradable plastics, considering the recovery of matter (mechanical or chemical recycling) from the polymeric materials currently most diffused on the market. Biobased and compostable plastics are carbon neutral; thus, they do not contribute significantly to greenhouse gas (GHG) emissions. Nevertheless, recycling can be beneficial because it allows a prolongation of the material life cycle so that carbon is stored for a longer time up to the final composting. The chemical or mechanical recycling option is linked both to the possibility of reprocessing bioplastics without detrimental loss of properties as well as to the capability of selecting homogenous fractions of bioplastics after waste collection. Moreover, the different structural features of biodegradable bioplastics have resulted in different chemical recycling opportunities and also in different behaviors during the reprocessing operations necessary for recycling. All these aspects are discussed systematically in this review, considering biodegradable bioplastics, their blends and composites with natural fibers.

Macromol doi: 10.3390/macromol4020022

Authors: Alla P. Toropova Andrey A. Toropov Alessandra Roncaglioni Emilio Benfenati

The inhibitory activity of peptides on angiotensin-converting enzyme (ACE) is a measure of their antihypertensive potential. Quantitative structure–activity relationship (QSAR) models obtained based on the analysis of sequences of amino acids are suggested. The average determination coefficient for the active training sets is 0.36 ± 0.07. The average determination coefficient for validation sets is 0.79 ± 0.02. The paradoxical situation is caused by applying the vector of ideality of correlation, which improves the statistical quality of a model for the calibration and validation sets but is detrimental to the statistical quality of models for the training sets.

Macromol doi: 10.3390/macromol4020021

Authors: Yusuke Yamashita Yoshihiro Ohzuno Masahiro Yoshida Takayuki Takei

Conventionally, chitosan hydrogels are acidic and contain toxic chemicals because chitosan is soluble only in acidic solvents and requires toxic additives such as chemical crosslinkers and polymerization agents to fabricate chitosan hydrogels. These properties prevent chitosan hydrogels from being used for medical applications. In this study, chitosan hydrogels were prepared by a simple and versatile process using urea hydrolysis by autoclaving (steam sterilization, 121 °C, 20 min). When autoclaved, urea hydrolyzes in an acidic chitosan aqueous solution, and ammonia is produced, which increases the pH of the solution, and chitosan becomes insoluble, leading to the formation of a chitosan hydrogel. The pH and osmotic concentration of chitosan hydrogels could be adjusted to be suitable for physiological conditions (pH: 7.0–7.5, and osmotic concentration: 276–329 mOsm/L) by changing the amount of urea added to chitosan solutions (chitosan: 2.5% (w/v), urea: 0.75–1.0% (w/v), pH: 5.5). The hydrogels had extremely low cytotoxicity without the washing process. In addition, not only pure chitosan hydrogels, but also chitosan derivative hydrogels were prepared using this method. The autoclaving technique for preparing low-toxic and wash-free sterilized chitosan hydrogels in a single step is practical for medical applications.

Macromol doi: 10.3390/macromol4020020

Authors: Tayssir Hamieh

This research was devoted to study the effect of the tacticity on the surface physicochemical properties of PMMA. (1) Background: The determination of the surface free energy of polymers is generally carried out by inverse gas chromatography (IGC) at infinite dilution. The dispersive, polar and surface acid-base properties of PMMA at different tacticities were obtained via IGC technique with the help of the net retention time and volume of adsorbed. (2) Methods: The London dispersion equation was used to quantify the polar free energy of adsorption, while the London dispersive surface energy γsd(T) of PMMAs was determined using the thermal model. (3) Results: The results showed non-linear variations of γsd(T) of atactic, isotactic, and syndiotactic PMMAs with three maxima characterizing the three transition temperatures of PMMAs. The obtained values of the enthalpic and entropic Lewis’s acid-base parameters showed that the basicity of the atactic PMMA was about four times larger than its acidity. (4) Conclusions: A large difference in the behavior of the various PMMAs was proven in the different values of the polar acid and base surface energies of the three PMMAs with an important effect of the tacticity of PMMA on its acid-base surface energies.

Macromol doi: 10.3390/macromol4020019

Authors: Cristiana Oliveira José A. Teixeira Nelson Oliveira Sónia Ferreira Cláudia M. Botelho

The delivery of therapeutical molecules through the skin, particularly to its deeper layers, is impaired due to the stratum corneum layer, which acts as a barrier to foreign substances. Thus, for the past years, scientists have focused on the development of more efficient methods to deliver molecules to skin distinct layers. Microneedles, as a new class of biomedical devices, consist of an array of microscale needles. This particular biomedical device has been drawing attention due to its ability to breach the stratum corneum, forming micro-conduits to facilitate the passage of therapeutical molecules. The microneedle device has several advantages over conventional methods, such as better medication adherence, easiness, and painless self-administration. Moreover, it is possible to deliver the molecules swiftly or over time. Microneedles can vary in shape, size, and composition. The design process of a microneedle device must take into account several factors, like the location delivery, the material, and the manufacturing process. Microneedles have been used in a large number of fields from drug and vaccine application to cosmetics, therapy, diagnoses, tissue engineering, sample extraction, cancer research, and wound healing, among others.

Macromol doi: 10.3390/macromol4020018

Authors: Myrsini Papageorgiou Konstantinos N. Maroulas Eleni Evgenidou Dimitrios N. Bikiaris George Z. Kyzas Dimitra A. Lambropoulou

Pharmaceuticals are used to improve the lives of people across the globe. The high demand for their fabrication and use causes a very serious environmental threat since their presence is ubiquitous in aqueous matrices. For this reason, the synthesis, characterisation, and efficiency of three chitosan-based materials to eliminate pharmaceutical mixtures from aqueous solutions were examined in the present study. The target mixture comprised seven widely used drugs: carbamazepine, cyclophosphamide, adefovir, levofloxacin, metronidazole, glibenclamide, and trimethoprim. The grafting of poly(ethylene imine) and poly(acrylamide) on the chitosan structure allowed its physical characteristics to be controlled. An adsorption assessment was performed at different pH values, and it was concluded that pH = 4 was the optimum value. The adsorption kinetics revealed that the adsorption of a drug mixture involves a combination of physical and chemical adsorption. The adsorption process appeared to be finished after 1 h for all compounds of the studied mixture, with CS-AMI exhibiting the fastest kinetics. Mass adsorption experiments were also carried out to determine its effects. Overall, the grafting process significantly increased the adsorption capacity over the pristine material. Specifically, the highest capacity increase for CS-PEI was ~220% for carbamazepine, and for CS-AMI, it was 158% for trimethoprim. FT-IR, SEM, and XRD were used for the characterisation of the polymers. Based on the findings, the three materials are suggested as very effective adsorbents for the elimination of medicine residues from aqueous matrices.

Macromol doi: 10.3390/macromol4020017

Authors: Lillian Tsitsi Mambiri Gabrielle Broussard Ja’Caleb Smith Dilip Depan

Polymer composites with exceptional bioactivity and controlled in vitro degradation are crucial in tissue engineering. A promising approach involves combining graphene oxide nanoscrolls (GONSs) and nanohydroxyapatite (nHA) with polycaprolactone (PCL). The synergy of these components enables the mineralization of nHA within GONSs through a two-step process: first, oxygen-containing anionic groups in the GONSs anchor Ca2+ ions, followed by the formation of dispersed nHA through chelation with CaHPO42− via electrovalent bonding. A thermal analysis of the scaffolds’ morphology and microstructure was conducted via DSC and SEM imaging. Its enhanced physical properties are attributed to interactions between PCL and nHA–GONSs, as confirmed by an FTIR analysis showing strong interfacial bonding. Enzymatic degradation studies demonstrated reduced weight loss in PCL–nHA–GONS composites over 21 days, highlighting GONSs’ role in enhancing dimensional stability and reinforcement. An EDS analysis post-degradation revealed increased Ca2+ deposition on scaffolds with nHA–GONSs, indicating improved biopolymer–bioceramic interaction facilitated by the GONSs’ scrolled structure. This research offers a straightforward yet effective method for functionalizing GONSs with biologically beneficial nHA, potentially advancing graphene-based biomaterial development.

Macromol doi: 10.3390/macromol4020016

Authors: Ana M. Díez-Pascual

Almost four years have passed since I was appointed editor of the journal Macromol [...]

Macromol doi: 10.3390/macromol4020015

Authors: Pedro V. Rodrigues M. Cidália R. Castro Ana M. S. Soares Liliana Melro Ana V. Machado

In this study, a material based on polyethylene (PE) and microcrystalline cellulose (MC) was developed as a breathable packaging film. Surface functionalization of MC with 3-aminopropyltriethoxysilane (APTES) has been shown to be an efficient option to tailor their properties and increase opportunities for the application of MC on the reinforcement of polymers such as polyethylene (PE). The functionalization of MC with the mentioned silane derivative was achieved using a green method and later used in the development of composites with PE in three percentages (1, 3, and 5%). All the materials were prepared by melt blending and characterized in terms of structural properties (ATR-FTIR and FTIR in transmittance mode, EDX, and SEM), thermal properties (DSC and TGA), thermomechanical properties (DMA), contact angle measurements and permeability to water vapor. The materials demonstrated the potential to be used as breathable film packaging for fresh products.

Macromol doi: 10.3390/macromol4020014

Authors: Rita Lopes Paulo M. Gordo Benilde F. O. Costa Patrícia Alves

The use of scaffolds, three-dimensional porous, biodegradable and biocompatible structures, that can be produced from natural polymers, synthetics, ceramics and metals is crucial in the tissue engineering field. Chitosan is a polysaccharide of natural origin, found in the exoskeleton of marine arthropods and in the cell wall of fungi, with enormous popularity in the production of three-dimensional materials for Tissue Engineering, in particular bone repair. This polymer has several advantages in the production of these structures in bone regeneration and repair: biodegradability, biocompatibility, non-toxicity and antimicrobial properties. This study aimed to prepare porous scaffolds, for bone repair of degenerative diseases in the spine with better performance and less secondary effects, based on chitosan and another biopolymer (sodium alginate) with the incorporation of calcium phosphates (hydroxyapatite and β-tricalcium phosphate), for tissue engineering application. The obtained scaffolds were object of a detailed characterization, namely with regard to their porosity through the ethanol method, degradation, positron annihilation spectroscopy (PAS), mechanical properties, scanning electronic microscope (SEM), thermal stability through thermogravimetric analysis (TGA), chemical composition through X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results obtained showed that the different scaffolds presented pores able to support osteoid matrix growth. The crosslinking of scaffolds was also evaluated and resulted in pores with smaller dimensions and higher regularity in the chitosan-sodium alginate polymer without calcium phosphate scaffold. It was also possible to observe the effect of inorganics on mixed-matrix scaffolds, both morphologically and chemically. These scaffolds showed promising results in terms of mechanical and chemical properties, along with promising porosity for tissue regeneration applications.

Macromol doi: 10.3390/macromol4020013

Authors: Perla Y. Sauceda-Oloño Claudia V. Lopez Bhakti K. Patel Ashlyn D. Smith Rhett C. Smith

The unique properties and sustainability advantages of sulfur polymer cement have led to efforts to use them as alternatives to traditional Portland cement. The current study explores the impact of environmental stresses on the strength development of polymer composite SunBG90, a material composed of animal and plant fats/oils vulcanized with 90 wt. % sulfur. The environmental stresses investigated include low temperature (−25 °C), high temperature (40 °C), and submersion in water, hexanes, or aqueous solutions containing strong electrolyte, strong acid, or strong base. Samples were analyzed for the extent to which exposure to these stresses influenced the thermo-morphological properties and the compressional strength of the materials compared to identical materials allowed to develop strength at room temperature. Differential scanning calorimetry (DSC) analysis revealed distinct thermos-morphological transitions in stressed samples and the notable formation of metastable γ-sulfur in hexane-exposed specimens. Powder X-ray diffraction confirmed that the crystalline domains identified by DSC were primarily γ-sulfur, with ~5% contribution of γ-sulfur in hexane-exposed samples. Compressive strength testing revealed high strength retention other than aging at elevated temperatures, which led to ~50% loss of strength. These findings reveal influences on the strength development of SunBG90, lending important insight into possible use as an alternative to OPC.

Macromol doi: 10.3390/macromol4020012

Authors: Noemi Baldino Olga Mileti Mario F. O. Paleologo Francesca R. Lupi Domenico Gabriele

In recent years, the demand for foods without animal proteins has increased, both for health and ethical reasons. Replacing animal protein in foods can result in unappealing textures, hindering consumer acceptance. In this context, interfacial properties also play a crucial role in food systems like foam or emulsions. Therefore, the interfacial rheological behavior at the air–water interface of pea protein isolate (PPI) has been investigated to understand how affects food foam production. The PPI has been studied without modification and also through enzymatic treatment with transglutaminase (TG) to understand the interfacial properties of the modified proteins. Data obtained by static measurements have shown a surface activity of PPI comparable with other vegetable proteins, while the treatment with TG does not significantly alter the surface tension value and the interfacial adsorption rate. Differences have been found in the rearrangement rate, which decreases with TG, suggesting a possible crosslinking of the pea proteins. The PPI modified with TG, studied in dynamic conditions both in dilation and shear kinematics, are less elastic than PPI that is untreated but with a higher consistency, which may lead to poor foam stability. The lower complex interfacial modulus obtained under shear conditions also suggests a low long-time stability.

Macromol doi: 10.3390/macromol4020011

Authors: Rui P. Queirós Nicole Moreira Carlos A. Pinto Liliana G. Fidalgo Jorge A. Saraiva José A. Lopes-da-Silva

This study investigated the effects of high-pressure processing (HPP; 600 MPa/15 min) and microbial transglutaminase-catalyzed (MTG; 30 U·g of protein−1) crosslinking on the concentration of dissolved proteins (SOL), free sulfhydryl groups (SH), surface hydrophobicity (H0), and viscosity of pea protein isolates (PPI) at different concentrations (1–13%; w/v). The SOL increased by increasing protein concentration (max. 29%). MTG slightly affected SOL. HPP decreased SOL with increasing protein concentration, and the combination MTG + HPP resulted in a lower SOL than HPP alone. The concentration of SH in untreated PPI increased with increasing protein concentration, reaching a maximum of 8.3 μmol·mg prot−1. MTG increased SH at higher protein concentrations. HPP lowered SH, but its concentration increased by increasing protein concentration. HPP + MTG offset the effect of MTG, yielding lower SH. MTG did not affect H0 at 1% concentration but increased it for concentrations from 3–5%, and there was a decrease with 7–9%. HPP increased H0 up to 37% for intermediate protein concentrations but did not affect it at higher concentrations. MTG + HPP decreased H0 at all protein concentrations. The viscosity of the dispersions increased with protein concentration. HPP increased the viscosity of the dispersions for concentrations above 7%, while MTG only caused changes above 9%. Combined MTG + HPP resulted in viscosity increase. The results underscore the opportunity for innovative development of high-protein products with improved properties or textures for industrial application.

Macromol doi: 10.3390/macromol4020010

Authors: Hossein Omidian Niloofar Babanejad

This review delves into the cutting-edge field of bioinspired polymer composites, tackling the complex task of emulating nature’s efficiency in synthetic materials. The research is dedicated to creating materials that not only mirror the strength and resilience found in natural structures, such as spider silk and bone, but also prioritize environmental sustainability. The study explores several critical aspects, including the design of lightweight composites, the development of reversible adhesion methods that draw inspiration from nature, and the creation of high-performance sensing and actuation devices. Moreover, it addresses the push toward more eco-friendly material practices, such as ice mitigation techniques and sustainable surface engineering. The exploration of effective energy storage solutions and the progress in biomaterials for biomedical use points to a multidisciplinary approach to surpass the existing barriers in material science. This paper highlights the promise held by bioinspired polymer composites to fulfill the sophisticated needs of contemporary applications, highlighting the urgent call for innovative and sustainable advancements.

Macromol doi: 10.3390/macromol4020009

Authors: Gabriella Guelfi Camilla Capaccia Polina Anipchenko Francesco Ciancabilla Oommen Podiyan Oommen Antonello Bufalari Massimo Zerani Margherita Maranesi

MiRNA-based therapies represent an innovative and promising strategy applicable to various medical fields, such as tissue regeneration and the treatment of numerous diseases, including cancer, cardiovascular problems, and viral infections. MiRNAs, a group of small non-coding RNAs, play a critical role in regulating gene expression at the post-transcriptional level and modulate several signaling pathways that maintain cellular and tissue homeostasis. The clinical trials discussed in the review herald a new therapeutic era for miRNAs, particularly in tissue engineering, using synthetic exogenous mimic miRNAs and antisense miRNAs (anti-miRNAs) to restore tissue health. This review provides an overview of miRNAs’ biogenesis, mechanism of action, regulation, and potential applications, followed by an examination of the challenges associated with the transport and delivery of therapeutic miRNAs. The possibility of using viral and non-viral vectors that protect against degradation and ensure effective miRNA delivery is highlighted, focusing on the advantages of the emerging use of 3D biomaterial scaffolds for the delivery of mimic miRNAs and anti-miRNAs to facilitate tissue repair and regeneration. Finally, the review assesses the current landscape of miRNA-activated scaffold therapies on preclinical and clinical studies in bone, cartilage, and skin tissues, emphasizing their emergence as a promising frontier in personalized medicine.

Macromol doi: 10.3390/macromol4010008

Authors: Elaine Halligan Billy Shu Hieng Tie Declan Mary Colbert Mohamad Alsaadi Shuo Zhuo Gavin Keane Luke M. Geever

The design and manufacturing of objects in various industries have been fundamentally altered by the introduction of D-dimensional (3D) and four-dimensional (4D) printing technologies. Four-dimensional printing, a relatively new technique, has emerged as a result of the ongoing development and advancements in 3D printing. In this study, a stimulus-responsive material, N-Vinylcaprolactam-co-DEGDA (NVCL-co-DEGDA) resin, was synthesised by Stereolithography (SLA) 3D printing technique. The N-Vinylcaprolactam-co-DEGDA resins were initiated by the Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO) photoinitiator. A range of Di(ethylene glycol) diacrylate (DEGDA) concentrations in the NVCL-co-DEGDA resin was explored, ranging from 5 wt% to 40 wt%. The structural properties of the 3D printed objects were investigated by conducting Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR-FTIR). Additionally, the 3D printed samples underwent further characterisation through differential scanning calorimetry (DSC) and swelling analysis. The results revealed an inverse relationship between DEGDA concentration and Tg values, indicating that higher concentrations of DEGDA resulted in lower Tg values. Additionally, the pulsatile swelling studies demonstrated that increasing DEGDA concentration prolonged the time required to reach the maximum swelling ratio. These findings highlight the influence of DEGDA concentration on both the thermal properties and swelling behaviour of 3D printed samples.

Macromol doi: 10.3390/macromol4010007

Authors: Giulia Leni Lorenzo Del Vecchio Claudia Dellapina Vita Maria Cristiana Moliterni Augusta Caligiani Martina Cirlini

Black soldier fly larvae (BSFL) represent a way of converting organic substrates into valuable biomolecules, and are potentially exploitable as feed and food. In the present work, BSFL grown on retted hemp fiber were chemically analyzed to evaluate their nutritional profile. Chemical analysis revealed BSFL biomass to be an interesting source of proteins (40% on dry matter) rich in essential amino acids. In addition, larval biomass contained 12% fat, mainly composed of saturated fatty acids, and β-sitosterol and campesterol were found to be the most abundant among sterols. A total of 9% of the larval biomass was composed of chitin. The investigation extended to the enzymatic hydrolysis of proteins, leading to the identification of potential bioactive peptides. Peptidomics analysis coupled with in silico tools unveiled promising antioxidant, ACE-inhibitory, and DPP-IV-inhibitory properties within the protein hydrolysates. These findings revealed the potential of BSFL grown on retted hemp fiber as a source of dietary compounds as well as bioactive molecules which can be exploited as functional ingredients in the feed and food sectors.

Macromol doi: 10.3390/macromol4010006

Authors: Kana Uchiyama Hiromichi Asamoto Hiroaki Minamisawa Kazunori Yamada

Porous cellulose beads were quaternized with glycidyltrimethylammonium chloride (GTMAC), and the potential use of the quaternized cellulose beads as an adsorbent was explored for the removal of humic acid (HA) from aqueous media. The introduction of quaternary ammonium groups was verified by FT-IR and XPS analyses, and their content increased to 0.524 mmol/g-Qcell by increasing the GTMAC concentration. The adsorption capacity of the HA increased with decreasing initial pH value and/or increasing content of quaternary ammonium groups, and a maximum adsorption capacity of 575 mg/g-Qcell was obtained for the quaternized cellulose beads with a content of quaternary ammonium groups of 0.380 mmol/g-Qcell. The removal % value increased with increasing dose of quaternized cellulose beads, and HA was highly removed at higher quaternary ammonium groups. The kinetics of the HA adsorption in this study followed a pseudo-second-order equation, and the process exhibited a better fit to the Langmuir isotherm. In addition, the k2 value increased with increasing temperature. These results emphasize that HA adsorption is limited by chemical sorption or chemisorption. The quaternized cellulose beads were repetitively used for the adsorption of HA without appreciable loss in the adsorption capacity. The empirical, equilibrium, and kinetic aspects obtained in this study support that the quaternized cellulose beads can be applied to the removal of HA.

Macromol doi: 10.3390/macromol4010005

Authors: Brian F. Dillman Sage M. Schissel Julie L. P. Jessop

Hybrid epoxide–acrylate photopolymerization enables the temporal structuring of polymer networks for advanced material properties. The ability to design polymer network architectures and to tune mechanical properties can be realized through the control of the cationic active center propagation reaction (active chain end mechanism) relative to the cationic chain transfer reaction (activated monomer mechanism). Grafted polymer networks (GPNs) can be developed through the covalent bonding of epoxide chains to acrylate chains through hydroxyl substituents, making hydroxyl-containing acrylates a promising class of chain transfer agents. This work demonstrates the formation of these GPNs and explores the physical properties obtained through the control of hydroxyl content and hybrid formulation composition. The GPNs exhibit a lower glass transition temperature than the neat epoxide network and result in a more homogeneous network. Further investigations of hydroxyl-containing acrylates as chain transfer agents will generate a wider range of physical property options for photopolymerized hybrid coatings, sealants, and adhesives.

Macromol doi: 10.3390/macromol4010004

Authors: Mahboubeh Ahmadi Bonakdar Denis Rodrigue

Electrospinning is a simple and affordable method of producing nanofibers, offering a large specific surface area and highly porous structures with diameters ranging from nanometers to micrometers. This process relies on an electrostatic field, providing precise control over the fiber dimensions and morphologies through parameter optimization and the use of specialized spinnerets and collectors. The paper extensively covers the electrospinning process and parameters, shedding light on the factors influencing electrospinning. It addresses the morphological and structural aspects of electrospun fibers that are used in different applications. Additionally, this paper explores various polymeric and non-polymeric materials used in electrospinning. Furthermore, it investigates the incorporation of fillers during electrospinning, using an electric field to enhance properties and functionality. The review concludes by offering insights into upscaling electrospinning production.

Macromol doi: 10.3390/macromol4010003

Authors: Christina Samiotaki Evangelia Tarani Dimitra Karavasili Alexandra Zamboulis Konstantinos Chrissafis Dimitrios N. Bikiaris

In the present research work, calcium pimelate (CaPim) was synthesized and investigated as an additive for high-density polyethylene (HDPE). HDPE/CaPim nanocomposites were prepared by melt-mixing, with CaPim content ranging from 0.1% to 1%, affording white homogeneous materials. The chemical structure of the nanocomposites and the incorporation of CaPim was confirmed by infrared spectroscopy. The surficial morphology and the additive distribution were examined by scanning electron microscopy. Differential scanning calorimetry and X-ray diffraction measurements showed that the thermal transitions and crystal structure of HDPE are not affected by the incorporation of CaPim, while the mechanical properties are retained overall. This study focuses on the thermal degradation of HDPE nanocomposites, investigating the degradation mechanism and kinetic parameters through various analytical methods. Isoconversional techniques, including the Friedman method, Vyazovkin analysis, and Ozawa Flynn Wall analysis, were employed to calculate activation energies (Eα). The degradation mechanism and kinetic triplet were determined based on a multivariate non-linear regression method (model-fitting). Finally, the presence of a CaPim additive was shown to increase the Eα of thermal degradation, consistent with the calculated dependence of Eα on the degree of conversion and the improved thermal stability of the HDPE matrix.

Macromol doi: 10.3390/macromol4010002

Authors: Jelica Kovačević Thomas Bechtold Tung Pham

Plant-based proteins are important macronutrients in the human diet, crucial for cell development in our bodies and for supporting the immune system. Given their nutritional and functional properties, plant-based proteins are excellent candidates for the development of plant-based food. Among other things, plant-based cheese has been identified as a potential enabler for future innovation through improvements in ingredient technology. Unlike traditional dairy cheeses, plant-based cheeses are made from a variety of ingredients such as nuts and legumes that can be fortified with nutrients also found in traditional cheese. Of course, plant-based cheeses still have some nutritional drawbacks, and most of them are processed, which means they contain preservatives, colour additives and high sodium content. Nevertheless, the physicochemical and functional properties of plant-based proteins are of great interest to the food industry and the initial interest in natural sources of plant proteins has recently shifted to the field of modification and processing. This review discusses the natural sources and classification of plant-based proteins and summarises recent studies on processing methods in the production of plant-based cheese.

Macromol doi: 10.3390/macromol4010001

Authors: Toshihiko Matsumoto

Hexakis(2-alkoxy-1,5-phenyleneimine) macrocycles were synthesized using a simple one-pot procedure through precipitation-driven cyclization. The acetal-protected AB–type monomers, 2-alkoxy-5-aminobenzaldehyde diethyl acetals, underwent polycondensation in water or acid-containing tetrahydrofuran. The precipitation–driven cyclization, based on imine dynamic covalent chemistry and π–stacked columnar aggregation, played a decisive role in the one–pot synthesis. The progress of the reaction was analyzed using MALDI–TOF mass spectrometry. The macrocycles with alkoxy chains were soluble in specific organic solvents, such as chloroform, allowing their structures to be analyzed using NMR. The shape-anisotropic, nearly planar, and shape-persistent macrocycles aggregated into columnar assemblies in polymerization solvents, driven by aromatic π-stacking. The octyloxylated macrocycle OcO–Cm6 exhibited an enantiotropic columnar liquid crystal-like mesophase between 165 °C and 197 °C. In the SEM image of (S)-(–)-3,7-dimethyloctyloxylated macrocycle (–)BCO–Cm6, columnar substances with a diameter of 200–300 nm were observed. The polymerization solution for the 2-(2-methoxyethoxy)ethoxy)ethoxylated macrocycle (TEGO–Cm6) gelled, and showed thixotropic properties by forming a hydrogen bond network.

Macromol doi: 10.3390/macromol3040046

Authors: Natalia Santos Luthary Segura Amber Lewis Thuong Pham Kwan H. Cheng

The disruption of cell membranes by tau and amylin oligomers is linked to amyloid diseases such as Alzheimer’s and diabetes, respectively. The recent studies suggest that misfolded tau and amylin can form neurotoxic hetero-oligomers that are structurally different from homo-oligomers. However, the molecular interactions of these hetero-oligomers with the neuronal membranes remain unclear. Using MD simulations, we have investigated the binding behaviors, membrane disruption, and protein folding of hetero-oligomers on a raft membrane containing phase-separated lipid nanodomains like those found in neurons. We discovered that the hetero-oligomers bind to the liquid-order and liquid-disorder phase boundaries of the raft membrane. The major lipid-binding sites of these interactions include the L16 and I26 residues of amylin and the N-terminal of tau. Strong disruptions of the raft domain size by the hetero-tetramer were detected. Furthermore, the hetero-dimer disrupted the saturated phospholipid orientational order to a greater extent than the individual tau or amylin monomer. In addition, the constituent tau more strongly promoted the alpha-helix to the beta-sheet transition of the constituent amylin within the hetero-dimer when compared with the amylin monomer alone. Our results provide new molecular insights into understanding the neurotoxicity of the hetero-oligomers associated with the cross-talk between amyloid diseases.

Macromol doi: 10.3390/macromol3040045

Authors: Junjie Jiang Liang Wang Fangwei Tian Yaozong Li Wentao Zhai

The diverse physical appearances and wide density range of polymer bead foams offer immense potential in various applications and future advancements. The multiscale and multilevel structural features of bead foams involve many fundamental scientific topics. This review presents a comprehensive overview of recent progress in the preparation and molding techniques of bead foams. Firstly, it gives a comparative analysis on the bead foam characteristics of distinct polymers. Then, a summary and comparison of molding techniques employed for fabricating bead foam parts are provided. Beyond traditional methods like steam-chest molding (SCM) and adhesive-assisted molding (AAM), emerging techniques like in-mold foaming and molding (IMFM) and microwave selective sintering (MSS) are highlighted. Lastly, the bonding mechanisms behind these diverse molding methods are discussed.

Macromol doi: 10.3390/macromol3040044

Authors: Mohsen Sadeghi-Shapourabadi Said Elkoun Mathieu Robert

Nanofibrillated cellulose was extracted from potato peel waste using a fast and green method with a simple process. To extract cellulose and eliminate non-cellulosic constituents, alkaline and hydrogen peroxide treatments were performed under microwave irradiation. The nanofibrillated cellulose was extracted from purified cellulose via TEMPO oxidation followed by ultrasonication. The TEM, FTIR, XRD, and TGA experiments were used to evaluate the structural, crystalline, and thermal properties of cellulose fiber and nanofiber. The chemical and FTIR analysis of bleached fibers indicates that almost all non-cellulosic components of biomass have been eliminated. The diameter of the extracted nanofibers is in the range of 4 to 22 nm. In terms of crystallinity, extracted nanocellulose had 70% crystallinity, compared to 17% for unprocessed lignocellulose fibers, which makes it an excellent choice for use as a reinforcement phase in biobased composites. Thermogravimetric analysis reveals that cellulose nanofibers are less thermally stable than potato peel pure cellulose, but it has a higher char content (28%) than pure cellulose (6%), which signifies that the carboxylate functionality acts as a flame retardant. The comparison between cellulose derived from microwave and conventional extraction methods confirmed that their impact on the removal of non-cellulosic materials is nearly identical.

Macromol doi: 10.3390/macromol3040043

Authors: Christoph Burgstaller Károly Renner

Wood–plastic composites, consisting of wood particles and a thermoplastic matrix, are common composites often used in buildings as decking boards or for similar non-load-carrying applications. As these are usually semi-finished products, a certain amount of material is available after cutting these to size, in the factory and also at installation sites. Especially for in-house waste streams in factories, the question remains whether these materials can be reprocessed without any negative influence on the materials’ properties. Therefore, the aim of this work is to investigate the influence of reprocessing on the property profile of polypropylene based wood–plastic composites. Two base formulations with 40 wt% of wood particles and two different polypropylene grades were investigated for their mechanical properties, wood particle size, color, weathering stability and water uptake. We found that most of the wood–plastic composites’ properties were not negatively influenced by the multiple processing steps; the most pronounced effect beside particle size reduction is color degradation, as the composites darken with increasing number of processing steps. In our opinion this shows, that wood–plastic composites can be recycled, especially if these are only reprocessed in smaller shares together with virgin materials.

Macromol doi: 10.3390/macromol3040042

Authors: Yutaka Ohsedo Honoka Murata

It is widely known that skin irritation can be induced by interactions between polymer fibers constituting clothing and the skin, leading to skin inflammation and unfavorable dermatological reactions. Thus, significant endeavors have been directed toward ameliorating this phenomenon. This study engineered synthetic fibers with reduced potential for skin irritation. This was achieved via a strategy inspired by the inherent smoothness of silk fibers, which exhibit minimal friction and irritation against the skin. This investigation focused on urethane fibers, a class of synthetic fibers frequently used in textile applications. Hydrogel cross-linked polyurethane–urea fibers were subjected to controlled swelling in different hydrophilic mixed-solvent environments. Subsequent freeze-drying procedures were employed to yield fibers with diverse surface morphologies and encompassing features such as elevations and creases. The correlation between the compositions of the solvent mixtures used and the resulting surface morphologies of the fibers was rigorously assessed through polarized light and scanning electron microscopies. Additionally, the interplay between the degree of swelling and the tensile strength of the fabricated fibers was comprehensively analyzed. Consequently, the methodological combination of swelling and freeze-drying endowed the polyurethane–urea fibers with various surface profiles. Future studies will delve into the intricate connection between fiber surface characteristics and their potential to induce skin irritation. It is envisaged that such investigations will substantially contribute to the refinement of textile fibers designed for enhanced compatibility with the skin.

Macromol doi: 10.3390/macromol3040041

Authors: Agnieszka Folentarska Anna Kulakowska Volodymyr Pavlyuk Magdalena Krystyjan Piotr Tomasik Wojciech Ciesielski

Fully biodegradable foils were prepared from potato starch, egg albumin, and either stearic or oleic acid. Foils prepared with oleic acid have higher tensile strength, relative elongation, thermal stability, and a more uniform macrostructure. Foils produced with stearic acid were characterized by a higher index of crystallinity than foils made with oleic acid. Functional properties of the foils can be modulated involving a sequence of blending of their components. The simultaneous blending of starch (10 weight parts of 5% aq. gel), albumin (1 weight part of liquid composed of 1 g of albumin in 7 mL of water), and stearic acid (5 weight parts of powder) provided the foil with the highest tensile strength (64.91 MPa/mm). Independently of the method of preparation, foils were white with a greenish-yellow shade. Analysis of the ATR-FTIR spectra showed that the macrostructure of the foils is built involving interactions between all three components.

Macromol doi: 10.3390/macromol3040040

Authors: Sofia J. Silva Nsevolo Samba José Mendes João R. A. Pires Carolina Rodrigues Joana Curto Arlindo Gomes Ana Luísa Fernando Lúcia Silva

Active packaging with biobased polymers aim to extend the shelf life of food and to improve the environmental sustainability of the food industry. This new concept was tested with samples of fresh poultry meat wrapped with chitosan reinforced with 2.5% of commercial nanocellulose (NC) incorporating 1% of essential oils (EO) from Aloysia citrodora (ACEO) and Cymbopogon citratus (CCEO). The performance of the bionanocomposites containing EOs was assessed and compared with unwrapped meat samples and samples wrapped with chitosan/NC, during a 13 day period of refrigerated storage for several physicochemical parameters related to food deterioration and microbial growth. Wrapping the meat with the chitosan/NC polymer helped to increase the shelf life of the meat. The incorporation of EOs added extra activity to the biocomposites, further delaying the meat deterioration process, by halting the lipid oxidation and the Enterobactereaceae growth until the 9th day. The composition of both EOs was similar, with the main components contributing to the increased activity of the biopolymers being geranial and neral. The performance of ACEO surpassed that of CCEO, namely on the Enterobactereaceae growth. This trend may be associated with ACEO’s higher phenolic content and the higher antioxidant activity of the compounds released by the ACEO biopolymers.

Macromol doi: 10.3390/macromol3040039

Authors: Ivan Malenica Marina Golik Krizmanić Marina Vukoje Rahela Kulčar Katarina Itrić Ivanda

During its life cycle, packaging comes into contact with various substances and even those it protects. Thus, for example, oil, water, and alcohol, if spilled on the packaging, can damage its functionality. In addition to exposure to chemicals, graphic products (packaging) can be exposed to moisture and UV radiation, which can negatively affect their stability during transport, storage, and handling. The choice of printing substrate can directly affect the stability of prints against different degrading influences. This paper explores the stability of thermochromic (TC) and conventional offset printing inks printed on environmentally friendly printing substrates intended for packaging applications (labelling). Results have confirmed that used printing substrates and printing inks give prints good rub resistance, but somewhat lower stability in terms of ethanol, water, and UV radiation. The choice of printing substrate can directly affect the stability of prints against different degrading influences. The resistance of prints to oil cannot be clearly defined since the samples were altered with the coloration of the oil. It can only be stated that oil reduced the functionality of the TC prints given that the samples were colored by the oil itself.

Macromol doi: 10.3390/macromol3040038

Authors: Charini P. Maladeniya Nawoda L. Kapuge Dona Ashlyn D. Smith Rhett C. Smith

A series of six composites was prepared from the reaction of lignin-derived guaiacol, fatty acids, and sulfur. In this preparation, the organic comonomers undergo C–S bond-forming reactions to establish a highly crosslinked network material in which some non-covalently incorporated sulfur species are also entrapped. Both monounsaturated oleic acid and diunsaturated linoleic acid were used as fatty acid components to assess the influence of their unsaturation levels on composite properties. The ratio of organics and the proportion of sulfur (70 or 80 wt%) was also varied to assess the effect on thermal, morphological, and mechanical properties. Thermogravimetric analysis showed that composites exhibited good thermal stability up to ~220 °C. Differential scanning calorimetry revealed that the materials generally exhibit melting features for entrapped cyclo-S8, cold crystallization features for some materials, and a composition-dependent glass transition temperature. The flexural and compressive strengths of the composites revealed that some of the composites exhibit strengths significantly higher than those required of Portland cements used in residential housing fabrication and may be more sustainable structural materials. The thermal and mechanical properties could be tailored by changing the degree of unsaturation of the fatty acid comonomer or by altering the percentage of fatty acid in the monomer feed. The highest mechanical strength was achieved with greater amounts of monounsaturated oleic acid comonomer.

Macromol doi: 10.3390/macromol3030037

Authors: Antonella Patti Domenico Acierno

Fabrics have been recognized as a necessary component of daily life due to their involvement in garments, home textiles, and industrial textiles. The mechanical performance of textiles was considered essential to meet the end-user requirements for strength and durability. The purpose of this work was to provide an overview of the textile structures and tensile strengths of woven textiles. Different types of textile structures, depending on the weaving methods (woven, braided, knitted, non-woven) and the most common architectures of woven fabrics (plain weave, twill and sateen), were presented. Common materials constituting the textiles’ structures and a comparison in terms of the density, Young’s modulus and tensile strength between natural (plant-based, animal-based, and mineral-based) and synthetic fibers were reported. The mechanical properties of woven textiles were presented for neat and coated textiles, primarily in terms of the tensile strength. Depending on the cases, typical regions in the load–displacement curve (i.e., crimp, elastic, non-linear failure, thread fracture) were highlighted. The impact of the architecture, yarn distance and size, and yarn twisting on the tensile strength of woven fabrics was then illustrated.

Macromol doi: 10.3390/macromol3030036

Authors: Shunsuke Mizutani Shunya Kita Naoya Sakai Takuya Yamamoto Andrej Koleżyński Toyoji Kakuchi Shin-ichiro Sato

Aqueous solutions of conventional temperature-responsive amphiphilic polymers undergo a coil–globule conformational transition around the lower critical solution temperature (LCST) that causes the polymer surfaces to become hydrophobic and the polymers to aggregate together. Isocyanate polymers with alkylated oligo(ethylene oxide) side chains are expected to have rigid main chains and, thus, do not undergo the coil–globule structural transition, but they have recently been reported to exhibit temperature-responsive properties. In this study, molecular dynamics was used to calculate the agglomeration tendencies of two chains of poly(alkylated tri(ethylene oxide)isocyanate) (PRTEOIC, where R = methyl (Me) or ethyl (Et)) in aqueous solution to elucidate the LCST phenomenon in the absence of coil–globule conformational transition. Our MD simulations showed that aggregation also occurs in rod polymers. Furthermore, we found that both (PMeTEOIC)2 and (PEtTEOIC)2 showed parallel agglomeration of the two molecular chains with increasing temperature, but only (PMeTEOIC)2 showed a metastable T-shaped agglomeration in the middle temperature range. The crossing-point temperature (TCRP) at which the density of the first hydrophobic hydration shell around the sidechain alkyl group equals the bulk water density is a useful indicator for predicting the LCST of rod polymers with dense side chains terminated by alkyl groups.

Macromol doi: 10.3390/macromol3030035

Authors: Evangelia C. Vouvoudi George A. Tamias Evangelia A. Chatzicharistou Dimitris S. Achilias

In the present study, the results of an experimental work on the thermal endurance and decomposition products of the commercial restorative adhesive Loctite® Super Attak Glass, being applied on glass surfaces, are presented. The clarity of the cyanoacrylate polymer and its rapid anionic polymerization reaction are outcomes of the chemistry of the monomer and its activity. First, evaluation of the reversibility of this glue was examined through the solubility tests. It was verified that the adhesive is reversible since it is diluted in several solvents. Later, by applying pyrolysis conjugated with gas chromatography and mass spectrometry (Py–GC/MS), the thermal profile of the polymer is recorded in its neat form and in its aged state (weathered under the influence of UV-irradiation or thermal treatment at 50 and 75 °C). The decomposition products are detected and identified and, finally, possible reactions are investigated. Emphasis is placed on those that could be considered harmful to cultural heritage materials and objects. The fragments by the pyrolytic reactions identified mainly concern esters, less aldehydes and alcohols, small nitrogen compounds, and in some cases unsaturated hydrocarbons with higher molecular weight. Additives such as radical polymerization inhibitors and stabilizers, as well as some plasticizers, were also detected.

Macromol doi: 10.3390/macromol3030034

Authors: Melissa García-Carrasco Octavio Valdez-Baro Luis A. Cabanillas-Bojórquez Manuel J. Bernal-Millán María M. Rivera-Salas Erick P. Gutiérrez-Grijalva J. Basilio Heredia

Chitosan is a non-toxic, biodegradable, and biocompatible natural biopolymer widely used as a nanocarrier, emulsifier, flocculant, and antimicrobial agent with potential applications in industry. Recently, chitosan has been used as an encapsulating agent for bioactive plant compounds and agrochemicals by different technologies, such as spray-drying and nanoemulsions, to enhance antimicrobial activity. Chitosan nanocomposites have been shown to increase potential biocidal, antibacterial, and antifungal activity against pathogens, presenting higher stability, decreasing degradation, and prolonging the effective concentration of these bioactive compounds. Therefore, the objective of this work is to review the most outstanding aspects of the most recent developments in the different methods of encapsulation of bioactive compounds (phenolic compounds, essential oils, among others) from plants, as well as the applications on phytopathogenic diseases (fungi and bacteria) in vitro and in vivo in cereal, fruit and vegetable crops. These perspectives could provide information for the future formulation of products with high efficacy against phytopathogenic diseases as an alternative to chemical products for sustainable agriculture.

Macromol doi: 10.3390/macromol3030033

Authors: Bénédicte Fromager Emilie Marhuenda Benjamin Louis Norbert Bakalara Julien Cambedouzou David Cornu

Electrospinning is a simple and versatile method to generate nanofibers. Remarkable progress has been made in the development of the electrospinning process. The production of nanofibers is affected by many parameters, which influence the final material properties. Electrospun fibers have a wide range of applications, such as energy storage devices and biomedical scaffolds. Among polymers chosen for biological scaffolds, such as PLA or collagen, polyacrylonitrile (PAN) has received increasing interest in recent years due to its excellent characteristics, such as spinnability, biocompatibility, and commercial viability, opening the way to new applications in the biotechnological field. This paper provides an overview of the electrospinning process of a large range of polymers of interest for biomedical applications, including PLA and PEO. It covers the main parameters and operation modes that affect nanofiber fabrication. Their biological applications are reviewed. A focus is placed on PAN fiber formation, functionalization, and application as scaffolds to allow cell growth. Overall, nanofiber scaffolds appear to be powerful tools in medical applications that need controlled cell culture.

Macromol doi: 10.3390/macromol3030032

Authors: Kazunori Yamada Yuki Kazama Yuji Kimura

This study aims to confer autohesive strength to polyethylene (PE) plates by swelling the grafted layers, which were formed on the PE plates grafted with alkyl (meth)acrylate monomers, with 1,4-dioxane, and subsequently heat-pressing them. For the methyl methacrylate (MMA)-grafted PE (PE-g-PMMA) plates, the location of grafting was restricted to the outer surface region and the grafted layer with higher densities of grafted PMMA chains was composed. When the grafted PE plates were immersed in 1,4-dioxane, and then heat-pressed while applying the load, autohesion was developed. The substrate failure was observed for the PE-g-PMMA plates and the grafted amount at which the substrate failure was observed decreased with the procedures that decreased the methanol concentration of the solvent, the MMA concentration, the grafting temperature, and the heat-press temperature, and/or increased the load. The lowest grafted amount of 45 μmol/cm2 for the substrate failure was obtained under the conditions where the PE-g-PMMA plate prepared at 0.75 M and 60 °C in a 70 vol% aqueous methanol solution was heat-pressed at 60 °C while applying the load of 2.0 kg/cm2. The swelling of the grafted layers with 1,4-dioxane considerably contributed to the development of autohesion, bringing the inter-diffusion of grafted PMMA chains and coincident entanglement of grafted PMMA chains during the heat-pressing. The fact that the substrate failure occurred indicates that an autohesive strength higher than the ultimate strength of the used PE plate was obtained. Our approach provides a novel procedure to develop the water-resistant autohesion of PE plates.

Macromol doi: 10.3390/macromol3030031

Authors: Guadalupe Gabriel Flores-Rojas Bélen Gómez-Lazaro Felipe López-Saucedo Ricardo Vera-Graziano Emilio Bucio Eduardo Mendizábal

Tissue engineering and regenerative medicine have emerged as innovative approaches to enhance clinical outcomes by addressing tissue lesions and degenerations that can significantly impair organ function. Since human tissues have limited regenerative capacity, the field of regenerative medicine aims to restore damaged tissues and their functionalities. Recent decades have witnessed remarkable progress in materials science, tissue engineering, and medicine, leading to the development of regenerative engineering. This interdisciplinary field has revolutionized the production of artificial matrices, enabling the design of anatomically accurate structures with enhanced biocompatibility, bioabsorption, and cell adhesion. Among the techniques utilized for fabricating cellular scaffolds, the electrospinning of fibers stands out as an ideal approach due to its ability to mimic the characteristics of the extracellular matrix (ECM). Electrospun scaffolds exhibit distinct advantages, including a high surface area-to-volume ratio, exceptional porosity, uniformity, compositional diversity, structural flexibility, and the ease of functionalization with bioactive molecules for controlled release. These versatile properties allow for the creation of nanofiber scaffolds that closely resemble the architecture of the ECM. Consequently, they facilitate the transport of nutrients and oxygen to cells as well as the incorporation of growth factors to stimulate cell growth. These advancements open up a wide range of applications in the field of regenerative medicine.

Macromol doi: 10.3390/macromol3030030

Authors: Manuel Adrian Picos-Salas Melissa García-Carrasco José Basilio Heredia Luis Angel Cabanillas-Bojórquez Nayely Leyva-López Erick Paul Gutiérrez-Grijalva

Polyphenols have attracted attention for their anti-inflammatory, antidiabetic, and anticancer properties. Due to the antioxidant and anti-inflammatory potential of these molecules, they are also proposed as a potential therapeutic tool to prevent complications of cancer and decrease the secondary effects of conventional chemotherapeutic drugs. Nonetheless, polyphenols such as flavonoids and phenolic acids have low bioavailability, as they are highly metabolized. Thus, administration strategies have been developed to enhance the anticancer properties of polyphenols. Most of these strategies involve different encapsulation techniques, such as nanoencapsulation, nanoemulsion, and the use of other polymeric matrixes. These techniques can increase the activity of these compounds after going through the gastrointestinal process and improve their solubility in an aqueous medium. This review comprises recent studies regarding encapsulation techniques to enhance the bioactivity of polyphenols against cancer and their current state in clinical studies. Overall, micro- and nanoencapsulation techniques with different polymers enhanced the anticancer properties of polyphenols by inhibiting tumor growth, modulating the expression of genes related to metastasis and angiogenesis, decreasing the expression of pro-inflammatory biomarkers.

Macromol doi: 10.3390/macromol3030029

Authors: Eldar A. Mamin Petr V. Pantyukhov Anatoly A. Olkhov

This review considers the recent investigations in the scope of biodegradability of synthetic polymers, spanning polyethylene (PE), polypropylene (PP), and their corresponding composites, with a focus on the influence of oxo-additives (mostly transition metal salts). The types of oxo-additives and the mechanisms of oxidation acceleration are discussed. Furthermore, the influence of oxo-additives on both physicochemical and biological stages of degradation is evaluated (laboratory and field experiments with microorganisms/fungi action) with recent standards suggested for degradation estimation. Comparisons of the metal salts are given with respect to catalysis, as well as the synergetic influence of additives. The additives presented on the commercial market are also discussed.

Macromol doi: 10.3390/macromol3030028

Authors: Xiao-Yuan Chen Denis Rodrigue

In this work, a simple and environmentally friendly process combining low pressure (vacuum) and mechanical compression is proposed to convert recycled polypropylene (PP) foams (28 kg/m3) into low density foams (90–131 kg/m3) having negative tensile and compressive Poisson’s ratios (NPR). The main objective of the work was to determine the effect of processing conditions (vacuum time, temperature and mechanical pressure). Based on the optimized conditions, the tensile Poisson’s ratio of the resulting auxetic foams reached −1.50, while the minimum compressive Poisson’s ratio was −0.32 for the same sample. The foam structure was characterized via morphological analysis (SEM) to determine any changes related to the treatment applied. Finally, the tensile and compressive properties (Young’s modulus, strain energy, energy dissipation and damping capacity) are also presented and discussed. It was observed that the mechanical properties of the resulting auxetic foams were improved compared to the original PP foam (PP-O) for all tensile properties in terms of modulus (19.9 to 59.8 kPa), strength (0.298 to 1.43 kPa) elongation at break (28 to 77%), energy dissipation (14.4 to 56.3 mJ/cm3) and damping capacity (12 to 19%). Nevertheless, improvements were also observed under compression in terms of the energy dissipation (1.6 to 3.6 mJ/cm3) and the damping capacity (13 to 19%). These auxetic foams can find applications in sport and military protective equipment, as well as any energy mitigation system.

Macromol doi: 10.3390/macromol3030027

Authors: Nataly Diniz de Lima Santos Lidiane Pereira de Albuquerque Marcus Mello Rego de Amorim Juliane Nancy de Oliveira Silva Thamara Figueiredo Procópio Patryck Érmerson Monteiro dos Santos Patrícia Maria Guedes Paiva Mercia Rodrigues Barros Thiago Henrique Napoleão Emmanuel Viana Pontual

In this study, we evaluated the susceptibility of Alphitobius diaperinus larvae and adults to saline extract (SE), lectin-rich fraction (FR), and isolated lectin (MvRL) from Microgramma vacciniifolia rhizomes. To determine immediate effects, larvae and adults were exposed to SE (10.5 mg/mL), FR (7.5 mg/mL), or MvRL (1.0 mg/mL) for 48 h. Live insects were evaluated for acetylcholinesterase (AChE) activity. The delayed effects of SE (10.5 mg/mL), FR (7.5 mg/mL), and MvRL (0.2 and 0.4 mg/mL) were checked by incubating the adults for 16 days with a diet containing the preparations. In vitro effects on gut digestive enzymes were investigated. All preparations showed immediate larvicidal effect but had no effect on adult survival. Extracts from FR-treated larvae showed higher AChE activity than control insects. In the delayed effect assay, the adults lost biomass after consuming SE and FR. FR was the most effective inhibitory agent of trypsin-like and amylase activities (88% and 65% inhibition, respectively). All preparations inhibited endoglucanase activity in 94–98%, while SE and FR inhibited exoglucanase activity in 93.2 and 94.1%, respectively. In conclusion, M. vacciniifolia rhizomes contain compounds (including MvRL) that affect the survival and physiology of A. diaperinus, acting as potential natural insecticides for controlling this pest.

Macromol doi: 10.3390/macromol3030026

Authors: Maurice Dalton Farnoosh Ebrahimi Han Xu Ke Gong Gustavo Fehrenbach Evert Fuenmayor Emma J. Murphy Ian Major

The use of biodegradable polymers in tissue engineering has been widely researched due to their ability to degrade and release their components in a controlled manner, allowing for the potential regeneration of tissues. Melt blending is a common method for controlling the degradation rate of these polymers, which involves combining these materials in a molten state to create a homogenous mixture with tailored properties. In this study, polycaprolactone (PCL) was melt blended with hydrophilic poly (ethylene oxide) (PEO) of different molecular weights to assess its effect on PCL material performance. Hydrolytic degradation, thermal and viscoelastic properties, and surface hydrophilicity were performed to contrast the properties of the blends. DSC, DMA, and FTIR were performed on selected degraded PCL/PEO specimens following mass loss studies. The results showed that adding PEO to PCL reduced its melt viscosity-torque and melt temperature while increasing its hydrophilicity, optimizing PCL/PEO blend for soft tissue engineering applications and could contribute to the development of more effective and biocompatible materials for soft tissue regeneration.

Macromol doi: 10.3390/macromol3030025

Authors: Anatoly Nikolayevich Boyandin

The degradation patterns of bacterial poly-3-hydroxybutyrate (PHB) in chloroform solution under the action of thionyl chloride in the presence of zinc chloride were studied. When 2.5.mol of zinc chloride and 100 mmol of thionyl chloride were introduced into the solution of 25 mmol PHB, a decrease in the molecular weight of the polymer was observed. During the reaction, a relatively rapid decrease in the molecular weight of the polymer was noted in the first hour of the experiment; thus, the values of the weight-average molecular weight decreased from 840 kDa to 483, 167, 58.6, and 16.7 kDa after 1, 5, 24, and 96 h of the experiment, respectively. The polydispersity also gradually decreased from 2.69 at the beginning to 1.92 at the end of the experiment. Oligomers of PHB containing 3-chlorobutyric acid and 3-hydroxybutyryl chloride residues at the O and C ends of the polymer chain, respectively, were obtained. The results confirm the ability of thionyl chloride to interact with aliphatic esters in the presence of zinc compounds, and demonstrate the possibility of using this reaction to produce oligomeric derivatives of polyesters bearing chloralkyl and acid chloride functional groups.

Macromol doi: 10.3390/macromol3020024

Authors: Cătălina Diana Uşurelu Denis Mihaela Panaitescu

Nanocellulose can be obtained from low-cost sources and has been extensively studied in the last decades due to its biodegradability, biocompatibility, low weight, large specific surface area, and good mechanical and optical properties. The nanocellulose properties palette can be greatly expanded by incorporating different metals, metal oxides or carbon nanomaterials, with the formation of multifunctional hybrids. Nanocellulose–nanocarbon hybrids are emerging nanomaterials that can respond to many current challenges in areas such as water purification, energy storage and conversion, or biomedicine for drug delivery, tissue engineering, antitumor and antimicrobial therapies, and many others. Although nanocellulose–nanodiamonds hybrids are still in their infancy, these nanomaterials are extremely promising for applications requiring good thermal conductivity and mechanical strength along with optical transparency. A strong increase in the thermal conductivity of a nanocellulose film of about 150 times was obtained after the addition of 90 wt% single-crystal nanodiamonds and a 70% increase in the Young’s modulus of nanocellulose films was produced by the addition of 5 wt% nanodiamonds. Therefore, in this review, data related to the manufacturing routes, main properties, and applications of nanocellulose–nanodiamonds hybrids are presented and discussed. This review paves the way for new methods and procedures to obtain nanocellulose–nanodiamonds hybrids better adapted to practical needs.

Macromol doi: 10.3390/macromol3020023

Authors: Rafael Resende Assis Silva Clara Suprani Marques Tarsila Rodrigues Arruda Samiris Cocco Teixeira Taíla Veloso de Oliveira

Nowadays, sustainable and biodegradable bioplastics are gaining significant attention due to resource depletion and plastic pollution. An increasing number of environmentally friendly plastics are being introduced to the market with the aim of addressing these concerns. However, many final products still contain additives or mix non-biodegradable polymers to ensure minimum performance, which often undermines their ecological footprint. Moreover, there is a lack of knowledge about all stages of biodegradation and their accuracy in classifying products as biodegradable. Therefore, this review provides an overview of biodegradable polymers, elucidating the steps and mechanisms of polymer biodegradation. We also caution readers about the growing marketing practice of “greenwashing” where companies or organizations adopt green marketing strategies to label products with more environmental benefits than they have. Furthermore, we present the main standards for evaluating biodegradation, tools, and tests capable of measuring the biodegradation process. Finally, we suggest strategies and perspectives involving concepts of recycling and the circularity of polymers to make them more environmentally friendly and sustainable. After all, “throwing away” plastics should not be an option because there is no outside when there is only one planet.

Macromol doi: 10.3390/macromol3020022

Authors: Katia Bacha Catherine Chemotti Jean-Pierre Mbakidi Magali Deleu Sandrine Bouquillon

Dendrimers are increasingly being studied in the context of encapsulation. Many potential applications of dendrimers are based on their properties. They are used in drug delivery systems, cosmetics, food and chemistry. This review is first devoted to different synthesis approaches for dendrimers and to their ability to encapsulate active molecules. Their applications in different fields, as well as their cytotoxicity, are then detailed. To conclude this review, the main works on the interaction of dendrimers with the stratum corneum (SC) are also presented.

Macromol doi: 10.3390/macromol3020021

Authors: Keran Zhou Farah Alwani Azaman Zhi Cao Margaret Brennan Fournet Declan M. Devine

A large bone defect is defined as a defect that exceeds the regenerative capacity of the bone. Nowadays, autologous bone grafting is still the gold standard treatment. In this study, a hybrid bone tissue engineering scaffold (BTE) was designed with biocompatibility, biodegradability and adequate mechanical strength as the primary objectives. Chitosan (CS) is a biocompatible and biodegradable polymer that can be used in a wide range of applications in bone tissue engineering. Hydroxyapatite (HAp) and fluorapatite (FAp) have the potential to improve the mechanical properties of CS. In the present work, different volumes of acetic acid (AA) and different ratios of HAp and FAp scaffolds were prepared and UV cross-linked to form a 3D structure. The properties of the scaffolds were characterised by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, swelling studies and compression testing. The cytotoxicity result was obtained by the MTT assay. The degradation rate was tested by weight loss after the scaffold was immersed in SBF. The results showed that a crosslinked structure was formed and that bonding occurred between different materials within the scaffold. Additionally, the scaffolds not only provided sufficient mechanical strength but were also cytocompatibility, depending on their composition. The scaffolds were degraded gradually within a 6-to-8-week testing period, which closely matches bone regeneration rates, indicating their potential in the BTE field.

Macromol doi: 10.3390/macromol3020020

Authors: Rafael Carvalho Alves Camila Ramão Contessa Caroline Costa Moraes Gabriela Silveira da Rosa

The biggest challenge for scientists is to create an ideal wound dressing that should be non-toxic, biocompatible, and biodegradable, providing optimal conditions for the most effective regeneration process. Biomaterials loaded with plant-derived compounds show better biocompatibility and biological properties, ensuring a faster tissue repair process. In order to develop membranes with good mechanical properties and anti-bacterial properties, the objective of this work describes the synthesis of a chitosan-based membrane added with olive leaf extract as an active principle with potential for topical application. The material developed was characterized in terms of morphology, physical, chemical, and mechanical properties, and the anti-bacterial capacity of the membranes. The results indicated that the developed membrane has good potential for use as a wound dressing, as it presented mechanical properties (30.17 ± 8.73 MPa) and fluid draining capacity (29.31 ± 1.65 g·m−2·h−1) adequacy. In addition, the antimicrobial activity analysis revealed the active membrane potential against E. coli and S. aureus reaching 9.9 mm and 9.1 mm, respectively, in inhibition zones, the most common bacteria in skin wounds. Therefore, all the results indicate that the developed membrane presents viable characteristics for the use of wound dressing.

Macromol doi: 10.3390/macromol3020019

Authors: Christoph Burgstaller Károly Renner

Using natural materials as reinforcements for polypropylene to alter composite properties and cost is a well-known approach. Often, wood particles are used for that. These give reasonable reinforcement, but are also sought after by other industries, e.g., for energy production, and may also not be available everywhere. Therefore, the aim of this work was to investigate cherry pit particles as an alternative material for polypropylene reinforcement. Cherry pits originate as a by-product from fruit processing and have not been utilized until now as reinforcement. Cherry pit particles were produced by milling the pits, and afterwards composites were produced by compounding and injection molding. Mechanical properties and melt flow were investigated. We found some reinforcement effect, but to a lesser extent than wood particles. The cherry pit particles contain some fatty acid components, which reduce tensile properties and increase the melt flow rate of the composites. For future applications, methods for reducing these fatty acids to improve reinforcement capabilities should be investigated.

Macromol doi: 10.3390/macromol3020018

Authors: Jéssica de Santana Brito Amanda de Oliveira Marinho Leydianne Leite de Siqueira Patriota Wyndly Daniel Cardoso Gaião Diego José Lira Torres Patrícia Maria Guedes Paiva Virgínia Maria Barros de Lorena Cláudio Gabriel Rodrigues Márcia Bezerra da Silva Thiago Henrique Napoleão

Lectins (carbohydrate-binding proteins) are able to distinguish different patterns of glycosylation on cell surfaces. This study investigated the effects of lectins from Alpinia purpurata inflorescence (ApuL) and Schinus terebinthifolia leaf (SteLL) on the viability of human leukemia cells (K562, chronic myeloid leukemia; JURKAT, acute lymphoblastic leukemia) and mesenchymal stem cells (MSCs) from human umbilical cords. In addition, possible immunomodulatory effects of ApuL and SteLL on MSCs were assessed by determining cytokine levels in cultures. ApuL reduced the viability of JURKAT cells (IC50: 12.5 μg/mL), inducing both apoptosis and necrosis. For K562 cells, ApuL at 50 µg/mL caused a decrease in viability, but of only 8.8%. Conversely, SteLL exerted a cytotoxic effect on K562 (IC50: 6.0 μg/mL), inducing apoptosis, while it was not cytotoxic to JURKAT. ApuL and SteLL (0.19–100 μg/mL) did not decrease MSCs viability. Treatment with ApuL strongly suppressed (99.5% reduction) the release of IL-6 by MSCs. SteLL also reduced the levels of this cytokine in culture supernatant. In conclusion, ApuL and SteLL showed potential to reduce the viability of leukemia cells, as well as immunomodulatory effect on MSCs without being toxic to them. These biological properties can be explored biomedically and biotechnologically in the future.

Macromol doi: 10.3390/macromol3020017

Authors: Camila Ramão Contessa Gabriela Silveira da Rosa Caroline Costa Moraes Janaina Fernandes de Medeiros Burkert

The food industry produces an exorbitant amount of solid waste of petrochemical origin as a result of the increase in the development of new products. Natural polymers are an alternative to this theme; however, their development with adequate properties is a challenge. The union of different polymers in the synthesis of packaging is usually carried out to improve these properties. The combination of agar-agar and chitosan biopolymers show particular advantages through hydrogen bonds and electrostatic attraction between oppositely charged groups, presenting a promising source of studies for the synthesis of green packaging. When combined with natural extracts with active properties, these polymers allow an increase in the microbiological stability of foods associated with lower chemical preservative content and greater environmental sustainability.

Macromol doi: 10.3390/macromol3020016

Authors: Masatoshi Hasegawa Shunichi Horii

Heat-resistant polymers with an intense, visible photoluminescence (PL) functionality are presented. A polybenzoxazole (PBO) containing hexafluoroisopropylidene (HFIP) side groups exhibited an intense purple PL with a quantum yield, ΦPL, of 0.22 (22%), owing to the effectively disturbed concentration quenching (CQ) in the fluorophore units by the bulky HFIP side groups. The chain ends of a wholly cycloaliphatic polyimide (PI), derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 4,4′-methylenebis(cyclohexylamine) (MBCHA), were modified with conjugated monoamines. The PI derived from 2,3,6,7-naphthalenetetracarboxylic dianhydride (2,3,6,7-NTDA) and MBCHA exhibited a very high glass transition temperature (Tg = 376 °C) and purple fluorescence from the S1(π,π*) state. However, its ΦPL value was lower than expected. A pronounced effect of fluorophore dilution using CBDA on the PL enhancement was observed. This is closely related to the planar structure of the 2,3,6,7-NTDA-based diimide units. By contrast, the counterpart using an 2,3,6,7-NTDA isomer, 1,4,5,8-NTDA, was virtually non-fluorescent, despite its sufficient dilution using CBDA. The PI film obtained using 3,3″,4,4″-p-terphenyltetracarboxylic dianhydride (TPDA) with a non-coplanar structure and MBCHA exhibited an intense blue fluorescence spectrum (ΦPL = 0.26) peaking at 434 nm. The dilution approach using CBDA enhanced its fluorescence up to a high ΦPL value of 0.41. Even when TPDA was combined with an aromatic diamine, 2,2′-bis(trifluoromethyl)benzidine (TFMB), the intense blue fluorescence was observed without charge-transfer fluorescence. A semi-cycloaliphatic PI derived from TFMB and a novel cycloaliphatic tetracarboxylic dianhydride, which was obtained from a hydrogenated trimellitic anhydride derivative and 4,4′-biphenol, was used as another host polymer for 9,10-bis(4-aminophenyl)anthracene (BAPA). The BAPA-incorporating PI film resulted in a significant PL enhancement with a considerably high ΦPL of 0.48. This PI film also had a relatively high Tg (265 °C). A reactive dye, N,N′-bis[4-(4-amino-3-methylbenzyl)-2-methylphenyl]-3,4,9,10-perylenetetracarboxydiimide, was harnessed as a fluorescence probe to explore transamidation between polyimide precursors in solution.

Macromol doi: 10.3390/macromol3020015

Authors: Thea Serra Laura Anfossi Simone Cavalera Matteo Chiarello Fabio Di Nardo Valentina Testa Claudio Baggiani

The solid-phase polymerization synthesis (SPPS) represents one of the most innovative approaches to the preparation of nano-sized molecularly imprinted polymers. One of its main features consists of the use of a solid support on which the template molecule is covalently grafted. It implies that the imprinting process does not involve the target molecule as is, but, rather, a structural modification of it. It is known that the rationally designed mimic N-(4-chloro-1-hydroxy-2-naphthoylamido)-(L)-phenylalanine (CHNA-Phe) is able to generate, by bulk polymerization, imprinted materials capable of recognizing the mycotoxin Ochratoxin A (OTA). In this work, we wanted to verify whether the CHNA-Phe can be a useful mimic template in the SPPS technique. The binding isotherm were measured in the pH range of 4–8 and the binding affinities for CHNA-Phe and OTA were compared, showing that CHNA-Phe-imprinted nanoMIPs recognize, in buffered water, equally well OTA, and that the overall molecular recognition depends markedly from pH-related ionic interactions between the ligand and the binding site. There results confirm that in the SPPS method, it is possible and convenient to use as mimic templates a molecule whose three-dimensional structure is to some extent different from the target without substantial loss of selectivity or binding affinity.

Macromol doi: 10.3390/macromol3020014

Authors: Goshi Kuno Akikazu Matsumoto

Induced pluripotent stem cells (iPSCs) may develop into any form of cell and are being intensively investigated. The influence on iPSCs of nanostructures generated using two-dimensional colloidal arrays was examined in this study. Colloidal arrays were formed using the following procedure. First, core–shell colloids were adsorbed onto a glass substrate using a layer-by-layer method. Second, the colloids were immobilized via thermal fusion. Third, the surface of the colloids was modified by plasma treatment. By adjusting the number density of colloids, cultured iPSCs were easily detached from the substrate without manual cell scraping. In addition to planar culture, cell aggregation of iPSCs attached to the substrate was achieved by combining hydrophilic surface patterning on the colloidal array. Multilayered cell aggregates with approximately four layers were able be cultured. These findings imply that colloidal arrays might be an effective tool for controlling the strength of cell adhesion.

Macromol doi: 10.3390/macromol3020013

Authors: Tina Sabel-Grau

Understanding the formation processes of holographic gratings in polymers as a function of material composition and processing is important for the development of new materials for holography and its associated applications. Among the processing-related factors that affect grating formation in volume holographic recording material, pre-exposure, prebaking and dark storage, as well as the associated variations in layer thickness and composition, are usually underestimated. This study highlights the influence and interaction of these factors and shows that they should not be neglected. This is of particular importance for samples with a free surface. Here, one such epoxy-based free-surface material is investigated. To determine the influence of prebaking on the holographic grating formation, as well as on the achieved refractive index contrast, angular resolved analysis of volume holographic phase gratings is applied through point-by-point scanning of the local material response. Grating characteristics are determined by comparison with simulations based on rigorous coupled wave theory. Thus, the optimal dose for prebaking can be determined, as well as the optimal exposure time, depending on the dose. The influence of dark storage on the material response is investigated over a period of 12 weeks and shows a strong dependence on the deposited energy density.

Macromol doi: 10.3390/macromol3020012

Authors: Rafaela R. Ferreira Marilia C. Farina Anderson Maia Rondes F. S. Torin

This work evaluated the synergistic effect of citronella essential oil (Ct) and montmorillonite (MMT) (called hybrid compound) incorporated in Poly(lactic acid) (PLA) films at different concentrations (3, 10, 15, and 20 wt%). PLA films were characterized using X-ray diffraction, SEM, TGA, and DSC considering their mechanical properties and essential oil migration. XRD analysis showed the effective interaction between MMT and oil. Thermal analysis, SEM, and mechanical tests were essential to understand the saturation point of the PLA composites. Samples with 15% and 20% of Ct showed a crystallinity reduction of 0.5% compared to samples with 3% and 10% of Ct. PLA/MMT–Ct showed a reduction in tensile strength of the order of 16 and 24, correlated to 15% and 20% of the Ct content, respectively, compared to PLA/MMT–Ct3%. Migration tests showed fast oil delivery correlated with high oil concentration, as evidenced using the PLA/MMT–Ct20% sample results, which showed an estimated release of 50% in the first 150 h due to system saturation, and the remaining being released in the last 350 h. Therefore, the migration tests provide an effective Ct concentration range promising for application with active packaging due to the intrinsic antimicrobial properties of Ct.

Macromol doi: 10.3390/macromol3020011

Authors: Masatoshi Hasegawa Hiroki Sato Katsuhisa Hoshino Yasuhisa Arao Junichi Ishii

A cycloaliphatic tetracarboxylic dianhydride, octahydro-2,3,6,7-anthracenetetracarboxylic dianhydride (OHADA) was synthesized to obtain novel colorless polyimides (PIs). Herein, approaches for decolorizing an OHADA prototype and simplifying the entire process are described, and a plausible steric structure for OHADA is proposed. The polyaddition of OHADA and 2,2′-bis(trifluoromethyl)benzidine (TFMB) was unsuccessful; specifically, the reaction mixture remained inhomogeneous even after prolonged stirring. However, the modified one-pot process was applicable to the OHADA/TFMB system. The isolated PI powder form, as well as those for the other OHADA-based PIs, was highly soluble in numerous solvents and afforded a homogeneous and stable solution with a high solid content (20–30 wt%). Solution casting produced a colorless and ductile PI film with a very high glass transition temperature (Tg~300 °C). Furthermore, the OHADA/TFMB system exhibited remarkable thermal stability compared with those of the other related TFMB-derived semi-cycloaliphatic PIs. However, contrary to our expectations, this PI film did not exhibit a low linear coefficient of thermal expansion (CTE). This PI film also possessed excellent thermoplasticity, probably reflecting its peculiar steric structure. The use of an amide-containing diamine significantly enhanced the Tg (355 °C) and somewhat reduced the CTE (41.5 ppm K−1) while maintaining high optical transparency and excellent solubility.

Macromol doi: 10.3390/macromol3020010

Authors: Frédéric Dumur

The design of photoinitiators activable under low-light intensity is an active research field, supported by the recent energetic sobriety plans imposed by numerous countries in Europe. With an aim to simplify the composition of the photocurable resins, Type I photoinitiators are actively researched as these structures can act as monocomponent systems. In this field, a family of structures has been under-investigated at present, namely, glyoxylates. Besides, the different works carried out in three years have evidenced that glyoxylates and related structures can be versatile for the design of Type I photoinitiators. In this review, an overview of the different glyoxylates and related structures reported to date is provided.

Macromol doi: 10.3390/macromol3020009

Authors: Sabrina Bianchi Flavia Bartoli Cosimo Bruni Cristina Fernandez-Avila Laura Rodriguez-Turienzo Jorge Mellado-Carretero Daniele Spinelli Maria-Beatrice Coltelli

The recovery and recycling of textile waste is becoming urgent since textiles are generating more and more waste. In one year, about 92 million tons of textile waste are produced and the fashion industry accounts for 58 million tons of plastic waste per year. Several different synthetic fibres are used in textiles, thanks to their excellent processability and mechanical properties, but on the other hand, the difficulties linked to their end of life and the release of microplastics from them during washing is currently a cause of great concern. In this context, policy actions have been aimed at promoting recycling of waste and replacing fossil-based fibres with biobased fibres. The current review, considering both scientific papers published on international journals and web sources, considers the sorting of textiles and the possible recycling of polyesters, polyamides and acrylics. Nevertheless, the contamination and presence of mixed fibres in fabrics is another issue to face for recycling. Methodologies to solve the issue linked to the presence of elastane, present in the stretch fabrics, as well as the possibility of recycling textiles in the non-woven and composite sector are investigated. Moreover, chemical recycling and enzymatic recycling of fossil polymers are also considered. Thanks to the comprehensive scheme of this review, it is possible to deduce that, while the use of biobased materials should rapidly increase in textile applications, the perspective of recycling materials obtained from waste textile into durable and/or high-performance products seems the most promising.

Macromol doi: 10.3390/macromol3020008

Authors: Ana M. Díez-Pascual

Polymeric materials have recently attracted a lot of attention due to their potential applications in many fields, ranging from biomedicine, the food industry and environmental monitoring to electronic, energy storage and sensing devices. Their versatility, functionalization capability, chemical/physical stability, reusability, long shelf-life, as well as good mechanical and thermal properties, also make them idoneous candidates for use in forensic sciences, which deal with the investigation of crimes, finding relations between evidence and criminals. In particular, molecularly imprinted polymers (MIPs), designed based on the principle of generating template-specific polymeric cavities fitted to the target molecules in the presence of selected chemicals via non-covalent or covalent interactions, are highly suitable for forensic analysis. In addition, their combination with other compounds such as carbon nanomaterials can provide composites with improved properties to be used in the analysis of illicit drugs, doping substances, biological agents, toxins and so forth. In this article, recent applications of polymeric materials in the field of forensic analysis are discussed. The goal is to summarize their current uses and put forth a projection of their potential as promising alternatives for standard competitors.

Macromol doi: 10.3390/macromol3010007

Authors: Cindy Trinh Sandrine Hoppe Richard Lainé Dimitrios Meimaroglou

The study of the styrene–Ground Tire Rubber (GTR) graft radical polymerization is particularly challenging due to the complexity of the underlying kinetic mechanisms and nature of GTR. In this work, an experimental study on two scales (∼10 mL and ∼100 mL) and a machine learning (ML) modeling approach are combined to establish a quantitative relationship between operating conditions and styrene conversion. The two-scale experimental approach enables to verify the impact of upscaling on thermal and mixing effects that are particularly important in this heterogeneous system, as also evidenced in previous works. The adopted experimental setups are designed in view of multiple data production, while paying specific attention in data reliability by eliminating the uncertainty related to sampling for analyses. At the same time, all the potential sources of uncertainty, such as the mass loss along the different steps of the process and the precision of the experimental equipment, are also carefully identified and monitored. The experimental results on both scales validate previously observed effects of GTR, benzoyl peroxide initiator and temperature on styrene conversion but, at the same time, reveal the need of an efficient design of the experimental procedure in terms of mixing and of monitoring uncertainties. Subsequently, the most reliable experimental data (i.e., 69 data from the 10 mL system) are used for the screening of a series of diverse supervised-learning regression ML models and the optimization of the hyperparameters of the best-performing ones. These are gradient boosting, multilayer perceptrons and random forest with, respectively, a test R2 of 0.91 ± 0.04, 0.90 ± 0.04 and 0.89 ± 0.05. Finally, the effect of additional parameters, such as the scaling method, the number of folds and the random partitioning of data in the train/test splits, as well as the integration of the experimental uncertainties in the learning procedure, are exploited as means to improve the performance of the developed models.

Macromol doi: 10.3390/macromol3010006

Authors: Cecilia Zárate-Pérez Rodrigo Ramírez-Aguilar Edgar A. Franco-Urquiza Carlos Sánchez-Alvarado

This work is a collaborative effort between academia and industry to promote the development of new sustainable and profitable materials for manufacturing products. Incorporating wood flour particles (WF) in polypropylene (PP) grants environmental advantages in developing products that use renewable resources to manufacture PP/WF composites using the melt intercalation process. However, the interaction between a hydrophilic strengthening phase (wood flour) with a nonpolar polymer matrix (PP) is poor, resulting in deficient mechanical performance. This investigation details the use of graft and masterbatch coupling agents to evaluate their effects on mechanical parameters. The low compatibility between the constituents favors increasing the composites’ thermal properties because the reinforcing phase acts as a nucleating agent. PP showed typical mechanical behavior, with a marked necking and a wide deformation capacity of approximately 180%. The mechanical behavior of the PP/WF composites revealed an elastic region followed by a termination after their yield point, shortening the stress–strain curves and reducing their ductility at strain values of approximately 2–4%. Graft coupling agents have better intermolecular performance with PP than masterbatch coupling agents. The modulus of elasticity of the composites increased to around 82% relative to PP. Processing methods influenced the thermal properties of the composites. The melt-blending process promoted molecular orientation, while injection molding erased the thermomechanical history of the extruded pellets. The melting temperature was similar in the composites, so there was no evidence of thermal degradation. The results showed that the coupling agents favor the crystallinity of the PP over tensile strength. SEM observations showed insufficient adhesion between the WF and PP, which promotes a reduction in stress transfer during tensile testing. The WF particles act as fillers that increase the stiffness and reduce the ductility of composites.

Macromol doi: 10.3390/macromol3010005

Authors: Xiao-Jun Ma Qi-Yu Ye Shao-Jie Zheng Ji-Jiang Hu Zhen Yao

In this work, nylon 6 (PA6) and cationic dyeable polyester (CDP) modified with benzenesulfonate groups were reactively blended in a twin-screw extruder. The well-mixed CDP/PA6 blends were re-molten and statically kept for various amounts of time. The morphology evolution caused by phase separation was observed by a scanning electron microscope (SEM) and an atomic force microscopy-infrared (AFM-IR) technique. In the absence of shear force, the homogeneously mixed blends were found to separate rapidly into two phases because of the poor miscibility between polyester and polyamide. In the early stage, the dispersed phase was small in size and irregular in shape. With prolongation of the phase separation time, the dispersed phase turned into larger and spherical particles to minimize the interface between phases. The phase separation process typically lasted 2 to 7 min. This means that the effects of phase separation on the morphology of the blends cannot be ignored in injection molding, compression molding, or other processing processes short of shear force. The effects of the ratio between polyester and polyamide, the benzenesulfonate content, and the molecular weight of polymers on phase separation behavior were investigated.

Macromol doi: 10.3390/macromol3010004

Authors: Danielle M. Beaupre Alexander K. Goroncy Richard G. Weiss

A simple, efficient procedure has been employed to effect intra- and inter-chain crosslinking of two commercially available thiolated poly(dimethylsiloxane) copolymers (T-PDMS) with 4–6% or 13–17% of mercaptopropyl side-chains. The thiol functional groups were converted to disulfides (D-PDMS) in chloroform solutions of I2. Importantly, the conditions employed avoid over-oxidation to other types of sulfur-containing species, and the concentration of T-PDMS during the crosslinking reaction dictated the rheological properties and liquid or solid nature of the D-PDMS. The procedure for obtaining the crosslinked copolymers is simpler than other approaches in the literature used to crosslink polysiloxane backbones and to modulate their properties. By changing the concentration of T-PDMS during the treatment with I2, the degree of intra- and inter-chain crosslinking can be controlled (as assessed qualitatively by the solid or liquid nature of the products and their viscoelastic properties). For each of the T-PDMS materials, there is a concentration threshold, above which products are solids, and below which they are oils. Liquid and solid materials were characterized using 1H and 13C solution-state and 13C solid-state NMR spectroscopy, respectively. They indicate greater than 90% conversion of thiols to disulfides in the presence of excess I2. The rheological behavior of the liquid products, solvent swelling ability of solid products, and the thermal stability of the reactants and products are described. Furthermore, the solid products exhibit some of the highest swelling values reported in the literature for poly(dimethylsiloxane) (PDMS) materials. As assessed by thermal gravimetric analyses, the disulfide-crosslinked materials are more stable thermally than the corresponding thiols.

Macromol doi: 10.3390/macromol3010003

Authors: Macromol Editorial Office Macromol Editorial Office

High-quality academic publishing is built on rigorous peer review [...]

Macromol doi: 10.3390/macromol3010002

Authors: Ana M. Díez-Pascual

In 1920, Hermann Staudinger discovered that macromolecules consist of long chains of covalently linked building blocks and subsequently published the first paper on polymerization [...]

Macromol doi: 10.3390/macromol3010001

Authors: Johan Stanley Athira John Klementina Pušnik Črešnar Lidija Fras Zemljič Dimitra A. Lambropoulou Dimitrios N. Bikiaris

Active packaging has played a significant role in consumers’ health and green environment over the years. Synthetic polymers, such as poly(ethylene terephthalate) (PET), polyethylene (PE), polypropylene (PP), polystyrene, poly(vinyl chloride) (PVC), polycarbonate (PC), poly(lactic acid) (PLA), etc., and naturally derived ones, such as cellulose, starch, chitosan, etc., are extensively used as packaging materials due to their broad range of desired properties (transparence, processability, gas barrier properties, mechanical strength, etc.). In recent years, the food packaging field has been challenged to deliver food products free from microbes that cause health hazards. However, most of the used polymers lack such properties. Owing to this, active agents such as antimicrobial agents and antioxidants have been broadly used as potential additives in food packaging substrates, to increase the shelf life, the quality and the safety of food products. Both synthetic active agents, such as Ag, Cu, ZnO, TiO2, nanoclays, and natural active agents, such as essential oils, catechin, curcumin, tannin, gallic acid, etc., exhibit a broad spectrum of antimicrobial and antioxidant effects, while restricting the growth of harmful microbes. Various bulk processing techniques have been developed over the years to produce appropriate food packaging products and to add active agents on polymer matrices or on their surface. Among these techniques, extrusion molding is the most used method for mass production of food packaging with incorporated active agents into polymer substrates, while injection molding, thermoforming, blow molding, electrospinning, etc., are used to a lower extent. This review intends to study the antimicrobial and antioxidant effects of various active agents incorporated into polymeric substrates and their bulk processing technologies involved in the field of food packaging.

Macromol doi: 10.3390/macromol2040037

Authors: J. Esquena-Moret

The present paper reviews the self-aggregation, gel-forming and adsorption properties of xyloglucan (XG), and its main applications as a medical device for wound dressings, mucosal protection and ocular lubrication, as well as its uses as an excipient. XG is a branched polysaccharide composed of a central backbone of D-glucose units linked by β(1→4)-glycosidic bonds, decorated with D-xylose units through α(1→6) glycosidic bonds, and with some D-galactose units anchored to these D-xylose units via β(1→2) bonds. XG forms self-aggregates with a hierarchically ordered morphology in aqueous solutions, leading to the formation of nanofibers. Consequently, XG is a hydrogel-forming polymer able to retain large amounts of water. Inside the human digestive tract, XG is enzymatically degalactosylated, but the backbone with xylose side chains remains stable until excretion. Degalactosylated XG undergoes a fully reversible sol–gel transition, forming hydrogels between upper and lower critical temperatures. XG adsorbs on intestinal mucosa and creates a diffusion barrier that reduces permeability and also prevents bacterial infections by reducing their infiltration. Therefore, orally administered XG is considered a mucosa protectant.

Macromol doi: 10.3390/macromol2040036

Authors: Rami Rouhana Markus Stommel Michael Stanko Markus Muth

A patterned carbon film was produced from Linear Low-Density Polyethylene (LLDPE) by the implementation of a novel method named Chemical Masking Perforation (CMP). The following paper describes this procedure, starting with the sulfonation of the precursor polymer LLDPE with Chlorosulphonic acid to stabilize the material, followed by Fourier-transform infrared spectroscopy (FTIR) evaluation to compare the atomic bonds from the stabilized film as well as from the masked sections of the film. To finalize, the cross-linked film was carbonized in an oven at 950 °C. The outcome of this process was a carbon film with a thickness similar to a carbon fiber diameter of 8 µm with controllable size and distribution.

Macromol doi: 10.3390/macromol2040035

Authors: Rauf Mahmudzade Dilip Depan

Wearable technologies can contribute to the early and accurate detection of chronic diseases which can be achieved by the integration of biosensors into wearable technologies. However, the challenges associated with the performance of current electrode materials—i.e., flexibility, conductivity, and mechanical stability, made from conducting polymers are preventing their widespread usage. Herein, we report a freestanding and flexible electrode synthesized from polyaniline (PANI) and graphene nanoscrolls (GNS). The PANI-GNS nanohybrid membranes were synthesized via chemical oxidative polymerization and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), nanoindentation (NI), and four-point probe techniques. FTIR results showed an increase in conjugation length of the PANI after the addition of GNS into the mixture which can be indicative of an enhancement of electrical properties. Nanoindentation studies showed an elastic modulus and hardness of 2.6 GPa and 0.17 GPa, respectively, for PANI-GNS-5 nanocomposite, compared to 1.9 GPa and 0.08 GPa, for pure PANI. This was later confirmed by the four-point probe technique as the addition of GNS increased the conductivity of electrodes up to 9 S/cm at a 5% weight ratio. Moreover, SEM results of the PANI-GNS showed an open porous morphology of the polymer matrix in comparison with pure PANI samples which would readily translate into higher amounts of enzyme immobilization on the surface.

Macromol doi: 10.3390/macromol2040034

Authors: Sérgio D. Almeida Jorge C. Silva João P. M. R. Borges M. Carmo Lança

Damage to bone tissue is a common health issue that tends to increase in severity with age and other underlying conditions. To take advantage of the piezoelectric effect on bone remodulation, piezoelectric materials can be used to fill patients bone defects. Polyvinylidene fluoride (PVDF) and barium titanate (BaTiO3) are both well-known polymeric and ceramic biomaterials, respectively, as well as piezoelectric at room temperature. To mimic the extracellular matrix, PVDF membranes were produced by electrospinning onto a rotating drum to promote the alignment of fibers and micro- and nano-sized tetragonal BaTiO3 particles were embedded into these membranes to try to enhance the piezoelectric response and, therefore, bioactivity. After defining the best deposition parameters to produce pure PVDF membranes, the same parameters were carried over for the embedded membranes and both were characterized, revealing that the proposed method for obtaining β-phase PVDF (the polymer phase with highest piezoelectric coefficient) through electrospinning is viable, producing fibers with coherent diameters and alignment. The presence of barium titanate conferred bioactivity to the membranes and caused a decrease in fibers’ diameter and in superficial charge density.

Macromol doi: 10.3390/macromol2040033

Authors: Eldor Urinov Stefan Hanstein Anke Weidenkaff

Application of thermoplastic fiber-reinforced lightweight composite materials provides a wide range of advantages that are of particular importance for the mobility sector. UD tapes composed of unidirectionally (UD) oriented inorganic fibers embedded in a thermoplastic matrix represent light-weight materials with high tensile strength. This publication addresses recycling aspects of novel UD tape made of a combination of basalt fibers and different PLA (polylactic acid) formulations. The kinetics of enzyme-based separation of polymer from the fiber were investigated. Different types of UD tapes with a thickness of 270–290 µm reinforced with basalt fiber weight ratios ranging between 51 and 63% were incubated at 37 °C in buffer solution (pH 7.4) containing proteinase K. The influence of enzyme concentration, tape weight per incubation tube, proteinase K activators, and tape types on the rate of enzymatic decomposition was investigated. Enzyme activity was measured by analyzing lactate concentration with lactate dehydrogenase and by measuring weight loss of the composite material. The rate of lactate release increased in the first 30 min of incubation and remained stable for at least 90 min. Weight loss of 4% within 4 h was achieved for a tape with 56% (w/w) fiber content. For a sample with a surface area of 3 cm2 in a buffer volume of 10 mL, the rate of lactate release as a function of enzyme concentration reached saturation at 300 µg enzyme/mL. With this enzyme concentration, the rate of lactate release increased in a linear manner for tape surface areas between 1 and 5 cm2. Four tapes with different PLA types were treated with the enzyme for 17 h. Weight loss ranged between 7 and 24%. Urea at a concentration of 0.5% (w/v) increased lactate release by a factor of 9. Pretreatment of tapes in alkaline medium before enzymatic degradation increased weight loss to 14% compared to 5% without pretreatment. It is concluded that enzymatic PLA hydrolysis from UD tapes is a promising technology for the release of basalt fibers after alkaline pretreatment or for the final cleaning of basalt fibers.

Macromol doi: 10.3390/macromol2040032

Authors: Vito Gigante Laura Aliotta Maria-Beatrice Coltelli Andrea Lazzeri

Coupling recycling processes with increased use of bio-derived and environmentally friendly materials, with the aim of approaching (or overcoming) the mechanical properties of petroleum-derived plastics, is a path that research is pursuing in small but important steps. It is in this stream that this paper wants to fit in developing recycled poly(lactic acid) (R-PLA)/recycled polycarbonate (R-PC) blends obtained from thermoforming processing scraps and reinforcing them with cellulosic-derived fibers, having three different aspect ratios. The aim is to understand the mechanical properties of “second life” materials, their adherence to some micromechanical predictive models and the reinforcement capacity of these natural fibers in relation to their dimensions. Moreover, a compatibilizing system, based on Triacetin (TA) and Tetrabutylammonium Tetraphenylborate (TBATPB), has been added during the extrusion to investigate if a reactive process among R-PLA/R-PC and cellulosic fibers can be achieved.

Macromol doi: 10.3390/macromol2040031

Authors: Ilaria D’Auria Zeinab Saki Ming Liu Wen-Hua Sun Claudio Pellecchia

Copolymerization of ethylene with polar vinyl monomers to yield functionalized and possibly easier recyclable polyolefins is challenging and it is currently being pursued mainly using expensive Pd-based catalysts. Herein, the copolymerization of ethylene and methyl acrylate (MA) is achieved by the dibenzocycloheptyl-substituted aryliminopyridyl Ni(II) complexes, affording copolymers with selectively in-chain incorporated MA units as well as both in-chain and end-of-chain inserted MA units depending on the catalyst structure and the reaction conditions

Macromol doi: 10.3390/macromol2030030

Authors: Dimakatso Makwakwa Mpho Phillip Motloung Vincent Ojijo Jayita Bandyopadhyay Suprakas Sinha Ray

The technology of 4DP utilizes shape memory materials (SMMs). Among the SMMs, SMP is the material that has potential and is ideal for this technology. However, due to their restrictions, fillers are incorporated to produce a novel shape memory polymer composite (SMPC). The objective of the present work was to investigate how the modification of PLA via the incorporation of boehmite alumina and thermochromic dye, and the use of 3DP on polyester fabric to make smart material textiles (SMT), influenced the shape-memory properties of printed objects. SMPCs with 3 wt% BA particles were prepared by means of the fused deposition modelling (FDM) process, with heat used as an actuation. It was demonstrated that sample thickness and the method of PLA modification affected the shape recovery of 3D-printed objects. All neat PLA samples recovered their angle fully for all thicknesses, while modified PLA incorporated with BA particles and dye recovered its initial angle fully at 1 mm thickness and showed less recovery for 1.5- and 2 mm-thicknesses. The 1 mm-thick sample was then chosen for printing onto the textile material for all samples. When printed onto the fabric, the neat PLA and SMPCs recovered their initial shapes fully, while samples with the dye added into the PLA and SMPC did not recover their initial shape fully due to the presence of the dye, which hindered the movement of the polymer chains. SEM revealed good layer bonding for the SMPCs compared to the neat PLA, which led to improved mechanical properties. The thermal stability of PLA was improved by the BA particles; furthermore, the dye and BA particles nucleated the crystallization of PLA, resulting in an enhanced storage modulus. Overall, a biodegradable 3D-printed object of 1 mm in thickness with improved thermal and mechanical properties was produced, with and without the use of the textile.

Macromol doi: 10.3390/macromol2030029

Authors: Alexandra M. Smink Bryan Ceballos Taco Koster Samuel Rodriquez Michael Alexander Jonathan R. T. Lakey Paul de Vos

Subcutaneous polymer scaffolds have shown potential for creating an optimal transplantation site in cellular replacement therapy, e.g., when transplanting insulin-producing cells to cure type 1 diabetes. Imperative for these scaffolds is a high degree of vascularization to guarantee long-term functional cellular survival. In this study, the effect of the nitric oxide (NO) donor S-nitroso-N-acetyl-dl-penicillamine (SNAP) on the vascularization degree of a subcutaneous poly(d,l-lactide-co-ε-caprolactone) (PDLLCL) scaffold was investigated. To this end, scaffolds were implanted under the skin of C57BL/6 mice. Each mouse received a control scaffold and a scaffold containing SNAP. At day 7, 14, and 28, the oxygen percentage within the scaffolds was measured and at day 28, the vascularization degree was determined with lectin infusion and gene expression analysis. We measured lower oxygen percentages within the scaffolds containing the NO-donor up to day 14 compared to the control scaffolds, but no differences were found at day 28. Although blood vessels in the scaffolds were well perfused, no differences between the groups were found in the lectin staining and gene expression of vascular markers, such as CD31, CD105, and VEGFa. To conclude, in this biomaterial setting, addition of a NO-donor did not improve the vascularization degree of the subcutaneous scaffold.

Macromol doi: 10.3390/macromol2030028

Authors: Cesar A. Barbero María V. Martínez Diego F. Acevedo María A. Molina Claudia R. Rivarola

Cross-linked gels are synthesized by homo- and copolymerization of functionalized acrylamides. The gels swell in aqueous solution, and some of them (e.g., poly(N-isopropylacrylamide (PNIPAM)) also in organic solvents of low polarity (e.g., dichloromethane), making the gels amphiphilic materials. Nanocomposites can be made by dispersing nanoparticles (metallic, graphene, nanotubes, and conducting polymers) inside the gels. Additionally, true semi-interpenetrated networks of polyaniline (PANI) inside PNIPAM gels can be prepared by swelling the gel in true solutions of PANI in NMP. PNIPAM-based nanocomposites show a lower critical solution temperature (LCST) transition of the gel matrix, which can be reached by thermal heating or absorption of electromagnetic radiation (light, microwaves, radiofrequency) in the conductive nanomaterials. The characteristic properties (swelling degree and rate, LCST, solute partition, mass transport, hydrophilicity, biocompatibility) can be tuned by changing the functional groups in the copolymers and/or the other components in the nanocomposite. Mass transport and mechanical properties can be adjusted by forming materials with macro- (nanoporous and macroporous), micro- (microgels, thin films, Pickering emulsions), or nano- (nanogels, stabilized nanoparticles) sized features. The material properties are used to produce technological applications: sensors, actuators, controlled release, biological cell scaffolds and surfaces, antimicrobial, carriers of bioactive substances, and matrixes to immobilize enzymes and yeast cells.

Macromol doi: 10.3390/macromol2030027

Authors: Magda Lorena Arciniegas Vaca Jimena S. Gonzalez Cristina E. Hoppe

Poly(ethylene glycol) (PEG)-based soft elastomers, bearing tertiary amine and hydroxyl groups, were synthesized in bulk from the epoxy–amine reaction between poly(ethylene glycol) diglycidyl ether (PEGDE) and a poly(etherdiamine), Jeffamine ED600. High gel fractions (≥0.95) and low glass transition temperatures (Tg ≈ −50 °C) were attained after complete curing of the systems in bulk. The amphiphilicity of the network allowed the swelling of the materials in both aqueous solutions and a variety of organic solvents. Magnetic nanocomposites were synthesized by in situ coprecipitation of magnetic nanoparticles (MNPs) in the elastomeric matrix. The obtained materials were processed by cryogenic milling to obtain powders that were tested as potential magnetic adsorbents and that showed a fast and strong response to the action of a permanent magnet. These materials showed removal rates of at least 50% in 10 min when used in the adsorption of Cu+2 ions from an aqueous solution, making them interesting candidates for the design of magnetically separable metal ion adsorbents.

Macromol doi: 10.3390/macromol2030026

Authors: Dimitrios G. Trikkaliotis Nina Maria Ainali Athanasia K. Tolkou Athanasios C. Mitropoulos Dimitra A. Lambropoulou Dimitrios N. Bikiaris George Z. Kyzas

Through epistemic efforts in water remediation, numerous sorbents have emerged as either low-cost or more expensive. This review article describes the properties, functions and modifications of cost-effective sorbents based on chitosan and poly(vinyl alcohol) blends for aqueous solutions treatment from heavy metals. Interesting synthesis routes have been reported for the production of membranes, beads, foams and mats, while the kinetic and thermodynamic studies provide spherical knowledge of the system. Tables with the adsorbent’s capacity and enthalpy change are included, while indicative images from the synthesis and characterization techniques of the adsorbents are presented.

Macromol doi: 10.3390/macromol2030025

Authors: Traian Zaharescu Tunde Borbath Marius Mariș Istvan Borbath Mihaela Mariș

The stability of polymer materials is essentially determined by the molecular structure and the presence of additives and impurities. When a polymer substrate is subjected to vigorous damage by an energetic treatment, the molecular scission generates fragments, which may be oxidized by the diffused oxygen. The traces of oxide catalysts that may be accidentally incorporated into the polymer materials initiate a faster oxidation that influences the material durability. This study presents the behavior of poly (ε-caprolactone) (PCL) loaded with 2 wt% PbZrO3 previously doped with foreign atoms (Cr, Nd, Mg, Mn, Ti) at the concentration of 0.1 mol%. The investigation procedure, chemiluminescence, reveals the acceleration of the degradation of PCL. The contribution of the metallic traces existing in the structure of PbTiO3 powder is characterized by the activation energies (Ea) involved in the propagation of oxidation. The free radicals are involved in a faster oxidation, when the polymer substrate is heated at superior rates. The comparison of the oxidation levels at the extended period of heating and irradiation indicates the sustained activities of metallic traces acting in oxide powder fillers, especially at temperatures exceeding 150 °C. The essential considerations on material strength against oxidation are presented.

Macromol doi: 10.3390/macromol2030024

Authors: Guadalupe Gabriel Flores-Rojas Felipe López-Saucedo Ricardo Vera-Graziano Eduardo Mendizabal Emilio Bucio

Magnetic nanoparticles (MNPs) represent an advanced tool in the medical field because they can be modified according to biomedical approaches and guided by an external magnetic field in the human body. The first objective of this review is to exemplify some promising applications in the medical field, including smart drug-delivery systems, therapies against cancer cells, radiotherapy, improvements in diagnostics using magnetic resonance imaging (MRI), and tissue engineering. Complementarily, the second objective is to illustrate the mechanisms of action and theoretical foundations related to magnetoresponsive materials.

Macromol doi: 10.3390/macromol2030023

Authors: Rasoul Niknam Mohammad Reza Soudi Mohammad Mousavi

The effects of treating two biopolymers (Trigonella foenum—graceum galactomannan and xanthan gum mixtures) with microwaves and ultrasound on the rheological aspects of O/W emulsions were investigated. The data obtained from steady shear flow were fitted with various models and the best were chosen due to the values of R2 and RMSE. The oscillatory shear rheology data demonstrated that the emulsions not treated with microwaves or ultrasound had viscous-like behavior and treated samples demonstrated weak gel behavior. The values obtained for various rheological parameters (especially apparent viscosity, storage modulus and loss modulus) indicated that fenugreek galactomannan had more impact on the rheological aspects of emulsions in comparison with xanthan gum. In addition, the synergistic interaction between two biopolymers, particularly in samples treated with ultrasound, resulted in better rheological aspects which could be affiliated with the strong bonds between the hydrocolloids. By treating the samples with microwaves and ultrasound, the emulsion stability values of the samples (especially those with a high ratio of galactomannan) significantly increased, which might be connected with various parameters, especially viscosity.

Macromol doi: 10.3390/macromol2030022

Authors: Huiyang Jin Zhengke Wang

Chitosan, a natural polysaccharide, has been widely used as a biomaterial, especially for hemostasis. However, hemostatic materials processed from pure chitosan have limited hemostatic effect and are extremely unstable in some cases; chemical modification is therefore needed to improve the hemostatic properties of chitosan. Through chemical reactions with hydroxyl and amino groups in chitosan macromolecules, such as alkylation, carboxylation, quaternization, etc., different groups can be introduced into the repeating units. Moreover, the introduction of different substituents can endow chitosan with more functions. For example, the introduction of long alkyl chains can improve its hydrophobic property, and greatly improve its hemostatic property. However, there is still no review of alkylated chitosan for hemostasis. Therefore, we introduce in detail several methods (direct alkylation, reductive alkylation and acylation reaction) for preparing alkylated chitosan and its applications for hemostasis.

Macromol doi: 10.3390/macromol2030021

Authors: Stylianos Exarhopoulos Athanasios Goulas Georgia Dimitreli

Kefiran, which was isolated from kefir grains, was used for the fabrication of cryogel-films in the presence of plasticizers, such as glycerol and sorbitol. Varying concentration ratios of the exopolysaccharide/plasticizer system were employed in the process of the cryogel-film formulation and their effect on the physical (film thickness, moisture content, and solubility) and the mechanical (tensile strength and elongation at break) properties of the films was monitored. Kefiran-film vapor adsorption isotherms were calculated, and a thermal analysis of the samples was also performed. The structural characteristics of the cryogel-films were observed using confocal laser scanning microscopy. The cryo-treatment, alongside the plasticizer addition, affected the physical and mechanical properties of the kefiran films, as well as their morphology. Increasing kefiran concentration resulted in increasing the film thickness, the moisture content, and the tensile strength, while decreased their solubility and their elongation at break. Kefiran-film adsorption isotherms were affected by the cryo-treatment, the kefiran concentration, and the plasticizer use and concentration. The thermal analysis of the kefiran films showed thermal stability. The presence of the plasticizers and their increment concentration resulted in decreasing the glass transition and the melting temperatures. The cryo-treatment and the presence of plasticizers resulted in the films appearing smoother. Glycerol proved to affect more than the sorbitol–water vapor adsorption and the morphology of kefiran films.

Macromol doi: 10.3390/macromol2030020

Authors: Fahrunnida Puspa Restu Sayekti Colin Robert Bambang Retnoaji Parvez Alam

This paper focusses on the morphological and viscoelastic properties of the cicada tymbal from the species Dundubia rufivena. Morphological details were determined by scanning electron and fluorescence microscopy, while the viscoelastic properties were determined by dynamic mechanical thermal analysis, and further supported by differential scanning calorimetry. We find that water evaporation from the tymbal begins at 71.1 °C and the glass transition for the tymbal, which is a chitin–resilin composite, is on average 150 °C, though there is considerable heterogeneity in the material of the tymbal, as indicated by the half height peak width of the tymbal (35.3 °C) and the shoulder peak indicative of a second phase and hence glass transition at on average, 168 °C. This second phase is assumed to reflect the effects of large-scale molecular pinning and restructuring at resilin–chitin interfaces (possibly via specific binding domains). In addition, we elucidate that the predominantly resilin regions of the tymbal of Dundubia rufivena is reinforced by a polygonal mesh of chitin, a morphological feature that has not been described in any previous research on the cicada tymbal. We provide evidence for nonlinear elasticity in the tymbal by comparing the storage modulus of the tymbal at different frequencies and loading amplitudes.

Macromol doi: 10.3390/macromol2030019

Authors: Raminder Kaur Pooja Singh Surya Tanwar Gunjan Varshney Sarla Yadav

Among numerous synthetic macromolecules, polyurethane in its different forms has proven its sheer dominance and established a reputation as a reliable and trusted material due to its proficiency in terms of superior properties, which include: high mechanical strength and abrasion resistance, good durability, good adhesion, good thermal stability, excellent chemical and weathering resistance. Synthetic polyurethane materials are non-biodegradable, poisonous, and use petrochemical-based raw materials, which are now depleting, leading to a surge in polyurethane production costs. Bio-based polyurethanes (PU) have been synthesized by researchers in recent decades and have mostly overtaken petrochemical-based PU in terms of challenges such as solid pollution, economic effectiveness, and availability of raw materials. Enormous kinds of available bio-renewable sources as predecessors for the production of polyols and isocyanates have been explored for the development of “greener” PU materials; these bio-based polyurethanes have significant potential to be used as future PU products, with a partial or total replacement of petroleum-based polyurethanes, due to increasing concern about the environment, their relatively low cost and biodegradability. This critical review concentrates on the possibilities of renewable sources to be used for polyurethane production and gives a clear perspective on the journey, utilization, and recent advancements in the field of different bio-based polyurethane polymers that have arisen over the last decade.

Macromol doi: 10.3390/macromol2030018

Authors: Moises Bustamante-Torres Belén Arcentales-Vera Jocelyne Estrella-Nuñez Heidi Yánez-Vega Emilio Bucio

Microorganisms have developed a resistance against some of the most conventional antibiotics. These microorganisms can be self-assembled, forming a microbial biofilm. A microbial biofilm formation is an inherent event on almost any surface, causing countless side effects on human health and the environment. Therefore, multiple scientific proposals have been developed based on renewable sources such as natural polymers. Natural polymers or biopolymers include cellulose, chitosan, starch, collagen, gelatin, hyaluronic acid, alginates, fibrin, and pectin, which are widely found in nature. The biopolymers have displayed many interesting properties, including biocompatibility and biodegradability. Nonetheless, these materials usually have no antimicrobial properties (except for the chitosan) by themselves. Therefore, antimicrobial agents have been incorporated into the natural polymeric matrix, providing an antimicrobial property to the biocomposite. Biocomposites consist of two different materials (one of natural origin) studied as biocompatible and biodegradable drug carriers of antimicrobial agents. In addition, due to the incorporation of antimicrobial agents, biocomposites can inhibit biofilm formation and bacteria proliferation on many surfaces. This review describes this using natural polymers as a platform of antimicrobial agents to form a biocomposite to eliminate or reduce biofilm formation on different surfaces.

Macromol doi: 10.3390/macromol2030017

Authors: Blanca Maria Lekube Christoph Burgstaller

Non-woven materials feature unique properties that allow them to be used in different applications, such as the automotive sector that is increasingly seeking lightweight and sustainable materials. The aim of this work was to investigate the influence of reinforcement type and porosity on the properties of commingled, partially compacted composites based on polypropylene (PP) and polylactic acid (PLA). Furthermore, a model was applied to predict the properties of such composites, i.e., the elastic modulus, to aid materials development. It was found that high properties could be achieved using flax as reinforcement for partially compacted fleece biocomposites. Porosity is an important factor influencing these types of composites and was influenced by the compaction grade achieved as a result of stacking different numbers of layers during the consolidation of the composites. The modeling of the elastic modulus was found to be adequate for both PP-flax and PLA-flax composites for porosities under 20 vol.%.

Macromol doi: 10.3390/macromol2020016

Authors: Julie Meimoun Audrey Favrelle-Huret Julien De Winter Philippe Zinck

Organocatalysis for polymer chemistry has become a subject of significant interest in the last two decades. In this contribution, we have studied the evolution of the microstructure of poly(L-lactide) in solution in toluene at 105 °C in the presence of various organocatalysts. Weak bases such as triethylamine and DMAP (4-dimethylaminopyridine) lead to a low extent of epimerization and a chain scission reaction. The DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) amidine induces in turn important extents of both epimerization (up to 37% D-stereoisomer formation) and chain scission. This has been tentatively attributed to a nucleophilic mechanism. Cinchona alkaloids lead to only a modest amount of epimerization. Phosphazene bases are in turn rather active, especially for high catalytic loadings (>1 mol %). The chain scission observed in this case is proposed to occur via a base-catalyzed hydrolysis mechanism. Finally, it is shown that combining an organic base with an acid can lead to a synergistic effect regarding notably the chain scission reaction.

Macromol doi: 10.3390/macromol2020015

Authors: Xiaosong Ding Jian Wu Yonggang Wang Bo Cui Shuang An Benlong Su Youshan Wang

Due to the hydrodynamic pressure effect, the bearing capacity of the oil film on the surface of a textured friction pair is greater than that of a smooth surface. In this paper, the effects of PTFE surface texture parameters (shape, depth, width, and area ratio) on the oil film bearing capacity and leakage of the sealing system under lubrication are studied using the FLURNT simulation. It is found in this present study that greater texture depths do not necessarily lead to better sealing performance. When the texture depth exceeds a certain level, a reverse flow occurs at the bottom of the texture, thereby weakening the hydrodynamic pressure effect. An optimal texture depth of 5–10 μm maximizes the oil film bearing capacity. Within a certain range, the oil film bearing capacity increases along with texture widths. In addition, leakage of the rectangular texture rises significantly with growing texture widths. Larger texture area ratios result in higher leakage, but the bearing capacity first rises and then falls with an increase in the area ratio, with a maximum value of 70–80%. Considering the influence of texture parameters on oil film bearing capacity and leakage, selecting the most appropriate texture parameters for surface texture treatment optimizes the performance of the sealing system. The findings of this paper provide a theoretical basis for improving the sealing performance of high-end aviation equipment using texture treatment, thereby enabling the application of surface texture technology to improve the tribological properties of materials.

Macromol doi: 10.3390/macromol2020014

Authors: Syed Muhammad Imran Gwang-Myeong Go Manwar Hussain Mamdouh A. Al-Harthi

Thermoplastic polyurethane (TPU) is a widely used polymer for a variety of pressure sensing applications because of its softness and shape memory. This work reports the synthesis of novel TPU-based three-dimensional structured (3D) pressure-sensitive composites via the melt mixing method. Poly-methyl methacrylate (PMMA) microbeads of different sizes (5, 10, and 20 µm) were first coated with multi-walled carbon nanotubes (MWCNT) and then incorporated into the TPU matrix for achieving an early electro conductive percolation threshold compared to without PMMA beads. The addition of MWCNT coated PMMA beads reduced the TPU insulated areas by creating a 3D conductive network that finally reflected the early percolation threshold during external pressure. Raman microscopy and XRD results confirmed the MWCNT coated nicely on the surface of PMMA beads. The pressure sensitivity results also confirmed the decrease in resistance of the composites with the increase in the applied external pressure. Composites with 10 µm PMMA bead size showed the most linear responses to the decrease in resistance with increasing pressure and showed a higher strain gauge factor value (3.15) as compared to other composites, which had values of 2.78 and 2.42 for 20 and 5 µm, respectively. Microstructure analysis of the composites by SEM, capacitance, permeability, and thermal conductivity measurements was also investigated to support the above evidence. The results support the suitability of this novel composite as a potential candidate for pressure sensing applications.

Macromol doi: 10.3390/macromol2020013

Authors: Periklis Didaskalou Martha Kafetzi Stergios Pispas

In this work, the synthesis and solution self-assembly of partially fluorinated cationic polyelectrolytes based on post-polymerization-modified poly(2-(dimethylamino) ethyl methacrylate), incorporating hydrophobic fluorinated groups along the polymer chain, is reported. The post-polymerization modification aims to establish amphiphilic characteristics and strong polyelectrolyte properties to the polymer. Therefore, the self-organization characteristics in aqueous media are expected to be affected. The poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) homopolymer precursor is synthesized using RAFT polymerization. A quaternization reaction on the amine side groups using heptadecafluoro-10-iododecane results in the poly((2-dimethylamino) ethyl methacrylate-co-quaternized heptadecafluoro-10-iododecane (2-dimethylamino) ethyl methacrylate) (PQFD) amphiphilic statistical copolymers. We intentionally study statistical copolymers in our research of DMAEMA-based polyelectrolytes as there are not many studies about such materials. We have also chosen the incorporation of highly hydrophobic perfluorinated groups to study the changes in the solution properties of the initial hydrophilic homopolymer. The successful synthesis is supported by size-exclusion chromatography (SEC), 1H-NMR, and FTIR experiments. The self-assembly of the copolymers in aqueous solutions along with the dependence of the properties of the resulting aggregates on the pH, temperature, and ionic strength of the solution are studied using light scattering methods (DLS, ELS) and fluorescence spectroscopy (FS). The structural characteristics of the aggregates depend on composition, solution preparation protocol and solution pH, and temperature.

Macromol doi: 10.3390/macromol2020012

Authors: Nikolay G. Vladimirov Ivan Gitsov

This study reports the first attempt to employ a potassium–graphite intercalation compound (KC24) as an initiator for the one-pot synthesis of a multi-block copolymer. The results obtained show that KC24 successfully initiated the copolymerization, leading to a copolymer consisting of poly(styrene), poly(methyl methacrylate) and poly(ethylene oxide) blocks. When all three comonomers were introduced simultaneously or in a specific sequence, the resulting copolymers had molecular masses in the range between 170,000 Da and 280,000 Da. Their composition was investigated by size-exclusion chromatography with triple detection (dRI/UV/IR) and 1H-NMR. The analyses indicated that all copolymers were enriched in methyl methacrylate (50–66 mol%) despite the fact that the comonomers were added in equimolar amounts. Due to the layered structure of the initiator, the polymerization took place in the graphite interlayer spaces and lead to extensive delamination, indicating at the potential to produce in situ graphite/copolymer composite materials.

Macromol doi: 10.3390/macromol2020011

Authors: Girish Galgali Senthil Kumar Kaliappan Tej Pandit

Polyethylenes (PE) are the most commonly occurring ingredients for post-consumer recyclates (PCR). The structure–property relationships of different types of model PE-based blends are established using multiple thermo-rheological analyses. Although considered “simple”, the complex behavior of model PE-based blends is experimentally demonstrated for the first time for metallocene-catalyzed, linear, low-density polyethylenes (mLLDPE) with different microstructures that are commonly encountered in PCR. During non-isothermal crystallization, the microstructure of mLLDPE predominantly influences the interaction between mLLDPE and LDPE. Based on the mLLDPE microstructure, the molten LDPE phase acts either as a nucleating agent or as a crystallization rate promoting agent. Both rheological and thermal analyses show that higher activation energy is required for the reptation or movement of polymer chains in a highly branched microstructure with long chain branching (LCB) compared to a linear microstructure with short chain branching (SCB). The quasi-melt response, as measured by thermal analysis under non-isothermal conditions, is distinctly different and sensitive to both the SCB and LCB present in the LLDPE/LDPE blends.

Macromol doi: 10.3390/macromol2020010

Authors: Claudia Sergi Libera Vitiello Pietro Russo Jacopo Tirillò Fabrizio Sarasini

The automotive sector covers almost 40% of polyamide (PA) total demand. A suitable solution to improve the sustainability of this sector is the exploitation of PA matrices sourced from renewable origins, such as PA11, and their reinforcement with natural fibers such as vegetable flax and mineral basalt. A preliminary study on the quasi-static properties of PA11-based composites reinforced with an intraply flax/basalt hybrid fabric demonstrated their feasibility for semi-structural purposes in the transportation field, but their application needs to be validated against dynamic loading. In this regard, this work investigated the low-velocity impact performance of PA11 flax/basalt hybrid composites (10 J, 20 J and 30 J) as a function of temperature (room temperature and +80 °C) and plasticizer addition (butyl-benzene-sulfonamide). The results proved that plasticized PA11 is endowed with a lower glass transition temperature (~15 °C, from DMA) and melting temperature (~10 °C, from DSC), which simplifies manufacturing and processing, but also possesses a higher toughness which delays penetration phenomena and reduces permanent indentation at room temperature between 20.5% and 42.8% depending on impact energy. The occurrence of matrix plasticization at +80 °C caused a more flexible and tougher response from the laminates with a decrease in linear stiffness and a delay in penetration phenomena which made the plasticizer effect less prominent.