Sustainable polymers from biomass: Bridging chemistry with materials and processing

Laponite-Modified Biopolymers as a Conformable Substrate for Optoelectronic Devices

Biopolymers such as carboxymethyl cellulose and hyaluronic acid are alternative substrates for conformable organic light-emitting diodes (OLEDs). However, drawbacks such as mechanical stress susceptibility can hinder the device's performance under stretched conditions. To overcome these limitations, herein, we developed a nanocomposite based on CMC/HA (carboxymethyl cellulose/hyaluronic acid) and synthetic Laponite, intending to improve the mechanical strength without compromising the film flexibility and transparency (transmittance >80%; 380-700 nm) as substrates for conformable OLEDs. From XRD, FTIR, CP-MAS NMR, and TGA/DTG characterization techniques, it was possible to conclude the presence of Laponite randomly dispersed between the polymer chains. CMC/HA with 5% (w/w) Laponite, CMC/HA 5, presented a higher tensile strength (370.6 MPa) and comparable Young's modulus (51.0 ± 1.2 MPa) in comparison to the nanocomposites and pristine films, indicating a better candidate for the device's substrates. To produce the OLED, the multilayer structure ITO/MoO3/NPB/TCTA:Ir(ppy)3/TPBi:Ir(ppy)3/BPhen/LiF was deposited onto the CMC/HA 5 substrate. The OLEDs fabricated using CMC/HA 5 substrates showed higher luminance (12 kcd/m2) and irradiance (0.9 mW/cm2) values when compared with those based on commercial bacterial cellulose. However, the same device presented a lower efficiency (3.2 cd/A) due to a higher current density. Moreover, the OLED fabricated onto the Laponite-modified biopolymer presented reproducible behavior when submitted to continuous bending stress. Thus, CMC/HA 5 demonstrates potential as a transparent conductor substrate for biopolymer-based OLEDs with comparable performance to commercial bacterial cellulose features.

Recent Advancements towards Sustainability in Rotomoulding

Rotational moulding is a unique low-shear process used to manufacture hollow parts. The process is an excellent process method for batch processing, minimal waste and stress-free parts. However, the process has drawbacks such as long cycle times, gas dependency and a limited palette of materials relative to other process methods. This review aimed to shed light on the current state-of-the-art research contributing towards sustainability in rotational moulding. The scope of this review broadly assessed all areas of the process such as material development, process adaptations and development, modelling, simulation and contributions towards applications carving a more sustainable society. The PRISMA literature review method was adopted, finding that the majority of publications focus on material development, specifically on the use of waste, fillers, fibres and composites as a way to improve sustainability. Significant focus on biocomposites and natural fibres highlighted the strong research interest, while recyclate studies appeared to be less explored to date. Other research paths are process modification, modelling and simulation, motivated to increase energy efficiency, reduction in scrap and attempts to reduce cycle time with models. An emerging research interest in rotational moulding is the contribution towards the hydrogen economy, particularly type IV hydrogen vessels.

Synthesis of Bio-Based Polyester Resins for Vat Photopolymerization 3D Printing

Driven by environmental considerations, the scientific community has directed great effort towards the synthesis of new materials derived from renewable resources. However, for photocurable resins, most commercially available building blocks still rely on petroleum-based precursors. Herein, we present a simple synthesis route for bio-based acrylate-modified polyester resins, whose viscosity is sufficiently low for processing them with vat photopolymerization 3D printing. The established synthesis route enables the gradual substitution of fossil-based raw materials with bio-based alternatives. The acid number, color and viscosity of the bio-based acrylic resins are characterized and photocurable formulations are prepared by adding a radical photoinitiator. The photopolymerization kinetics, and thermomechanical and mechanical properties of the photopolymers are investigated as a function of the resin structure and benchmarked against a commercially available petroleum-based counterpart. Finally, the processability of the new bio-based resins via digital light processing 3D printing is demonstrated and test specimens are successfully 3D printed with a resolution in the millimeter range.

Novel green-based polyglycerol polymeric nanoparticles loaded with ferulic acid: A promising approach for hepatoprotection

In the pursuit of eco-friendly and sustainable materials, polyglycerol diacid polymers hold immense promise for drug delivery compared to those derived from fossil fuels. Harnessing this potential, we aimed to prepare nanoparticles (NPs) derived from sustainable polymers, loaded with ferulic acid (FA), a natural polyphenolic compound known for its shielding effect against liver-damaging agents, including carbon tetrachloride (CCl4). Glycerol was esterified with renewable monomers, such as succinic acid, adipic acid, and/or FA, resulting in the creation of a novel class of polyglycerol diacid polymers. Characterization via Fourier-transform infrared spectroscopy and nuclear magnetic resonance confirmed the successful synthesis of these polymers with <7 % residual monomers. FA-loaded NPs were fabricated using the newly synthesized polymers. To further augment their potential, the NPs were coated with chitosan. The chitosan-coated NPs boasted an optimal PS of 290 ± 5.03 nm, showing superior physical stability, and a commendable EE% of 58.79 ± 0.43%w/v. The cytotoxicity was examined on fibroblast cells using the SRB assay. In-vivo experiments employing a CCl4-induced liver injury model yielded compelling evidence of the heightened hepatoprotective effects conferred by chitosan-coated particles. This demonstrates the benefits of incorporating sustainable polymers into innovative composites for efficient drug delivery, indicating their potential for creating versatile platforms for various therapeutic applications.

Poly(ethylene succinate-co-lactic acid) as a Multifunctional Additive for Modulating the Miscibility, Crystallization, and Mechanical Properties of Poly(lactic acid)

Polymer blending offers an effective and economical approach to overcome the performance limitations of poly(lactic acid) (PLA). In this study, a series of copolymers poly(ethylene succinate-co-lactic acid) (PESL) were synthesized, featuring lactic acid (LA) contents that ranged from 20 to 86 wt %. This synthesis involved a one-pot industrial melt polycondensation process using succinic acid (SA), ethylene glycol (EG), and LA, catalyzed by titanium tetraisopropoxide (TTP). The goal was to produce a fully biobased copolymer expected to exhibit partial miscibility with pure poly(lactic acid) (PLA). To assess the capability of PESL copolymers in toughening PLA, we conducted tensile testing on PLA/PESL blends containing 15 wt % PESL. As a result, an elongation at break for the blends with 15 wt % loading of the copolymer PESL72 was directly enhanced to 250% with an ultimate strength of 35 MPa, compared to brittle PLA with less 10% tensile length. The morphological features of interfacial adhesion before and after tensile failure were measured by scanning electron microscopy (SEM). A significant enhancement in the chain mobility of the PLA/PESL blends was further evidenced by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). These findings hold promise for the development of functional packaging materials based on PLA. The proposed copolymer design, which boasts strong industrial feasibility, can serve as a valuable guide for enhancing the toughness of PLA.

Facile preparation of near-monodisperse oligocellulose and its elastomeric derivatives with tunable mechanical properties

Oligocellulose (OC) with low polydispersity indices has been produced in large quantities using an improved method of acid-assisted hydrolysis, in which long cellulose chains disintegrate in concentrated phosphoric acid at moderately elevated temperatures. The hydrolysis time has been reduced by three orders of magnitude without compromising the overall yield of the process or the quality of OC products. The efficient production of high-quality OCs in large quantities allows for developing OC-derived elastomeric materials. A series of OC-graft-poly(isobornyl methacrylate-random-n-butyl acrylate) [OC-g-P(IBOMA-r-BA)] elastomers have been synthesized via activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP). OC-g-P(IBOMA-r-BA) elastomers have tunable molecular architectures and phase morphologies toward desirable mechanical properties and thermal stability suitable for various applications. The methodologies of the OC production and the graft-polymers synthesis in this study would help advance technologies for broader applications of bio-based elastomers.

Biomass-Derived Degradable Polymers via Alternating Ring-Opening Metathesis Polymerization of Exo-Oxanorbornenes and Cyclic Enol Ethers

Degradable polymers made via ring-opening metathesis polymerization (ROMP) hold tremendous promise as eco-friendly materials. However, most of the ROMP monomers are derived from petroleum resources, which are typically considered less sustainable compared to biomass. Herein, we present a synthetic strategy to degradable polymers by harnessing alternating ROMP of biomass-based cyclic olefin monomers including exo-oxanorbornenes and cyclic enol ethers. A library of well-defined poly(enol ether)s with modular structures, tunable glass transition temperatures, and controlled molecular weights was achieved, demonstrating the versatility of this approach. Most importantly, the resulting copolymers exhibit high degrees of alternation, rendering their backbones fully degradable under acidic conditions.

Mechanism Study of the Polymerization of Polyamide 56: Reaction Kinetics and Process Parameters

Polyamide 56 (PA56) has gained significant attention in the academic field due to its remarkable mechanical and thermal properties as a highly efficient and versatile biobased material. Its superior moisture absorption property also makes it a unique advantage in the realm of fiber textiles. However, despite extensive investigations on PA56's molecular and aggregate state structure, as well as processing modifications, little attention has been paid to its polymerization mechanism. Herein, the influence of temperature and time on PA56's polycondensation reaction is detailed studied by end-group titration and carbon nuclear magnetic resonance (NMR) techniques. The reaction kinetics equations for the pre-polymerization and vacuum melt-polymerization stages of PA56 are established, and possible side reactions during the polycondensation process are analyzed. By optimizing the reaction process based on kinetic characteristics, PA56 resin with superior comprehensive properties (melting temperature of 252.6 °C, degradation temperature of 371.6 °C, and tensile strength of 75 MPa) is obtained. The findings provide theoretical support for the industrial production of high-quality biobased PA56.

Sustainable formulation polymers for home, beauty and personal care: challenges and opportunities

As society moves towards a net-zero future, the need to adopt more sustainable polymers is well understood, and as well as plastics, less visible formulation polymers should also be included within this shift. As researchers, industries and consumers move towards more sustainable products there is a clear need to define what sustainability means in fast moving consumer goods and how it can be considered at the design stage. In this perspective key challenges in achieving sustainable formulation polymers are highlighted, and opportunities to overcome them are presented.

Visualizing Chain Growth of Polytelluoxane via Polymerization Induced Emission

Visualizing polymer chain growth is always a hot topic for tailoring structure-function properties in polymer chemistry. However, current characterization methods are limited in their ability to differentiate the degree of polymerization in real-time without isolating the samples from the reaction vessel, let alone to detect insoluble polymers. Herein, a reliable relationship is established between polymer chain growth and fluorescence properties through polymerization induced emission. (TPE-C2)2 -Te is used to realize in situ oxidative polymerization, leading to the aggregation of fluorophores. The relationship between polymerization degree of growing polytelluoxane (PTeO) and fluorescence intensity is constructed, enabling real-time monitoring of the polymerization reaction. More importantly, this novel method can be further applied to the observation of the polymerization process for growing insoluble polymer via surface polymerization. Therefore, the development of visualization technology will open a new avenue for visualizing polymer chain growth in real-time, regardless of polymer solubility.

Development of poly(methyl methacrylate)/poly(lactic acid) blend as sustainable biomaterial for dental applications

Poly(lactic acid) (PLA) is gaining popularity in manufacturing due to environmental concerns. When comparing to poly(methyl methacrylate) (PMMA), PLA exhibits low melting and glass transition temperature (Tg). To enhance the properties of these polymers, a PMMA/PLA blend has been introduced. This study aimed to investigate the optimal ratio of PMMA/PLA blends for potential dental applications based on their mechanical properties, physical properties, and biocompatibility. The PMMA/PLA blends were manufactured by melting and mixing using twin screw extruder and prepared into thermoplastic polymer beads. The specimens of neat PMMA (M100), three different ratios of PMMA/PLA blends (M75, M50, and M25), and neat PLA (M0) were fabricated with injection molding technique. The neat polymers and polymer blends were investigated in terms of flexural properties, Tg, miscibility, residual monomer, water sorption, water solubility, degradation, and biocompatibility. The data was statistically analyzed. The results indicated that Tg of PMMA/PLA blends was increased with increasing PMMA content. PMMA/PLA blends were miscible in all composition ratios. The flexural properties of polymer blends were superior to those of neat PMMA and neat PLA. The biocompatibility was not different among different composition ratios. Additionally, the other parameters of PMMA/PLA blends were improved as the PMMA ratio decreased. Thus, the optimum ratio of PMMA/PLA blends have the potential to serve as novel sustainable biomaterial for extensive dental applications.

Solvent-Free Environmentally Friendly Method to Prepare Thermo-Reversible Fully Bio-Based Elastomers

Most rubber products come from petrochemical resources, which are increasingly in short supply. Rubber products that formed irreversible chemical bonds in the vulcanization process are difficult to recycle, resulting in a serious waste of resources. Therefore, it is important to prepare a kind of reprocessable biobased elastomers. Using furfuryl methacrylate (FMA) as the modified monomer, poly(dibutyl itaconate-myrcene-furfuryl methacrylate) (PDBIMFA) was synthesized by high-temperature emulsion polymerization successfully. The structure and compositions of PDBIMFA were characterized by Fourier transform infrared and 1H NMR, and the effects of different FMA contents on the structures and properties of PDBIMFA were systematically studied. Based on the Diels-Alder reaction, bismaleimide (BMI) and carbon black (CB) were introduced into PDBIMFA as cross-linking agents and reinforcing fillers, respectively, by the melt blending method, and PDBIMFA-BMI elastomer materials and CB/PDBIMFA-BMI elastomer composites with thermo-reversible cross-linking characteristics were prepared. The effects of the ratio of FMA and BMI on the mechanical properties of PDBIMFA-BMI were studied. PDBIMFA-BMI and CB/PDBIMFA-BMI were reprocessed twice, and the recovery rate of tensile strength was both more than 90%. The addition of CB was found to play a reinforcing role in the elastomer and with the introduction of the amount of CB, the reprocessability of composite remained at a good level. It is hoped that this research will provide a new strategy for the sustainable development of bio-based elastomer materials.

Circular Production, Designing, and Mechanical Testing of Polypropylene-Based Reinforced Composite Materials: Statistical Analysis for Potential Automotive and Nuclear Applications

The circularity of polymer waste is an emerging field of research in Europe. In the present research, the thermal, surface, mechanical, and tribological properties of polypropylene (PP)-based composite produced by injection molding were studied. The pure PP matrix was reinforced with 10, 30, and 40% wt. of pure cotton, synthetic polyester, and polyethylene terephthalate post-consumer fibers using a combination of direct extrusion and injection molding techniques. Results indicate that PP-PCPESF-10% wt. exhibits the highest value of tensile strength (29 MPa). However, the values of tensile and flexural strain were lowered with an increase in fiber content due to the presence of micro-defects. Similarly, the values of modulus of elasticity, flexural modulus, flexural strength, and impact energy were enhanced due to an increase in the amount of fiber. The PP-PCCF-40% wt. shows the highest values of flexural constant (2780 MPa) and strength (57 MPa). Additionally, the increase in fiber loadings is directly proportional to the creation of micro-defects, surface roughness, abrasive wear, coefficient of friction, and erosive wear. The lowest average absolute arithmetic surface roughness value (Ra) of PP and PP-PCCF, 10% wt., were 0.19 µm and 0.28 µm. The lowest abrasive wear value of 3.09 × 10-6 mm3/Nm was found for pure PP. The erosive wear value (35 mm3/kg) of PP-PCCF 40% wt. composite material was 2 to 17 times higher than all other composite materials. Finally, the single-step analysis of variance predicts reasonable results in terms of the p-values of each composite material for commercial applications.

Biobased Intelligent Food-Packaging Materials with Sustained-Release Antibacterial and Real-Time Monitoring Ability

It has been widely accepted that sustainable polymers derived from renewable resources are able to replace the short-turnover petroleum-based materials and reduce environmental impact in the future. However, their hydrophilic chemical structures rich with oxygen groups could lead to easy growth of bacteria, which greatly limit their applications in packaging materials. Here, we present an intelligent food-packaging material with sustained-release antibacterial and real-time monitoring ability based on totally biobased contents. In detail, sodium alginate with Artemisia argyi emission oil (encapsulated in gelatin-Arabic gum microcapsules) and citric acid-sourced pH-responsive carbon quantum dots (CQDs) are coated on bamboo cellulose papers. The obtained biobased composite material (almost 100% biocarbon content) with antibacterial ability is able to extend the shelf life of fresh shrimps and can be biodegraded. Moreover, owing to the introduction of CQDs, the composite can rapidly (within 1 s) detect slight pH variations (response pH ∼5, 10-9 mol/L of OH-) through an obvious color change (hue value from 305 to 355°). The developed strategy may open up new opportunities in the design of multifunctional biobased composites for intelligent applications.

Fast Fabrication of Porous Amphiphilic Polyamides via Nonconventional Evaporation Induced Phase Separation

In the present work, we report a facile approach for the fast fabrication of porous films and coatings of long-chain polyamides through a nonconventional evaporation induced phase separation. Because of its amphiphilic nature, polyamide 12 can be dissolved in the mixture of a high-polarity solvent and a low-polarity solvent, while it could not be dissolved in either solvent solely. The sequential and fast evaporation of the solvents leads to the formation of porous structures within 1 min. Moreover, we have investigated the dependence of the pore structures on composition of the solutions, and have demonstrated that our approach can be applied to other long-chain polycondensates, too. Our findings can provide insight on the fabrication of porous materials by using amphiphilic polymers.

Bio-sorbent from castor oil polyurethane foam containing cellulose-halloysite nanocomposite for removal of manganese, nickel and cobalt ions from water

In order to mitigate the contamination of water with heavy metals, caused by mining dam failures in Brumadinho and Mariana in Brazil, eco-friendly bio-based castor oil polyurethane foams, containing a cellulose-halloysite green nanocomposite were prepared. Polyurethane foams containing none (PUF-0), 5%wt (PUF-5), and 10%wt (PUF-10) of the nanocomposite were obtained. The application of the material in aqueous media was verified through an investigation of the efficiency of adsorption, the adsorption capacity, and the adsorption kinetics in pH= 2 and pH= 6.5 for manganese, nickel, and cobalt ions. An increase of 5.47 times in manganese adsorption capacity was found after only 30 min in contact with a solution having this ion at pH= 6.5 for PUF-5 and 11.38 times for PUF-10 when both were compared with PUF-0. Adsorption efficiency was respectively 68.17% at pH= 2 for PUF-5% and 100% for PUF-10 after 120 h, while for the control foam, PUF-0, the adsorption efficiency was only 6.90%.

Fully biobased sustainable elastomers derived from chitin, lignin, and plant oil via grafting strategy and Schiff-base chemistry

With the dramatically increased environmental problems, the rational design of sustainable polymers from renewable feedstocks opens new avenues to reduce the huge pollution impact. The major challenge for sustainable polymers is the decreased mechanical performance compared to that of petroleum-based materials. In this work, fully biobased sustainable elastomers were developed by integrating renewable chitin, lignin, and plant oil into one macromolecule, in which chitin was chosen as the rigid backbone, while a lignin-derived monomer vanillin acrylate (VA) and a plant oil-based monomer lauryl acrylate (LA) were selected as the hard and soft segments for the grafted side chains. A series of Chitin-graft-poly(vanillin acrylate-co-lauryl acrylate) (Chitin-g-P(VA-co-LA)) copolymers with varied feed ratios and chitin contents were synthesized by using reversible addition-fragmentation chain transfer (RAFT) polymerization as an effective grafting strategy. In addition, a dynamic cross-linked network was incorporated via Schiff-base reaction to improve the macroscopic behavior of such kind of chitin graft elastomers. These sustainable elastomers are mechanically strong and show excellent reprocessablity, as well as outstanding UV-blocking property. This strategy is versatile and can inspire the further development of fully biobased sustainable materials from natural resources.

ReaxFF molecular dynamics simulation of the thermal decomposition reaction of bio-based polyester materials

Bio-based polyester elastomers have been widely studied by researchers in recent years because of their comprehensive sources of monomers and environmentally friendly characteristics. However, compared with traditional petroleum-based elastomers, the thermal decomposition temperature of bio-based polyester elastomers is generally low, limiting the application of bio-based elastomers. An effective strategy to increase the intrinsic thermal decomposition temperature (T_d) of bio-based elastomers is to increase the length of the monomer carbon chain in the bio-based elastomers. In this work, the content of dodecanedioic acid (DDA) in a bio-based polyester elastomer composed of butanediol (BDO) and succinic acid (SUA) was increased to improve the T_d of the bio-based polyester elastomer through the reaction force-field molecular dynamics (ReaxFF-MD) simulations. And the thermal decomposition mechanism of the bio-based polyester was analyzed in detail. By calculating the change rate of the molecular chain mean square displacement (MSD), it was determined that when the content of DDA was 50%, the T_d of the bio-based elastomer was up to 718 K. By calculating the activation energy of thermal decomposition and further analyzing the thermal decomposition process, it is found that the thermal decomposition of the bio-based polyester elastomer is mainly through breaking the C-O bond in the backbone. This work is expected to provide theoretical guidance for designing and fabricating highly heat-resistant bio-based elastomers by systematically exploring the thermal decomposition mechanism of bio-based polyester elastomers.

High-performance arabinoglucuronoxylan-based biosurfactants for oily sludge separation

Arabinoglucuronoxylan (AGX), an important carbohydrate polymer in lignocellulosic biomass, contains many functional groups. It has excellent amphiphilic modification properties and has potential application in the separation of oily sludge. In this study, a simple strategy for producing high-performance AGX-based biosurfactants was studied and the raw AGX was extracted from bamboo by hydrothermal treatment. AGX-based biosurfactants with amphiphilic structure were produced by AGX and dodecanal succinic anhydride (DDSA) using rapid homogeneous esterification reactions in deep eutectic solvents (DES). This resulted in a significant reduction in the surface tension of the water from 72.32 to 29.76 mN·m^-1. These parameters are similar to those achieved using sodium dodecyl sulfate (SDS), a widely employed synthetic surfactant. Other physicochemical properties, including foamability, emulsification activity, stability, solubilization, and detergency were significantly improved compared to the unmodified AGX, demonstrate that AGX-based biosurfactants are promising detergents for oily sludge remediation and oil recovery. The results provide a new pathway for high value utilization of arabinoglucuronoxylan.

Binary solvent-exchange-induced self-assembly of silk fibroin birefringent fibers for optical applications

To generate birefringence in artificial materials has attracted increasing attention in terms of their potential for applications in sensor, tissue engineering and optical devices. Silk materials with patterned structures presented unique optical features, however, effectively fabricating of structural anisotropy in silk materials to directly tailor their birefringence is still challenging. Silk fibroin birefringent fibers (SBFs) with tunable birefringence were obtained in this study via a strategy that combined injection technique and binary solvent-exchange-induced self-assembly (BSEISA). The structural deformation of these SBFs that introduced by external stimulus such as tensile and solvent swelling was critical to their birefringence. As a result, pink, yellow, green, cyan, and purple were successfully achieved in the interference color of the SBFs with an exchanging solvent of 25, 55, 75, 90 wt% ethanol aqueous solution, and methanol respectively. Moreover, we respectively exchanged these SBFs against with Congo red (SBF-CR), methyl orange (SBF-MO), methylene blue (SBF-MB) and rhodamine B (SBF-RhB) solutions to produce fibers with diversity in their birefringent performance. Two types of patterns were designed and thereafter constructed by (1) SBF\SBF-CR\SBF-RhB, and (2) SBF\SBF-MB\SBF-CR. Interestingly, the patterns both displayed a letter of "A" in natural light, while displayed different letters of (1) "H" and (2) "U" in polarized light. This study demonstrated that these SBFs with unique optical and birefringent performances are anticipated to act as sensors and code labels for optical applications.

Repurposing of waste PET by microbial biotransformation to functionalized materials for additive manufacturing

Plastic waste is an outstanding environmental thread. Poly(ethylene terephthalate) (PET) is one of the most abundantly produced single-use plastics worldwide, but its recycling rates are low. In parallel, additive manufacturing is a rapidly evolving technology with wide-ranging applications. Thus, there is a need for a broad spectrum of polymers to meet the demands of this growing industry and address post-use waste materials. This perspective article highlights the potential of designing microbial cell factories to upcycle PET into functionalized chemical building blocks for additive manufacturing. We present the leveraging of PET hydrolyzing enzymes and rewiring the bacterial C2 and aromatic catabolic pathways to obtain high-value chemicals and polymers. Since PET mechanical recycling back to original materials is cost-prohibitive, the biochemical technology is a viable alternative to upcycle PET into novel 3D printing materials, such as replacements for acrylonitrile butadiene styrene. The presented hybrid chemo-bio approaches potentially enable the manufacturing of environmentally friendly degradable or higher-value high-performance polymers and composites and their reuse for a circular economy.

ONE-SENTENCE SUMMARY

Biotransformation of waste PET to high-value platform chemicals for additive manufacturing.

Simple lignin-based, light-driven shape memory polymers with excellent mechanical properties and wide range of glass transition temperatures

Lignin is the most abundant biomass source of aromatic hydrocarbons but, at present, is not effectively utilized. The development of simple and efficient methods for producing lignin-based polymers to replace petroleum-based products is an important strategy for promoting environmentally friendly and sustainable materials and controlling carbon emissions. In this work, lignin-based, light-driven shape memory polymers (ELIDs) with improved mechanical properties have been prepared from enzymatic hydrolysis lignin, itaconic acid and 1,12-dodecanediol, without any chemical modification of the lignin. The polymers contain large proportions of lignin (20-40 wt%, designated ELID20 to ELID40) and their mechanical properties are dependent on the lignin content. Maximum tensile strength (46.9 MPa) was achieved with ELID30, maximum elongation at break (93.7 %) was achieved with ELID20 and highest fracture energy (10.75 J cm^-3) was achieved with ELID25. These excellent mechanical properties are accompanied by good thermal stability and a wide range of glass transition temperatures (21.2-157.3 °C), supporting a broad range of applications. The shape fixation rate (R_f) and shape recovery rate (R_r) were highest for ELID30 (98.7 % and 97.4 %, respectively). Under 1 sun simulated solar irradiation, ELID20 reached a temperature exceeding the glass transition temperature in 15 s and, under 3 sun simulated solar irradiation, ELID30 reached a temperature of 130 °C and shape recovered in 60 s. The excellent mechanical properties and good light-driven shape memory of ELIDs provide inspiration for the development and utilization of lignin-based polymers.

Predictive Molecular Design and Structure-Property Validation of Novel Terpene-Based, Sustainably Sourced Bacterial Biofilm-Resistant Materials

Presented in this work is the use of a molecular descriptor, termed the α parameter, to aid in the design of a series of novel, terpene-based, and sustainable polymers that were resistant to biofilm formation by the model bacterial pathogen Pseudomonas aeruginosa. To achieve this, the potential of a range of recently reported, terpene-derived monomers to deliver biofilm resistance when polymerized was both predicted and ranked by the application of the α parameter to key features in their molecular structures. These monomers were derived from commercially available terpenes (i.e., α-pinene, β-pinene, and carvone), and the prediction of the biofilm resistance properties of the resultant novel (meth)acrylate polymers was confirmed using a combination of high-throughput polymerization screening (in a microarray format) and in vitro testing. Furthermore, monomers, which both exhibited the highest predicted biofilm anti-biofilm behavior and required less than two synthetic stages to be generated, were scaled-up and successfully printed using an inkjet "valve-based" 3D printer. Also, these materials were used to produce polymeric surfactants that were successfully used in microfluidic processing to create microparticles that possessed bio-instructive surfaces. As part of the up-scaling process, a novel rearrangement was observed in a proposed single-step synthesis of α-terpinyl methacrylate via methacryloxylation, which resulted in isolation of an isobornyl-bornyl methacrylate monomer mixture, and the resultant copolymer was also shown to be bacterial attachment-resistant. As there has been great interest in the current literature upon the adoption of these novel terpene-based polymers as green replacements for petrochemical-derived plastics, these observations have significant potential to produce new bio-resistant coatings, packaging materials, fibers, medical devices, etc.

Fully Bio-based Poly(ketal-ester)s by Ring-opening Polymerization of a Bicylcic Lactone from Glycerol and Levulinic Acid

A fully renewable bio-based bicyclic lactone containing a five-membered cyclic ketal moiety, 7-methyl-3,8,10-trioxabicyclo[5.2.1]decan-4-one (TOD), was synthesized through a two-step acid-catalyzed process from glycerol and levulinic acid. The ring-opening polymerization (ROP) of TOD at 30°C with benzyl alcohol (BnOH) as the initiator and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the catalyst can afford high molar mass PTOD with a cis-2.4-disubstitued 2-methyl 1,3-dioxolane moiety in its repeating unit. PTOD is an amorphous polymer with a glass transition temperature (T_g ) of 13°C. It can be hydrolyzed into structurally defined small molecules under acidic or basic conditions by the selective cleavage of either the cyclic ketal or the ester linkage respectively. The TBD-catalyzed copolymerization of L-lactide (L-LA) and TOD at -20°C was investigated. It was confirmed that L-LA polymerized quickly with racemization to form PLA, followed by a slow incorporation of TOD into the formed PLA chains via transesterification. By varying the feed ratios of L-LA to TOD, a series of random copolymers (PLA-co-PTOD) with different TOD incorporation ratios and tunable T_g s were obtained. Under acidic conditions, PLA-co-PTOD degrades much faster than PLA via the selective cleavage of the cyclic ketal linkages. This work provides insights for the development of more sustainable and acid-accelerated degradable alternatives to aliphatic polyesters.

Covalent Cross-Linking as a Strategy to Prepare Water-Dispersible Chitosan Nanogels

Due to the environmental problems generated by petroleum derivative polymers as mentioned in Agenda 2030, the use of natural polymers is increasing. Among them, cellulose and chitin are the most widespread biopolymers available in nature. Chitosan, obtained from chitin, is a really good candidate to develop nanocarriers due to its polyelectrolyte nature and ease of chemical modification. However, chitosan presents a solubility drawback in an aqueous medium at physiological pH (pH = 7.4), which restricts its applicability in biomedicine. In this work, nanogels were successfully synthesized from chitosan systems with different water solubilities (chitosan, oligosaccharide chitosan, and quaternized chitosan) using the reverse microemulsion method and polyethylene glycol diacid (PEGBCOOH) as a covalent cross-linking agent. Cross-linking with PEGBCOOH was analyzed by proton nuclear magnetic resonance (¹H-NMR), which allowed for nanogels to be prepared whose size and swelling were comparatively studied by transmission electron microscopy (TEM) and dynamic light scattering (DLS) and zeta potential, respectively. The particle size of the swollen nanogels showed a different pH-responsive behavior that decreased for chitosan, increased for oligosaccharide chitosan, and remained constant for quaternized chitosan. Nevertheless, a drastic reduction was observed in all cases in the culture medium. Along the same line, the dispersibility of the synthesized nanogels in different media was comparatively evaluated, showing similar values for the nanogels prepared from soluble chitosans than for water insoluble chitosan as a consequence of the cross-linking with PEGBCOOH. After 6 months of storage of the dried nanogels, the water dispersibility values remained constant in all cases, demonstrating the stabilizing effect of the employed cross-linking agent and the potential use of synthesized nanogels as substrates for drug delivery.

Aptamer-Gated Mesoporous Silica Nanoparticles for N Protein Triggered Release of Remdesivir and Treatment of Novel Coronavirus (2019-nCoV)

Since the 2019-nCoV outbreak was first reported, hundreds of millions of people all over the world have been infected. There is no doubt that improving the cure rate of 2019-nCoV is one of the most effective means to deal with the current serious epidemic. At present, Remdesivir (RDV) has been clinically proven to be effective in the treatment of SARS-CoV-2. However, the uncertain side effects make it important to reduce the use of drugs while ensuring the self-healing effect. We report an approach here with targeted therapy for the treatment of SARS-CoV-2 and other coronaviruses illness. In this study, mesoporous silica was used as the carrier of RDV, the nucleocapsid protein (N protein) aptamer was hybridized with the complementary chain, and the double-stranded DNA was combined with gold nanoparticles as the gates of mesoporous silica pores. When the RDV-loaded mesoporous silica is incubated with the N protein, aptamer with gold nanoparticles dissociate from the complementary DNA oligonucleotide on the mesoporous silica surface and bind to the N protein. The releasing of RDV was determined by detecting the UV-vis absorption peak of RDV in the solution. These results show that the RDV delivery system designed in this work has potential clinical application for the treatment of 2019-nCoV.

Fabrication Mechanisms of Lignin Nanoparticles and Their Ultraviolet Protection Ability in PVA Composite Film

Lignin is an indispensable and essential compound present in plants. It is a renewable resource and a green alternative to traditional petroleum energy. The rational utilization of lignin can reduce the environmental damage caused by traditional industrial development. The preparation of lignin nanoparticles (LNPs) using the self-assembly method is one of the most favorable ways to achieve high value-added utilization of lignin. However, the process requires an in-depth understanding of the sphere-forming mechanism of lignin self-assembly and the interaction of self-assembly forces. We used the same raw materials and two different preparation methods to prepare LNPs. The results revealed that the variation in the order of the dropwise addition of lignin solution and deionized water produced LNPs with varying average sizes. The sphere-forming mechanisms of the two kinds of lignin nanoparticles were discussed for the preparation of UV-resistant polyvinyl alcohol (PVA) polymeric films. During lignin spherification, the faster the solution reaches the supersaturation state, the faster the spherogenesis rate is, the smaller the size is, and the narrower the particle size distribution is. The lignin micro/nanospheres are produced by exploiting the π-π bonding interactions in lignin itself. The lignin micro/nanospheres are then mixed with PVA to form a film to obtain a lignin-PVA composite film material with an anti-UV effect.

Modifying Anti-Compression Property and Water-Soluble Ability of Polyglycolic Acid via Melt Blending with Polyvinyl Alcohol

Biodegradable polymeric materials have become the most attractive research interest in recent years and are gradually widely used in various fields in the case of environmental pollution. In this paper, binary blends, mainly including varying contents of polyglycolic acid (PGA) and poly(vinyl alcohol) (PVA), were prepared via a melt compounding strategy. The ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA) was employed as the compatibilizer to improve the compatibility between the PGA and PVA and the polyolefin elastomer (POE) was used as toughening agent. The anti-compression property and water-soluble ability of the blends were particularly studied to explore their potential application in an oil/gas exploitation field. Special attentions were paid to the evolution of the water-soluble ability of PGAX with the PVA concentration. Furthermore, isothermal shear measurement and thermogravimetric analysis were performed to evaluate the thermal stability of PGA and PGA blends (PGAX) during melt processing. The results showed that the incompatibility between PGA and PVA largely deteriorated the mechanical property, i.e., anti-compression strength, leading to fragile characteristics under a lower compressive load for the PGAX samples with varied contents of PVA. The presence of PVA and EMA-GMA greatly enhanced the viscoelasticity of the PGA melt, showing an increased storage modulus and viscosity at a low shear frequency; however, the thermal instability of PGAX was intensified owing to the greater ease of thermal degradation of PVA than that of PGA. Meanwhile, the water-soluble ability of PGAX was improved due to the high water dissolution of PVA, which played the role as a sacrificial material. The purpose of this work is to pursue an effective modification for PGA processing and application via melt blending.

Reorganization of Hydrogen Bonding in Biobased Polyamide 5,13 under the Thermo-Mechanical Field: Hierarchical Microstructure Evolution and Achieving Excellent Mechanical Performance

The hierarchical microstructure evolution of an emerging biobased odd-odd polyamide 5,13 (PA5,13) films under the thermo-mechanical field, stepping from hydrogen bond (H-bond) arrangement to the crystalline morphology, has been investigated systematically. It is found that the reorganization of H-bonds under the thermo-mechanical field plays a crucial role in the crystallization of PA5,13. Especially, it is revealed that the crystallization process under the thermo-mechanical field develops along the chain axis direction, while lamellar fragmentation occurs perpendicular to the chain axis. Consequently, a stable and well-organized H-bond arrangement and lengthened lamellae with significant orientation have been constructed. Laudably, an impressive tensile strength of about 500 MPa and modulus of about 4.7 GPa are thus achieved. The present study could provide important guidance for the industrial-scale manufacture of high-performance biobased odd-odd PAs with long polymethylene segment in the dicarboxylic unit combined with a large difference between the polymethylene segments in the dicarboxylic and diamine units.

Improving the Wet-Spinning and Drawing Processes of Poly(lactide)/Poly(ethylene furanoate) and Polylactide/Poly(dodecamethylene furanoate) Fiber Blends

This work aims to produce poly(lactic acid) (PLA)/poly(alkylene furanoate)s (PAF)s fiber blends for textile applications and evaluates their microstructural, chemical, thermal, and mechanical properties. The work focuses on two PAFs with very different alkyl chain lengths, i.e., poly(ethylene 2,5−furandicarboxylate) (PEF) and poly(dodecamethylene 2,5−furandicarboxylate) (PDoF), which were blended in solution at various concentrations (in the range 2.5–10 wt %) with PLA, wet spun, and subsequently drawn. Light optical micrographs highlight that PLA/PEF blends present large and concentrate PEF domains, whereas PLA/PDoF blends show small and homogeneously distributed PDoF domains. The blends appear to be immiscible, which is confirmed also by scanning electron microscopy (SEM), Fourier−Transform Infrared (FT−IR) spectroscopy, and differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) highlights that the addition of the PAFs improves the thermal stability of the fibers. The drawing process, which was carried out at 80 °C with a heat setting step at 95 °C and at three draw ratios, improves the mechanical properties of the fibers upon the addition of the PAFs. The results obtained in this study are promising and may serve as a basis for future investigations on these novel bio−based fiber blends, which can contribute to increase the environmental sustainability of industrial textiles.

Polyphenol modified natural collagen fibrous network towards sustainable and antibacterial microfiltration membrane for efficient water disinfection

Because of their low-cost and high bacterial interception efficiency, large-scale membrane separation technologies like microfiltration (MF) have been widely implemented for water disinfection. However, lack of antibacterial ability and low sustainability are two major drawbacks of most petroleum-based MF membranes, which are normally associated with hazardous issues including biofouling and nonbiodegradable waste. In this work, abundant animal hides, which are by-products of the meat processing industry, were proposed as raw materials to fabricate a sustainable MF membrane due to their natural, hierarchical, and renewable collagen fibrous network (CFN) with inherent biodegradability. After the removal of non-collagen compositions from animal hides, such as hair and fat, through a facile pretreating process base on green chemistry principles, a thin CFN based membrane (CFN-M) with a similar micropore size to that of commercial MF membranes could be produced. Furthermore, inspired by conventional leather tanning technology, tannic acids (TA) were selected as plant polyphenol tanning agent to modify collagen fibers based on tanning chemistry to improve the thermal stability of CFN-M. Moreover, the TA cross-linked CFN-M (TA@CFN-M) exhibited excellent antibacterial properties due to the production of reactive oxygen species (ROS) by the catechol functional group. The resulting TA@CFN-M achieved >99.9% water disinfection efficiency with a flux of ∼150 L m^-2 h^-1 via gravity-driven operation, while simultaneously showing admirable anti-biofouling ability. Different from the commercial MF membrane, based on the green chemistry principle, this work may shed light on designing new sustainable and antibacterial membranes for anti-biofouling water disinfection.

Research Progress on the Preparation and High-Value Utilization of Lignin Nanoparticles

Lignin nanoparticles, the innovative achievements in the development and utilization of lignin, combine the structural characteristics of nanomaterials and lignin molecules and have a wide range of applications. In this review, we summarize the methods for preparing lignin nanoparticles by solvent exchange method, mechanical method, biological enzymatic method, interface polymerization/crosslinking method, and spray freezing method, and emphatically introduce the application prospects of lignin nanoparticles in ultraviolet protection, antibacterial, nano-filler, drug delivery, and adsorption, aiming to provide a certain reference direction for additional high-value applications of lignin nanoparticles.