Seawater-Degradable Polymers-Fighting the Marine Plastic Pollution

In vivo and in vitro degradation and biological toxicity studies of polyesters with varying degradation rates

The fragmentation of biodegradable plastics into "degradable particles" is an essential step during their degradation process. Investigating their in vivo degradation behaviors and toxicity differing from microplastics holds significant implications. In this study, we selected biodegradable polyesters with distinct degradation rates-polyglycolic acid (PGA) and its copolymer poly(butylene succinate-co-glycolate) (PBSG)-alongside non-biodegradable polyethylene terephthalate (PET) as a control. Using combined in vitro simulations and animal experiments, we assessed their degradation in simulated body fluid (SBF), simulated gastric fluid (SGF), simulated intestinal fluid (SIF) and toxicity effects on rat body weight and multiple organs (heart, liver, spleen, stomach, lung, kidney, colon, brain). Results showed PET exhibited negligible degradation and the highest biotoxicity. After 18 weeks, PGA demonstrated degradation rates of 53.28 % (SBF), 96.35 % (SGF), and 76.14 % (SIF), while PBSG degraded at 7.98 %, 10.28 %, and 10.42 %, respectively. Biodegradable plastics caused no significant toxicity at low doses. However, high doses induced weight loss, tissue necrosis and inflammation in rats. Notably, PGA-with the fastest degradation-showed the weakest physiological toxicity. These findings highlight the important relationship between the degradation rate of biodegradable plastics and their biotoxicity, and can guide the development of new materials to balance environmental benefits and minimized health risks.

Rayon fibre rope: A biodegradable alternative for marine use?

Rayon fibres are well-known materials that were primarily utilised as reinforcement in tyres. Today these materials are perceived as a promising substitute for synthetic fibres, exhibiting good mechanical characteristics and biodegradation in many environments. This paper investigates their potential use for marine structures. It first describes the tensile properties of the fibres and their derived yarns and ropes. These properties are then monitored during seawater ageing and the ultimate biodegradation is characterised by respirometry tests. Both material scales demonstrate rapid degradation rates under biotic conditions (90 % strength reduction after 2 weeks for yarns and 6 months for small ropes) and a relative stability in abiotic conditions. Additionally, the fibres show rapid bio-assimilation rates. The rope construction is demonstrated to have a significant impact on the degradation kinetics, suggesting possible strategies to enhance durability. The results indicate that these rayon fibre ropes may offer an attractive alternative to synthetic fibre ropes to reduce impact where there is a high risk of rope loss at sea.

Isolation of marine bacteria with potential for polyhydroxyalkanoate degradation and optimization for enzyme production

Plastic materials are widely used because of their strength, light weight, durability, and environmental resistance. However, their decomposition rates are significantly slower than their typical lifespans. The rapid and continuous increase in plastic consumption has caused severe environmental impacts due to the accumulation of plastic waste. We identified potential polyhydroxyalkanoate (PHA)-degrading bacteria from marine environments capable of producing extracellular PHA depolymerases crucial for biodegrading PHAs. Marine debris was collected to screen poly [(R)-3-hydroxybutyric acid] (P(3HB))-degrading bacteria. Six isolates showed the ability to produce clear zones surrounding their colonies by degrading the bioplastic P(3HB). The isolate SS1-2, exhibiting the greatest degradation index of 1.44, was chosen for optimization through the statistical technique. The results indicated that NH4Cl was the best nitrogen source for enzyme production, and the response surface methodology (RSM) suggested that the greatest P(3HB) depolymerase production could be achieved when the concentrations of substrate loading and NH4Cl both set at 0.5%. Analysis of the 16S rRNA sequence of isolate SS1-2 revealed similarity to Pseudooceanicola antarcticus CGMCC 1.12662 (97.81% similarity). The findings of this study indicate the potential for further exploitation of this depolymerase in enzyme kinetics studies and its application in PHA degradation experiments.

Environmentally ion-dissociable high-performance supramolecular polyelectrolyte plastics

Robust and stiff polymeric materials usually rely on dense covalent crosslinking, which endows them with excellent properties such as high durability and outstanding thermal stability. However, because of the strong covalent bonds within the network, these polymeric materials are not easily degraded or recycled, giving rise to uncontrolled accumulation of end-of-life plastics in seawater or soil. Here, we present a general strategy to fabricate high-performance supramolecular polyelectrolyte plastics with environmentally ion-dissociable properties in a facile manner. By combining dynamic supramolecular hydrogen bonding and multiple electrostatic crosslinking with hydrophobic interactions, the resulting stable supramolecular polyelectrolyte plastic possesses a tensile strength of 93.6 ± 3.3 MPa and a Young's modulus of 2.3 ± 0.3 GPa, outperforming most of the commercial plastics. More importantly, the unique supramolecular dynamic network structures endow the polyelectrolyte plastics with excellent remoldability, good recyclability, and efficient dissociation in seawater and soil under ambient conditions. The simple fabrication strategy developed herein for robust sustainable polyelectrolyte plastics appears to be applicable to other bio-sourced and synthetic polyelectrolytes. This work provides a practical way for fabricating sustainable high-performance plastics by elegantly designing the supramolecular networks of polyelectrolytes.

Plastics of the Future? An Interdisciplinary Review on Biobased and Biodegradable Polymers: Progress in Chemistry, Societal Views, and Environmental Implications

Global demand to reduce polymer waste and microplastics pollution has increased in recent years, prompting further research, development, and wider use of biodegradable and biobased polymers (BBPs). BBPs have emerged as promising alternatives to conventional plastics, with the potential to mitigate the environmental burdens of persistent plastic waste. We provide an updated perspective on their impact, five years after our last article, featuring several recent advances, particularly in exploring broader variety of feedstock, applying novel chemical modifications, and developing new functionalities. Life-cycle assessments reveal that environmental performance of BBPs depends on several factors including feedstock selection, production efficiency, and end-of-life management. Furthermore, the introduction of BBPs in several everyday life products has also influenced consumer perception, market dynamics, and regulatory frameworks. Although offering environmental advantages in specific applications, BBPs also raise concerns regarding their biodegradability under varying environmental conditions, potential microplastic generation, and soil health impacts. We highlight the need for a circular approach considering the entire polymer life cycle, from feedstock sourcing, modification and use, to end-of-life options. Interdisciplinary research, collaborative initiatives, and informed policymaking are crucial to unlocking the full potential of BBPs and exploiting their contribution to create a circular economy and more sustainable future.

Native polymer degradation capacity of microorganisms in agricultural soils

With a growing global population increasing demand for food production, fertilisers are of paramount importance in the agricultural industry. New fertiliser coating candidates may reduce environmental harm but it is critical that they are evaluated for their native biodegradation potential within agricultural soils and their effects on microbial communities. Four of the seven compounds tested, poly(1,4-butylene adipate) (PBA), polyethylene adipate (PEA), polycaprolactone (PCL) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), showed degradation by indigenous soil microorganisms with headspace CO2 concentrations increasing between 14 to 98 % compared to the soil only control. Surprisingly, two previously characterised biodegradable polymers, polyethylene succinate (PES) and poly(1,4-butylene succinate) (PBS), showed minimal biodegradation in our study. Polymer degradation was confirmed visually using scanning electron microscopy and occurred in conjunction with shifts in the bacterial and fungal community composition of the soils. Soils with PBA, PEA, PCL and PHBV were enriched with polymer degrading microorganisms, such as Streptomyces spp., Bacillus spp., Exophiala spp. and Talaromyces spp. Using whole soil microcosms under ambient conditions to investigate indigenous degradation potential of polymers for fertiliser coatings provides an initial holistic picture of their degradation potential compared with using axenic cultures alone, and provides crucial new insights into the future of eco-friendly controlled release fertilisers.

Development of Marine-Degradable Poly(Ester Amide)s with Strong, Up-Scalable, and Up-Cyclable Performance

Biodegradable polyesters provide an attractive alternative to non-degradable plastics but often encounter a tradeoff between biodegradability and mechanical properties because esters are rotational and lack hydrogen bonds. Conversely, natural polyamides, i.e., silk exhibit excellent mechanical strength because amides are non-rotational and form hydrogen bonds. Unlike esters, the nitrogen in amides can enhance microbial biodegradation. However, protein engineering exhibits limited productivity, and artificial polyamides, i.e., nylon remain non-degradable due to their hydrophobic nature. Herein, a method is proposed for developing poly(ester amide)s (PEA)s, a polyester and polyamide hybrid, to address prevailing production challenges. These materials are synthesized from upcycled monomers in a 10 L reactor and converted into films and yarns. They achieve a tensile strength of 109 MPa and tenacity of 5.0 g de-1, while withstanding ironing temperatures. They achieve a remarkable 92% marine biodegradability in 12 months, which is rarely attained by current bioplastics, and exhibit low environmental impact in terms of greenhouse gas emissions. While biodegradable polyesters have remained within the performance range of commodity plastics, PEAs fall into the high-performance category, potentially reaching markets that existing biodegradable plastics have not, such as fishing lines and clothing.

Exploring the intricate studies on low-density polyethylene (LDPE) biodegradation by Bacillus cereus AP-01, isolated from the gut of Styrofoam-fed Tenebrio molitor larvae

This study aims to investigate the biodegradation potential of a gut bacterial strain, Bacillus cereus AP-01, isolated from Tenebrio molitor larvae fed Styrofoam, focusing on its efficacy in degrading low-density polyethylene (LDPE). The biodegradation process was evaluated through a series of assays, including clear zone assays, biodegradation assays, and planktonic cell growth assessments in mineral salt medium (MSM) over a 28-day incubation period. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to characterize the alterations in LDPE pellets, followed by molecular characterization. Over three months, sterile soil + LDPE pellets were treated with different concentrations of gut bacterial strain. The degradation capabilities were assessed by measuring pH, total microbial counts, carbon dioxide evolution, weight loss, and conducting phase contrast microscopy and mechanical strength tests. Results demonstrated that MSM containing LDPE as a carbon source with gut bacterial strain produced a clear zone and enhanced planktonic cell growth. FTIR analysis revealed the formation of new functional groups in the LDPE, while SEM images displayed surface erosion and cracking, providing visual evidence of biodegradation. Molecular characterization confirmed the strain as Bacillus cereus AP-01 (NCBI Accession Number: OR288218.1). A 10% inoculum concentration of Bacillus cereus AP-01 exhibited increased soil bacterial counts, carbon dioxide evolution, and pH levels, alongside a notable weight loss of 30.3% in LDPE pellets. Mechanical strength assessments indicated substantial reductions in tensile strength (7.81 ± 0.84 MPa), compression (4.92 ± 0.53 MPa), hardness (51.96 ± 5.62 shore D), flexibility (10.62 ± 1.15 MPa), and impact resistance (14.79 ± 0.94 J). These findings underscore the biodegradation potential of Bacillus cereus AP-01, presenting a promising strategy for addressing the global LDPE pollution crisis.

Degradable poly(β-amino ester) microparticles for cleansing products and food fortification

Microplastic pollution is a pressing global crisis caused by the extensive use of nondegradable microplastic materials in daily activities. One effective approach to mitigate this issue is to replace nondegradable plastics with degradable materials that have properties amendable for targeted applications. Here we present the development of a degradable microparticle (MP) platform based on a poly(β-amino ester) (PAE) that degrades into sugar and amino acid derivatives. This PAE MP platform showed functional replacement of nondegradable microplastics used in cleansing products and food fortification. In cleansing products, PAE MPs effectively enhanced the cleansing efficiency of a representative rinse-off product and showed effective removal of potentially toxic elements, as an alternative of traditional nondegradable microbeads. In food fortification, PAE MPs provided robust protection for multiple essential vitamins and minerals against extensive cooking and storage conditions with rapid nutrient release in a simulated human digestion system. Collectively, these PAE MPs present a potential platform to replace microplastic usage on a global scale in many applications.

Sericin coats of silk fibres, a degumming waste or future material?

Silk is a fibrous biopolymer with a recorded history in the textile industries for centuries. This fibre is constituted of two different proteins: fibroin and sericin, of which the latter accounting for approximately 20-30 % of the silk mass. Silk sericin (SSER) was previously considered as a waste by-product in silk fibroin extraction. SSER has recently garnered significant scientific interest due to its extensive biological and pharmacological properties. These include antioxidant effects, biocompatibility, low immunogenicity, controlled biodegradability, and the ability to induce cell proliferation. This review covers studies about various aspects of this emerging material, namely, its general morphology, specific structure, molecular weight, features of different layers, and gene sequences. The impact of different extraction methods and the application of extracted SSER based on molecular weight are discussed. Additionally, the characteristic functional groups in the amino acids of sericin facilitate its applications in regenerative medicine, wound healing, drug delivery, textile, environment, and energy, in various forms like hydrogels, films, scaffolds, and conduits. SSER-based materials offer great potentials for multi-functional applications in the upcoming decades, showcasing adaptability for various functional uses and promising future technological advancements.

Tuning Biodegradation of Poly (lactic acid) (PLA) at Mild Temperature by Blending with Poly (butylene succinate-co-adipate) (PBSA) or Polycaprolactone (PCL)

Biobased plastics are fully or partially made from biological resources but are not necessarily biodegradable or compostable. Poly (lactic acid) (PLA), one of the most diffused bioplastics, is compostable in industrial environments, but improving degradation in home composting conditions, in soil and in seawater could be beneficial for improving its end of life and general degradability. Blends obtained by the extrusion of PLA with different amounts of poly (butylene succinate-co-adipate) (PBSA) or poly (caprolactone) (PCL) were characterized in terms of their home composting, soil, marine and freshwater biodegradation. The blending strategy was found to be successful in improving the home compostability and soil compostability of PLA. Thanks to the correlations with morphological characterization as determined by electron microscopy, it was possible to show that attaining an almost co-continuous phase distribution, depending on the composition and melt viscosity of the blend components, can enhance PLA degradation in home composting conditions. Tests in marine and freshwater were also performed, and the obtained results showed that in marine conditions, pure PLA is degradable. A comparison of different tests evidenced that salt dissolved in marine water plays an important role in favoring PLA's degradability.

Prevention policies for the marine ecological environment in the South China Sea as a consequence of excessive plastic compound use in Vietnam

Vietnam suffers from a distressing predicament: It ranks among the most heavily contaminated nations on earth. Its coastal and marine domains are plagued by an excess of plastic waste. Vietnam has consistently discharged a substantial amount of waste into the oceans, ranging from 0.28 to 0.73 million metric tons annually. Numerous areas have emerged as focal points of plastic pollution throughout its extensive seashore and marine areas. The escalating presence of marine litter poses an increasingly grave threat to the intricate equilibrium of Vietnam's marine ecosystems. This comprehensive policy study reveals that the mounting problem of ocean plastic pollution, characterized by the abundance of floating plastic debris, imperils both plant and animal life, placing various marine species such as seabirds, fish, turtles, and cetaceans at risk. The consumption of minuscule plastic particles and the harmful impact of chemical pollutants from plastic waste in the ocean not only endangers the vitality of marine life but also poses a substantial hazard to human well-being because plastic waste infiltrates the food chain. This research reveals that, despite the existence of numerous laws and policies-including the Law on Environmental Protection 2020, the Marine Plastic Waste Management Initiative for the Fisheries Sector 2020-2030, and the National Action Plan for Management of Marine Plastic Litter-a significant amount of plastic waste is infiltrating the river network and eventually infiltrating oceans as a result of improper monitoring and ineffective enforcement of these legislations. Relying primarily on existing data released by the government and other sources and a wide range of gray literature retrieved from reputable databases, this study aims to evaluate the role of Vietnam's legal framework for combating the critical issue of marine plastic pollution in the South China Sea. Integr Environ Assess Manag 2024;20:2088-2106. © 2024 SETAC.

Correlation of Enzymatic Depolymerization Rates with the Structure of Polyethylene-Like Long-Chain Aliphatic Polyesters

Long-chain aliphatic polyesters are emerging sustainable materials that exhibit polyethylene-like properties while being amenable to chemical recycling and biodegradation. However, varying polyester chemical structures results in markedly different degradation rates, which cannot be predicted from commonly correlated bulk polyester properties, such as polymer melting temperature. To elucidate these structure-degradability relationships, long-chain polyesters varying in their monomer composition and crystallinity were subjected to enzymatic hydrolysis, the rates of which were quantified via detection of formed monomers. Copolymers with poorly water-soluble, long-chain diol monomers (e.g., 1,18-octadecanediol) demonstrated strongly reduced depolymerization rates compared to copolymers with shorter chain length diol monomers. This was illustrated by, e.g., the 20× faster hydrolysis of PE-4,18, consisting of 1,4-butanediol and 1,18-octadecanedicarboxylic acid monomers, relative to PE-18,4. The insoluble long-chain diol monomer released upon hydrolysis was proposed to remain attached to the bulk polymer surface, decreasing the accessibility of the remaining ester bonds to enzymes for further hydrolysis. Tuning of polyester crystallinity via the introduction of branched monomers led to variable hydrolysis rates, which increased by an order of magnitude when crystallinity decreased from 72% to 45%. The results reported enables the informed design of polyester structures with balanced material properties and amenability to depolymerization.

Reinforcement and Controlling the Stability of Poly(ε-caprolactone)-Based Polymeric Materials via Reversible and Movable Cross-Links Employing Cyclic Polyphenylene Sulfide

Due to its biodegradation ability, poly(ε-caprolactone) (PCL) is a suitable alternative for packaging materials; however, its biodegradation can also lead to instability in its usage. Cyclic polyphenylene sulfide (7U) has been shown to form rotaxane structures with PCL by simple blending to generate the π-π stacking effect and movable cross-link. A 2-fold increase in toughness and no decrease in Young's modulus for the PCL-based polyurethane with 7U are observed. The rotaxane structures mainly exist in the amorphous regions and have no impact on the crystallinity of PCL. Under the catalysis of lipase in aqueous solution, the stability of PCL is improved due to the 7U's suppression of the attack from the enzymes on PCL. After dissolution of the PCL films in the organic solvent, the dispersion of 7U and the breakage of the cross-links lead to little suppression on degradation during the catalysis of lipase. Thus, the controlled stability of PCL using 7U can prolong the life span of the biodegraded PCL materials.

Porphyrin as Photosensitizers for Controlling Marine Biodegradation of Polymer Composites

Biodegradable polymer-photosensitizer composites were developed, which is suppressed biodegradation due to bactericidal activity under light irradiation but proceeds under dark conditions. The composites exhibited antibacterial activity under light irradiation, which was attributed to the generation of singlet oxygen (1O2). Biodegradation was evaluated in seawater using the biochemical oxygen demand (BOD) method. In the dark, the composite and base polymer biodegraded to a similar degree. However, under light irradiation, the biodegradation of the composite was suppressed. In field tests, the rate of volume reduction of the composites decreased under illumination. The main cause of the suppression of biodegradation is suggested to be due to the decrease in the number of bacteria on the surface of the material and the inactivation of exoenzymes. The findings are expected to contribute to the development of biodegradable polymers that do not biodegrade during use but only when disposed of in the environment, thereby achieving on-demand degradation.

Development of a Fast and Efficient Strategy Based on Nanomagnetic Materials to Remove Polystyrene Spheres from the Aquatic Environment

Microplastics contamination is growing globally, being a risk for different environmental compartments including animals and humans. At present, some Spanish beaches and coasts have been affected by discharges of these pollutants, which have caused a serious environmental problem. Therefore, efficient strategies to remove microplastics (MPs) from environmental samples are needed. In this study, the application of three magnetic materials, namely iron oxide (Fe3O4) and the composites Fe3O4@Ag and Fe3O4@Ag@L-Cysteine, to remove MPs, specifically polystyrene (PS), from water samples has been assessed. The magnetic nanoparticles were synthesized and characterized by field effect scanning electron microscopy with energy dispersive X-ray spectroscopy detection (FESEM-EDX). Experimental conditions such as temperature, time, and pH during the removal process were assessed for the different adsorbent materials. The removal rate was calculated by filtering the treated water samples and counting the remaining MPs in the water using ImageJ software. The strongest removal efficiency (100%) was shown using Fe3O4@Ag@L-Cysteine for PS at 50 mg L-1 within 15 min of the separation process at room temperature and a neutral pH. A thermodynamic study demonstrated that the developed MPs elimination strategy was a spontaneous and physisorption process. Coated Fe3O4 magnetic nanoparticles were demonstrated to be an efficient adsorbent for MP removal in aquatic environments and their use a promising technique for the control of MPs contamination.

UV-Mediated Facile Fabrication of a Robust, Fully Renewable and Controllably Biodegradable Poly(lactic acid)-Based Covalent Adaptable Network

A robust and fully biobased covalent adaptable network (CAN) that allows recyclability, biocompatibility, and controlled biodegradability is reported. The CAN was fabricated through a simple photo-cross-linking method, wherein low-molecular-weight poly(lactic acid) (∼3 kDa) was modified with end 1,2-dithiolane rings through a one-step Steglich esterification reaction with thioctic acid (TA). These incorporated 1,2-dithiolane rings undergo photoinduced ring-opening polymerization, thus enabling the cross-linking of poly(lactic acid) with abundant dynamic disulfide bonds. The resultant CAN demonstrates excellent transparency, effective UV-blocking capabilities below 320 nm, robust tensile strength (∼39 MPa), and superior dimensional stability at 80 °C, alongside attractive biocompatibility. Moreover, owing to the dynamic exchange and redox-responsiveness of disulfide bonds, the material can be recycled by hot-pressing and a reduction-oxidation process while also being capable of controllably biodegrading at the end of its lifecycle. Furthermore, it exhibits reconfigurable shape memory properties with fast recovery. This study elucidates a straightforward approach to fabricating multifunctional and sustainable polymer materials with potential applications in diverse fields such as packaging, coating, and biomedicine.

Degradation of a Wholly Aromatic Main-Chain Thermotropic Liquid-Crystalline Polymer Mediated by Superbases

Plastic circular economy needs to be established to solve environmental issues related to plastic waste. Superengineering plastics such as liquid-crystalline (LC) polymers exhibit excellent thermal and mechanical properties, resulting in poor degradability in natural environment. Herein, we report the degradation of a wholly aromatic thermotropic LC polyester, poly(4-hydroxybenzoic acid-co-6-hydroxy-2-naphthoic acid) (Vectra) mediated by superbases. Methanolysis and hydrolysis of Vectra yield its monomeric compounds, 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and their methyl esters. Among several transesterification catalysts explored, 1,5,7-triazabicylco[4.4.0]dec-5-ene (TBD) is the most suitable for the methanolysis of Vectra. The complete degradation of Vectra is achieved under reflux. The degradation proceeds heterogeneously via a surface erosion mechanism, preferentially starting from less chain-packed regions. Model reactions using aryl arylates reveal that monomeric compound-superbase complexes could mediate the cleavage of the ester bonds in both homogeneous and heterogeneous systems. The ester bonds of Vectra have inherent poor reactivity and are protected by oriented robust structures of the polymer. Nevertheless, the superbases enable the degradation of Vectra via the cleavage of the ester bonds by methanol. These outcomes open the way for recycling high-performance plastics as well as demonstrate the feasibility of recovering precious aromatic compounds from plastic waste as aromatic feedstock.

Mechanochemical Backbone Editing for Controlled Degradation of Vinyl Polymers

The chemically inert nature of fully saturated hydrocarbon backbones endows vinyl polymers with desirable durability, but it also leads to their significant environmental persistence. Enhancing the sustainability of these materials requires a pivotal yet challenging shift: transforming the inert backbone into one that is degradable. Here, we present a versatile platform for mechanochemically editing the fully saturated backbone of vinyl polymers towards degradable polymer chains by integrating cyclobutene-fused succinimide (CBS) units along backbone through photo-iniferter reversible addition-fragmentation chain-transfer (RAFT) copolymerization. Significantly, the evenly insertion of CBS units does not compromise thermal or chemical stability but rather offers a means to adjust the properties of polymethylacrylate (PMA). Meanwhile, reactive acyclic imide units can be selectively introduced to the backbone through mechanochemical activation (pulse ultrasonication or ball-milling grinding) when required. Subsequent hydrolysis of the acyclic imide groups enables efficient degradation, yielding telechelic oligomers. This approach holds promise for inspiring the design and modification of more environmentally friendly vinyl polymers through backbone editing.

Reprogrammable, Sustainable, and 3D-Printable Cellulose Hydroplastic

Modern human societies are highly dependent on plastic materials, however, the bulk of them are non-renewable commodity plastics that cause pollution problems and consume large amounts of energy for their thermal processing activities. In this article, a sustainable cellulose hydroplastic material and its composites, that can be shaped repeatedly into various 2D/3D geometries using just water are introduced. In the wet state, their high flexibility and ductility make it conducive for the shaping to take place. In the ambient environment, the wet hydroplastic transits spontaneously into rigid materials with its intended shape in a short time of <30 min despite a thickness of hundreds of microns. They also possess humidity resistance and are structurally stable in highly humid environments. Given their excellent mechanical properties, geometry reprogrammability, bio-based, and biodegradable nature, cellulose hydroplastic poses as a sustainable alternative to traditional plastic materials and even "green" thermoplastics. This article also demonstrates the possibility of 3D-printing these hydroplastics and the potential of employing them in electronics applications. The demonstrated hydroshapable structural electronic components show capability in performing electronic functions, load-bearing ability and geometry versatility, which are attractive features for lightweight, customizable and geometry-unique electronic devices.

Fully Bio-Based 2,5-Furandicarboxylic Acid Polyester toward Plastics with Mechanically Robust, Excellent Gas Barrier and Fast Degradation

Aliphatic-aromatic copolyesters offer a promising solution to mitigate plastic pollution, but high content of aliphatic units (>40 %) often suffer from diminished comprehensive performances. Poly(butylene oxalate-co-furandicarboxylate) (PBOF) copolyesters were synthesized by precisely controlling the oxalic acid content from 10 % to 60 %. Compared with commercial PBAT, the barrier properties of PBOF for H2O and O2 increased by more than 6 and 26 times, respectively. The introduction of the oxalic acid units allowed the water contact angle to be reduced from 82.5° to 62.9°. Superior hydrophilicity gave PBOF an excellent degradation performance within a 35-day hydrolysis. Interestingly, PBO20F and PBO30F also displayed obvious decrease of molecular weight during hydrolysis, with elastic modulus >1 GPa and tensile strength between 35-54 MPa. PBOF achieved the highest hydrolysis rates among the reported PBF-based copolyesters. The hydrolytic mechanism was further explored based on Fukui function analysis and density functional theory (DFT) calculation. Noncovalent analysis indicated that the water molecules formed hydrogen bonding interaction with adjacent ester groups and thus improved the reactivity of carbonyl carbon. PBOF not only meet the requirements of the high-performance packaging market but can quickly degrade after the end of their usage cycles, providing a new choice for green and environmental protection.

Designed to Degrade: Tailoring Polyesters for Circularity

A powerful toolbox is needed to turn the linear plastic economy into circular. Development of materials designed for mechanical recycling, chemical recycling, and/or biodegradation in targeted end-of-life environment are all necessary puzzle pieces in this process. Polyesters, with reversible ester bonds, are already forerunners in plastic circularity: poly(ethylene terephthalate) (PET) is the most recycled plastic material suitable for mechanical and chemical recycling, while common aliphatic polyesters are biodegradable under favorable conditions, such as industrial compost. However, this circular design needs to be further tailored for different end-of-life options to enable chemical recycling under greener conditions and/or rapid enough biodegradation even under less favorable environmental conditions. Here, we discuss molecular design of the polyester chain targeting enhancement of circularity by incorporation of more easily hydrolyzable ester bonds, additional dynamic bonds, or degradation catalyzing functional groups as part of the polyester chain. The utilization of polyester circularity to design replacement materials for current volume plastics is also reviewed as well as embedment of green catalysts, such as enzymes in biodegradable polyester matrices to facilitate the degradation process.

Effects of Molecular Weight on the Marine Biodegradability of Poly(l-lactic acid)

Poly(l-lactic acid) (PLA) is a biodegradable bioplastic with limited marine degradation. This study examines the impact of molecular weight on PLA's marine biodegradability. We synthesized PLA with terminal hydroxyl groups (PLA-OH) with degrees of polymerization (DP) between 14 and 642 and conducted biochemical oxygen demand (BOD) tests. Samples with a DP of 422 or 642 did not degrade, like commercial PLA. However, PLA-OH with a DP below 314 showed biodegradability, with DP 14 exhibiting a higher degradability than cellulose. Size exclusion chromatography (SEC) confirmed a decrease in molecular weight for samples with DPs below 314, indicating extracellular microbial activity. These findings suggest that PLA-OH with a DP under 314 can be degraded in marine conditions, unlike high-molecular-weight PLA. If the DP of high-molecular-weight PLA can be reduced to 314 by some specific method, then it is expected that PLA can be used to create marine biodegradable materials.

Mechanically triggered on-demand degradation of polymers synthesized by radical polymerizations

Polymers that degrade on demand have the potential to facilitate chemical recycling, reduce environmental pollution and are useful in implant immolation, drug delivery or as adhesives that debond on demand. However, polymers made by radical polymerization, which feature all carbon-bond backbones and constitute the most important class of polymers, have proven difficult to render degradable. Here we report cyclobutene-based monomers that can be co-polymerized with conventional monomers and impart the resulting polymers with mechanically triggered degradability. The cyclobutene residues act as mechanophores and can undergo a mechanically triggered ring-opening reaction, which causes a rearrangement that renders the polymer chains cleavable by hydrolysis under basic conditions. These cyclobutene-based monomers are broadly applicable in free radical and controlled radical polymerizations, introduce functional groups into the backbone of polymers and allow the mechanically gated degradation of high-molecular-weight materials or cross-linked polymer networks into low-molecular-weight species.

Microplastics Biodegradation by Estuarine and Landfill Microbiomes

Plastic pollution poses a worldwide environmental challenge, affecting wildlife and human health. Assessing the biodegradation capabilities of natural microbiomes in environments contaminated with microplastics is crucial for mitigating the effects of plastic pollution. In this work, we evaluated the potential of landfill leachate (LL) and estuarine sediments (ES) to biodegrade polyethylene (PE), polyethylene terephthalate (PET), and polycaprolactone (PCL), under aerobic, anaerobic, thermophilic, and mesophilic conditions. PCL underwent extensive aerobic biodegradation with LL (99 ± 7%) and ES (78 ± 3%) within 50-60 days. Under anaerobic conditions, LL degraded 87 ± 19% of PCL in 60 days, whereas ES showed minimal biodegradation (3 ± 0.3%). PE and PET showed no notable degradation. Metataxonomics results (16S rRNA sequencing) revealed the presence of highly abundant thermophilic microorganisms assigned to Coprothermobacter sp. (6.8% and 28% relative abundance in anaerobic and aerobic incubations, respectively). Coprothermobacter spp. contain genes encoding two enzymes, an esterase and a thermostable monoacylglycerol lipase, that can potentially catalyze PCL hydrolysis. These results suggest that Coprothermobacter sp. may be pivotal in landfill leachate microbiomes for thermophilic PCL biodegradation across varying conditions. The anaerobic microbial community was dominated by hydrogenotrophic methanogens assigned to Methanothermobacter sp. (21%), pointing at possible syntrophic interactions with Coprothermobacter sp. (a H2-producer) during PCL biodegradation. In the aerobic experiments, fungi dominated the eukaryotic microbial community (e.g., Exophiala (41%), Penicillium (17%), and Mucor (18%)), suggesting that aerobic PCL biodegradation by LL involves collaboration between fungi and bacteria. Our findings bring insights on the microbial communities and microbial interactions mediating plastic biodegradation, offering valuable perspectives for plastic pollution mitigation.

Enhanced Marine Biodegradation of Polycaprolactone through Incorporation of Mucus Bubble Powder from Violet Sea Snail as Protein Fillers

Microplastics' spreading in the ocean is currently causing significant damage to organisms and ecosystems around the world. To address this oceanic issue, there is a current focus on marine degradable plastics. Polycaprolactone (PCL) is a marine degradable plastic that is attracting attention. To further improve the biodegradability of PCL, we selected a completely new protein that has not been used before as a functional filler to incorporate it into PCL, aiming to develop an environmentally friendly biocomposite material. This novel protein is derived from the mucus bubbles of the violet sea snail (VSS, Janthina globosa), which is a strong bio-derived material that is 100% degradable in the sea environment by microorganisms. Two types of PCL/bubble composites, PCL/b1 and PCL/b5, were prepared with mass ratios of PCL to bubble powder of 99:1 and 95:5, respectively. We investigated the thermal properties, mechanical properties, biodegradability, surface structure, and crystal structure of the developed PCL/bubble composites. The maximum biochemical oxygen demand (BOD) degradation for PCL/b5 reached 96%, 1.74 times that of pure PCL (≈55%), clearly indicating that the addition of protein fillers significantly enhanced the biodegradability of PCL. The surface morphology observation results through scanning electron microscopy (SEM) definitely confirmed the occurrence of degradation, and it was found that PCL/b5 underwent more significant degradation compared to pure PCL. The water contact angle measurement results exhibited that all sheets were hydrophobic (water contact angle > 90°) before the BOD test and showed the changes in surface structure after the BOD test due to the newly generated indentations on the surface, which led to an increase in surface toughness and, consequently, an increase in surface hydrophobility. A crystal structure analysis by wide-angle X-ray scattering (WAXS) discovered that the amorphous regions were decomposed first during the BOD test, and more amorphous regions were decomposed in PCL/b5 than in PCL, owing to the addition of the bubble protein fillers from the VSS. The differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA) results suggested that the addition of mucus bubble protein fillers had only a slight impact on the thermal properties of PCL. In terms of mechanical properties, compared to pure PCL, the mucus-bubble-filler-added composites PCL/b1 and PCL/b5 exhibited slightly decreased values. Although the biodegradability of PCL was significantly improved by adding the protein fillers from mucus bubbles of the VSS, enhancing the mechanical properties at the same time poses the next challenging issue.

Chemically Recyclable and Biodegradable Vulcanized Rubber

The cross-linked nature of vulcanized rubbers as used in tire and many other applications prohibits an effective closed-loop mechanical or chemical recycling. Moreover, vulcanization significantly retards the material's biodegradation. Here, we report a recyclable and biodegradable rubber that is generated by the vulcanization of amorphous, unsaturated polyesters. The elastic material can be broken down via solvolysis into the underlying monomers. After removal of the vulcanized repeat units, the saturated monomers, constituting the major share of the material, can be recovered in overall recycling rates exceeding 90%. Respirometric biodegradation experiments by 13CO2 tracking under environmental conditions via the polyesters' diol monomer indicated depolymerization and partial mineralization of the vulcanized polyester rubbers.

Effects of poly(3-hydroxybutyrate) [P(3HB)] coating on the bacterial communities of artificial structures

The expanding urbanization of coastal areas has led to increased ocean sprawl, which has had both physical and chemical adverse effects on marine and coastal ecosystems. To maintain the health and functionality of these ecosystems, it is imperative to develop effective solutions. One such solution involves the use of biodegradable polymers as bioactive coatings to enhance the bioreceptivity of marine and coastal infrastructures. Our study aimed to explore two main objectives: (1) investigate PHA-degrading bacteria on polymer-coated surfaces and in surrounding seawater, and (2) comparing biofilm colonization between surfaces with and without the polymer coating. We applied poly(3-hydroxybutyrate) [P(3HB)) coatings on concrete surfaces at concentrations of 1% and 6% w/v, with varying numbers of coating cycles (1, 3, and 6). Our findings revealed that the addition of P(3HB) indeed promoted accelerated biofilm growth on the coated surfaces, resulting in an occupied area approximately 50% to 100% larger than that observed in the negative control. This indicates a remarkable enhancement, with the biofilm expanding at a rate roughly 1.5 to 2 times faster than the untreated surfaces. We observed noteworthy distinctions in biofilm growth patterns based on varying concentration and number of coating cycles. Interestingly, treatments with low concentration and high coating cycles exhibited comparable biofilm enhancements to those with high concentrations and low coating cycles. Further investigation into the bacterial communities responsible for the degradation of P(3HB) coatings identified mostly common and widespread strains but found no relation between the concentration and coating cycles. Nevertheless, this microbial degradation process was found to be highly efficient, manifesting noticeable effects within a single month. While these initial findings are promising, it's essential to conduct tests under natural conditions to validate the applicability of this approach. Nonetheless, our study represents a novel and bio-based ecological engineering strategy for enhancing the bioreceptivity of marine and coastal structures.

Metagenomic investigations into the microbial consortia, degradation pathways, and enzyme systems involved in the biodegradation of plastics in a tropical lentic pond sediment

The exploitation of exciting features of plastics for diverse applications has resulted in significant plastic waste generation, which negatively impacts environmental compartments, metabolic processes, and the well-being of aquatic ecosystems biota. A shotgun metagenomic approach was deployed to investigate the microbial consortia, degradation pathways, and enzyme systems involved in the degradation of plastics in a tropical lentic pond sediment (APS). Functional annotation of the APS proteome (ORFs) using the PlasticDB database revealed annotation of 1015 proteins of enzymes such as depolymerase, esterase, lipase, hydrolase, nitrobenzylesterase, chitinase, carboxylesterase, polyesterase, oxidoreductase, polyamidase, PETase, MHETase, laccase, alkane monooxygenase, among others involved in the depolymerization of the plastic polymers. It also revealed that polyethylene glycol (PEG), polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polyethylene terephthalate (PET), and nylon have the highest number of annotated enzymes. Further annotation using the KEGG GhostKOALA revealed that except for terephthalate, all the other degradation products of the plastic polymers depolymerization such as glyoxylate, adipate, succinate, 1,4-butanediol, ethylene glycol, lactate, and acetaldehyde were further metabolized to intermediates of the tricarboxylic acid cycle. Taxonomic characterization of the annotated proteins using the AAI Profiler and BLASTP revealed that Pseudomonadota members dominate most plastic types, followed by Actinomycetota and Acidobacteriota. The study reveals novel plastic degraders from diverse phyla hitherto not reported to be involved in plastic degradation. This suggests that plastic pollution in aquatic environments is prevalent with well-adapted degrading communities and could be the silver lining in mitigating the impacts of plastic pollution in aquatic environments.

Water-Degradable Oxygen-Rich Polymers with AB/ABB Units from Fast and Selective Copolymerization

Researchers have been chasing plastics that can automatically and fully degrade into valuable products under natural conditions. Here, we develop a series of water-degradable polymers from the first reported fast and selective cationic copolymerization of formaldehyde (B) with cyclic anhydrides (A). In addition to readily accessible monomers, the method is performed at industrially relevant temperatures (~100 °C), takes tens or even minutes, and uses common acid as the catalyst. Interestingly, such polymers possess tunable AB/ABB-type repeating units, which are considered to be thermodynamic and kinetic products, respectively, resulting in low carbon content ([O] : [C] up to 1 : 1). Notably, the polymers can completely degrade to valuable diacids within 150 days in water at ambient temperature owing to the incorporation of carboxyl terminals and acid-responsive acetal units. By washing with aqueous sodium carbonate, the polymers are relatively stable over several months.

Synthesis and Deconstruction of Polyethylene-type Materials

Polyethylene deconstruction to reusable smaller molecules is hindered by the chemical inertness of its hydrocarbon chains. Pyrolysis and related approaches commonly require high temperatures, are energy-intensive, and yield mixtures of multiple classes of compounds. Selective cleavage reactions under mild conditions ( Collapse

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MESH Headings Collapse

Grants

• H2020 European Research Council

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Affiliation(s)

Simon T. Schwab Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
Maximilian Baur Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
Taylor F. Nelson Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
Stefan Mecking Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany

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Biodegradable reactive compatibilizers for efficient in-situ compatibilization of poly (lactic acid)/poly (butylene adipate-terephthalate) blends

The wide application of fully biodegradable polylactic acid/polybutylene terephthalate (PLA/PBAT) blends in environmentally friendly packaging were limited because of poor compatibility. Normal compatibilizers suffer from poor thermal stability and non-biodegradability. In this work, epoxy copolymer (MDOG) with different molecular structures were made of 2-methylene-1, 3-dioxoheptane, and glycidyl methacrylate as raw materials by free radical copolymerization. MDOG copolymers have good biodegradability and a high thermal decomposition temperature of 361 °C. The chemical reaction of the epoxy groups in MDOG with PLA and PBAT during the melting reaction improved the interfacial bonding by decreasing the particle size of PBAT. Compared to the PLA/PBAT blends, the tensile strength and fracture toughness of PLA/PBAT/MDOG blends were enhanced to 34.6 MPa and 115.8 MJ/m3, which are 25 % and 81 % higher, respectively. As a result, this work offers new methods for developing thermally stable and biodegradable compatibilizers, which will hopefully promote the development of packaging industry.

Effect of oxygen-containing functional groups on the micromechanical behavior of biodegradable plastics and their formation of microplastics during aging

Biodegradable plastics (BPs) are more prone to generate harmful microplastics (MPs) in a short time, which have always been ignored. Oxygenated functional group formation is considered to be a key indicator for assessing microplastic formation, while it is difficult to characterize at a very early stage. The micromechanical properties of the aging plastic during the formation of the MPs are highly influenced by the evolution of oxygen-containing functional groups, however, their relationship has rarely been revealed. Herein, we compared changes in the physicochemical properties of BPs and non-degradable plastic bags during aging in artificial seawater, soil, and air. The results showed that the oxidation of plastics in the air was the most significant, with the most prominent oxidation in BPs. The accumulation of carbonyl groups leads to a significant increase in the micromechanical properties and surface brittleness of the plastic, further exacerbating the formation of MPs. It was also verified by the FTIR, 2D-COS, AFM, and Raman spectroscopy analyses. Furthermore, the increased adhesion and roughness caused by oxygen-containing functional groups suggest that the environmental risks of BPs cannot be ignored. Our findings suggest that the testing of micromechanical properties can predicate the formation of the MPs at an early stage.

Construction of multiple crosslinked networks for the preparation of high-performance lignin-containing cellulose nanofiber reinforced polyvinyl alcohol films

Polyvinyl alcohol (PVA) film, a promising alternative to non-biodegradable plastic packaging films for food and medical packaging, is limited by poor water resistance. In this work, a simple solvent evaporation self-assembly was used to construct a nanophase separation structure to establish dense interfacial hydrogen bonding, covalent bonding and iron metal ion coordination interactions between lignin-containing cellulose nanofibers (LCNFs) and PVA matrix to improve the interfacial force and solve the problem of poor compatibility of LCNFs in PVA. The iron ion (Fe3+) coordination tended to combine with the more active lignin phenolic hydroxyl group to construct the nanophase separation structure. Covalent crosslinking of glutaraldehyde (GA) improved the interfacial compatibility of PVA/LCNF films, enhanced the interfacial bonding and formed a homogeneous structure. The multi-nanophase structures improved the strength and elastic modulus of the PVA/LCNF film and provided the films with extremely low water absorption, water vapor transmission rate and excellent UV-shielding. Compared with pure PVA film, PVA-10L-5Fe-3GA film had about 106.9 % higher tensile strength, 93.9 % lower water absorption and 93.4 % lower mass loss, 69.8 % lower water vapor transmission coefficient, and was able to shield UV at 200-400 nm, which is highly expected to be used in packaging films.

Umpolung Isomerization in Radical Copolymerization of Benzyl Vinyl Ether with Pentafluorophenylacrylate Leading to Degradable AAB Periodic Copolymers

This study revealed that benzyl vinyl ether (BnVE) shows a peculiar isomerization propagation in its radical copolymerization with an electron-deficient acrylate carrying a pentafluorophenyl group (PFA). The co-monomer pair inherently exhibits the cross-over propagation feature due to the large difference in the electron density. However, the radical species of PFA was found to undergo a backward isomerization to the penultimate BnVE pendant giving a benzyl radical species prior to propagation with BnVE. The isomerization brings a drastic change in the character of the growing radical species from electrophilic to nucleophilic, and thus the isomerized benzyl radial species propagates with PFA. Consequently, the two monomers were consumed in the order AAB (A: PFA; B: BnVE) and the unique periodic consumption was confirmed by the pseudo-reactivity ratios calculated by the penultimate model: r11 =0.174 and r21 =6600 for PFA (M1 ) with BnVE (M2 ). The pentafluorophenyl ester groups of the resulting copolymers are transformed into ester and amide groups by post-polymerization alcoholysis and aminolysis modifications. The unique isomerization in the AAB sequence allowed the periodic introduction of a benzyl ether structure in the backbone leading to efficient degradation under acid conditions.

Marine biodegradation of poly[(R)-3-hydroxybutyrate-co-4-hydroxybutyrate] elastic fibers in seawater: dependence of decomposition rate on highly ordered structure

Here, we report the marine degradability of polymers with highly ordered structures in natural environmental water using microbial degradation and biochemical oxygen demand (BOD) tests. Three types of elastic fibers (non-porous as-spun, non-porous drawn, and porous drawn) with different highly ordered structures were prepared using poly[(R)-3-hydroxybutyrate-co-16 mol%-4-hydroxybutyrate] [P(3HB-co-16 mol%-4HB)], a well-known polyhydroxyalkanoate. Scanning electron microscopy (SEM) images indicated that microorganisms attached to the fiber surface within several days of testing and degraded the fiber without causing physical disintegration. The results of BOD tests revealed that more than 80% of P(3HB-co-16 mol%-4HB) was degraded by microorganisms in the ocean. The plastisphere was composed of a wide variety of microorganisms, and the microorganisms accumulated on the fiber surfaces differed from those in the biofilms. The microbial degradation rate increased as the degree of molecular orientation and porosity of the fiber increased: as-spun fiber < non-porous drawn fiber < porous drawn fiber. The drawing process induced significant changes in the highly ordered structure of the fiber, such as molecular orientation and porosity, without affecting the crystallinity. The results of SEM observations and X-ray measurements indicated that drawing the fibers oriented the amorphous chains, which promoted enzymatic degradation by microorganisms.

Thermal Embedding of Humicola insolens Cutinase: A Strategy for Improving Polyester Biodegradation in Seawater

By thermal embedding of the commercially available enzyme Humicola insolens cutinase (HiC), this study successfully enhanced the biodegradability of various polyesters (PBS, PBSA, PCL, PBAT) in seawater, which otherwise show limited environmental degradability. Melt extrusion above the melting temperature was used for embedding HiC in the polyesters. The overall physical properties of the HiC-embedded films remained almost unchanged compared to those of the neat films. In the buffer, embedding HiC allowed rapid polymer degradation into water-soluble hydrolysis products. Biochemical oxygen demand tests showed that the HiC-embedded polyester films exhibited similar or much higher biodegradability than the biodegradable cellulose standard in natural seawater. Thermal embedding of HiC aims to accelerate the biodegradation of plastics that are already biodegradable but have limited environmental biodegradability, potentially reducing their contribution to environmental problems such as marine microplastics.

Exploring Microorganisms from Plastic-Polluted Sites: Unveiling Plastic Degradation and PHA Production Potential

The exposure of microorganisms to conventional plastics is a relatively recent occurrence, affording limited time for evolutionary adaptation. As part of the EU-funded project BioICEP, this study delves into the plastic degradation potential of microorganisms isolated from sites with prolonged plastic pollution, such as plastic-polluted forests, biopolymer-contaminated soil, oil-contaminated soil, municipal landfill, but also a distinctive soil sample with plastic pieces buried three decades ago. Additionally, samples from Arthropoda species were investigated. In total, 150 strains were isolated and screened for the ability to use plastic-related substrates (Impranil dispersions, polyethylene terephthalate, terephthalic acid, and bis(2-hydroxyethyl) terephthalate). Twenty isolates selected based on their ability to grow on various substrates were identified as Streptomyces, Bacillus, Enterococcus, and Pseudomonas spp. Morphological features were recorded, and the 16S rRNA sequence was employed to construct a phylogenetic tree. Subsequent assessments unveiled that 5 out of the 20 strains displayed the capability to produce polyhydroxyalkanoates, utilizing pre-treated post-consumer PET samples. With Priestia sp. DG69 and Neobacillus sp. DG40 emerging as the most successful producers (4.14% and 3.34% of PHA, respectively), these strains are poised for further utilization in upcycling purposes, laying the foundation for the development of sustainable strategies for plastic waste management.

Marine sponges as bioindicators of pollution by synthetic microfibers in Antarctica

Different marine sponge species from Tethys Bay, Antarctica, were analyzed for contamination by polyester and polyamide microplastics (MPs). The PISA (Polymer Identification and Specific Analysis) procedure was adopted as it provides, through depolymerization and HPLC analysis, highly sensitive mass-based quantitative data. The study focused on three analytes resulting from the hydrolytic depolymerization of polyesters and polyamides: terephthalic acid (TPA), 6-aminohexanoic acid (AHA), and 1-6-hexanediamine (HMDA). TPA is a comonomer found in the polyesters poly(ethylene terephthalate) (PET) and poly(butylene adipate co terephthalate) (PBAT), and in polyamides such as poly(1,4-p-phenylene terephthalamide) (Kevlar™ and Twaron™ fibers) and poly(hexamethylene terephthalamide) (nylon 6 T). AHA is the monomer of nylon 6. HMDA is a comonomer of the aliphatic nylon 6,6 (HMDA-co-adipic acid) and of semi-aromatic polyamides such as, again, nylon 6 T (HMDA-co-TPA). Except for the biodegradable PBAT, these polymers exhibit high to extreme mechanical, thermal and chemical resistance. Indeed, they are used as technofibers in protective clothing able to withstand extreme conditions as those typical of Antarctica. Of the two amine monomers, only HMDA was found above the limit of quantification, and only in specimens of Haliclona (Rhizoniera) scotti, at a concentration equivalent to 27 μg/kg of nylon 6,6 in the fresh sponge. Comparatively higher concentrations, corresponding to 2.5-4.1 mg/kg of either PBAT or PPTA, were calculated from the concentration of TPA detected in all sponge species. Unexpectedly, TPA did not originate from PET (the most common textile fiber) as it was detected in the acid hydrolysate, whereas the PISA procedure results in effective PET depolymerization only under alkaline conditions. The obtained results showed that sponges, by capturing and concentrating MPs from large volumes of filtered marine waters, may be considered as effective indicators of the level and type of pollution by MPs and provide early warnings of increasing levels of pollution even in remote areas.

Identification of a plastic-degrading enzyme from Cryptococcus nemorosus and its use in self-degradable plastics

For decades, plastic waste management has been one of the major ecological challenges of our society. Despite the introduction of biodegradable alternatives such as polylactic acid (PLA), their beneficial environmental impact is limited by the requirement of specific compost facility as biodegradation of PLA in natural environment occurs at a very slow rate. In this work, a plastic-degrading enzyme was utilized to facilitate degradation process. Genomic and proteomic tools were employed to identify a new biodegradable plastic-degrading enzyme from Cryptococcus nemorosus TBRC2959. The new enzyme, Cr14CLE, functions optimally under mild conditions with temperature range of 30 to 40 °C and suffers no significant loss of enzymatic activity at pH ranging from 6 to 8. In addition to PLA, Cr14CLE is capable to degrade other types of biodegradable plastic such as polybutylene succinate (PBS) and polybutylene adipate terephthalate (PBAT) as well as composite bioplastic. Applications of Cr14CLE have been demonstrated through the preparation of enzyme-coated PLA film and laminated PLA film with enzyme layer. PLA films prepared by both approaches exhibited capability to self-degrade in water. KEY POINTS: • Novel plastic-degrading enzyme (Cr14CLE) was identified and characterized. • Cr14CLE can degrade multiple types of biodegradable plastics under mild conditions. • Applications of Cr14CLE on self-degradable plastic were demonstrated.

Controlling primary chain dispersity in network polymers: elucidating the effect of dispersity on degradation

Although dispersity has been demonstrated to be instrumental in determining many polymer properties, current synthetic strategies predominantly focus on tailoring the dispersity of linear polymers. In contrast, controlling the primary chain dispersity in network polymers is much more challenging, in part due to the complex nature of the reactions, which has limited the exploration of properties and applications. Here, a one-step method to prepare networks with precisely tuned primary chain dispersity is presented. By using an acid-switchable chain transfer agent and a degradable crosslinker in PET-RAFT polymerization, the in situ crosslinking of the propagating polymer chains was achieved in a quantitative manner. The incorporation of a degradable crosslinker, not only enables the accurate quantification of the various primary chain dispersities, post-synthesis, but also allows the investigation and comparison of their respective degradation profiles. Notably, the highest dispersity networks resulted in a 40% increase in degradation time when compared to their lower dispersity analogues, demonstrating that primary chain dispersity has a substantial impact on the network degradation rate. Our experimental findings were further supported by simulations, which emphasized the importance of higher molecular weight polymer chains, found within the high dispersity materials, in extending the lifetime of the network. This methodology presents a new and promising avenue to precisely tune primary chain dispersity within networks and demonstrates that polymer dispersity is an important parameter to consider when designing degradable materials.

All-natural environmentally degradable poly (butylene terephthalate-co-caprolactone): A theoretical and experimental study of its degradation properties and mechanisms

The design and production of materials with excellent mechanical properties and biodegradability face significant challenges. Poly (butylene terephthalate-co-caprolactone) copolyesters (PBTCL) is obtained by modifying the engineering plastic polybutylene terephthalate (PBT) with a simple one-pot process using readily biodegradable ε-caprolactone (ε-CL). The material has mechanical properties comparable to those of commercial biodegradable copolyester PBAT. Besides, this copolyester exhibited remarkable degradability in natural environments such as soil and ocean, for example, PBTCL1.91 lost >40 % of its weight after 6 months of immersion in the Bohai Sea. The effect and diversity of specific microorganisms acting on degradation in the ocean were analyzed by 16 s rDNA gene sequencing. Theoretical calculations such as Fukui function and DFT, and experimental studies on water-soluble intermediates and residual matrixes produced after degradation, confirmed that the insertion CL units not only act as active sites themselves susceptible to hydrolysis reactions, but also promote the reactivity of ester bonds between aromatic segments. This work provides insight for the development of novel materials with high performance and environmental degradability.

Polyester Brush Coatings for Circularity: Grafting, Degradation, and Repeated Growth

Polymer brushes are widely used as versatile surface modifications. However, most of them are designed to be long-lasting by using nonbiodegradable materials. This generates additional plastic waste and hinders the reusability of substrates. To address this, we present a synthetic strategy for grafting degradable polymer brushes via organocatalytic surface-initiated ring-opening polymerization (SI-ROP) from stable PGMA-based macroinitiators. This yields polyester brush coatings (up to 50 nm in thickness) that hydrolyze with controlled patterns and can be regrown on the same substrate after degradation. We chose polyesters of different hydrolytic stability and degradation mechanism, i.e., poly(lactic acid) (PLA), polycaprolactone (PCL), and polyhydroxybutyrate (PHB), which are grown from poly(glycidyl methacrylate) (PGMA)-based macroinitiators for strong surface binding and initiating site reuse. Brush degradation is monitored via thickness changes in pH-varied buffer solutions and seawater with PHB brushes showing rapid degradation in all solutions. PLA and PCL brushes show higher stability in solutions of up to pH 8, while all coatings fully degrade after 14 days in seawater. These brushes offer surface modifications with well-defined degradation patterns that can be regrown after degradation, making them an interesting alternative to (meth)acrylate-based, nondegradable polymers brushes.

Synthesis of Stereocontrolled Degradable Polymer by Living Cascade Enyne Metathesis Polymerization

A stereocontrolled degradable polymer was synthesized via living cascade enyne metathesis polymerization. Highly stereodefined N,O-acetal-containing enyne monomers were prepared using the Pd-catalyzed hydroamination of alkoxyallenes and ring-closing metathesis. The resulting chiral polymer exhibited a narrow dispersity window. Block copolymers were prepared not only by sequentially adding nondegradable and degradable monomers but also by using enantiomerically different monomers to produce stereocontrolled blocks. Owing to the hydrolyzable N,O-acetal moiety in the backbone structure, the resulting polymer could degrade under acidic conditions generated using various acid concentrations to control the degradation. Additionally, the aza-Diels-Alder reaction modified the polymer without losing the stereochemistry.

Tetrabutylammonium Halides as Selectively Bifunctional Catalysts Enabling the Syntheses of Recyclable High Molecular Weight Salicylic Acid-Based Copolyesters

To synthesize high molecular weight poly(phenolic ester) via a living ring-opening polymerization (ROP) of cyclic phenolic ester monomers remains a critical challenge due to serious transesterification and back-biting reactions. Both phenolic ester bonds in monomer and polymer chains are highly active, and it is difficult so far to distinguish them. In this work, an unprecedented selectively bifunctional catalytic system of tetra-n-butylammonium chloride (TBACl) was discovered to mediate the syntheses of high molecular weight salicylic acid-based copolyesters via a living ROP of salicylate cyclic esters (for poly(salicylic methyl glycolide) (PSMG), Mn =361.8 kg/mol, Ð<1.30). Compared to previous catalysis systems, the side reactions were suppressed remarkably in this catalysis system because phenolic ester bond in monomer can be selectively cleaved over that in polymer chains during ROP progress. Mechanistic studies reveal that the halide anion and alkyl-quaternaryammonium cation work synergistically, where the alkyl-quaternaryammonium cation moiety interacts with the carbonyl group of substrates via non-classical hydrogen bonding. Moreover, these salicylic acid-based copolyesters can be recycled to dimeric monomer under solution condition, and can be recycled to original monomeric monomers without catalyst under sublimation condition.

Effect of segmental motion on hydrolytic degradation of polyglycolide in electro-spun fiber mats

Recently, environmentally degradable polymers have received great attention from the perspective of sustaining the aquatic environment. To control the degradation behavior of solid polymer materials in an aqueous phase, it is crucial to better understand the thermal molecular motion of polymer chains in water. We herein focus on polyglycolide (PGA), which is one of the representative aliphatic polyesters that are hydrolytically degradable. Three kinds of fiber mats of PGA with different fiber diameters and comparable crystallinities were prepared using an electrospinning method. Our choice of fiber mats was because the ratio of the surface area, where the hydrolytic degradation starts to occur, to the volume was larger than that for the films. Dynamic mechanical analysis (DMA) enabled us to gain direct access to the dynamic glass transition temperature (Tgα) of PGA in the fiber mats both in dry gaseous nitrogen and liquid water. The Tgα value varied not only with the presence of water molecules, but also with the fiber diameter, or the specific surface area. The degradation behavior of PGA fiber mats was examined by immersing the samples in phosphate-buffered saline at various temperatures. When the segmental motion of PGA in the fiber mats was released, the apparent crystallinity of the mats increased, meaning that PGA amorphous chains were cleaved and thus partially eluted into the aqueous phase. It was also shown that partially cleaved chains crystallized.

Highly efficient degradation of polyesters and polyethers by decatungstate photocatalysis

Photocatalytic polymer degradation has been recognized as a promising solution to the global disposal of waste plastics. In this work, we revealed that various polyesters and polyethers were efficiently degraded in the presence of a polyoxometalate photocatalyst, specifically, decatungstate ([W10O32]4-, W10). A catalytic amount of W10 initiated the degradation of various polyesters and polyethers under photo-irradiation with a xenon lamp (λ > 350 nm) using O2 (1 atm) as the oxidant in acetonitrile or water. Moreover, this system can promote polymer degradation even under sunlight. The degradation efficiency, assessed from the degradation rate (Mw0 - Mw)/Mw0 (%) (where Mw0 is the Mw before the reaction), of W10 was notably higher than those of previously reported photocatalysts such as titanium oxide, other polyoxometalates, organometallic compounds, and organic dyes.

Development of Biodegradable Thermosetting Plastic Using Dialdehyde Pineapple Stem Starch

Starch extracted from pineapple stem waste underwent an environmentally friendly modification process characterized by low-energy consumption. This process resulted in the creation of dialdehyde pineapple stem starch featuring varying aldehyde contents ranging from 10% to 90%. Leveraging these dialdehyde starches, thermosetting plastics were meticulously developed by incorporating glycerol as a plasticizer. Concurrently, unmodified pineapple stem starch was employed as a control to produce thermoplastic material under identical conditions. The objective of streamlining the processing steps was pursued by adopting a direct hot compression molding technique. This enabled the transformation of starch powders into plastic sheets without the need for water-based gelatinization. Consequently, the dialdehyde starch-based thermosetting plastics exhibited exceptional mechanical properties, boasting a modulus within the range of 1862 MPa to 2000 MPa and a strength of 15 MPa to 42 MPa. Notably, their stretchability remained relatively modest, spanning from 0.8% to 2.4%. Comparatively, these properties significantly outperformed the thermoplastic counterpart derived from unmodified starch. Tailoring the mechanical performance of the thermosetting plastics was achieved by manipulating the glycerol content, ranging from 30% to 50%. Phase morphologies of the thermoset starch unveiled a uniformly distributed microstructure without any observable starch particles. This stood in contrast to the heterogeneous structure exhibited by the thermoplastic derived from unmodified starch. X-ray diffraction patterns indicated the absence of a crystalline structure within the thermosets, likely attributed to the establishment of a crosslinked structure. The resultant network formation in the thermosets directly correlated with enhanced water resistance. Remarkably, the thermosetting starch originating from pineapple stem starch demonstrated continued biodegradability following a soil burial test, albeit at a notably slower rate when compared to its thermoplastic counterpart. These findings hold the potential to pave the way for the utilization of starch-based products, thereby replacing non-biodegradable petroleum-based materials and contributing to the creation of more enduring and sustainable commodities.

Organocatalyzed ring-opening reactions of γ-carbonyl-substituted ε-caprolactones

Side-chain-functionalized aliphatic polyesters are promising as functional biodegradable polymers. We have investigated ring-opening reactions of γ-carbonyl-substituted ε-caprolactones (gCCLs) to obtain poly(ε-caprolactone) (PCL) analogues. Organic catalysts and Sn(Oct)2 often used for the ring-opening polymerization (ROP) of ε-caprolactone (CL) have been explored to find the conditions for the formation of polymeric products of gCCLs. We confirmed the consumption of gCCLs in all catalyzed reactions. However, chain propagation hardly occurs, as the propagating species are preferentially transformed to α-substituted five-membered lactones when the substituents are linked by ester or not sterically hindered. Intramolecular cyclization to form thermodynamically stable five-membered lactones releases alcohols and amines, serving as nucleophiles for the subsequent ring opening of other gCCLs. Thus, apparent chain reactions are realized for continuous consumption of gCCLs. The reaction preference remains unchanged independent of the catalysts, although the reactions of the amide-linked gCCLs by acidic catalysts are slightly mitigated. Finally, copolymerization of CL and a gCCL catalyzed by diphenyl phosphate has been investigated, which enables the chain propagation reaction to yield the linear oligomers of PCL analogues containing up to 16 mol% of gCCL units. This study contributes to understanding the chemistry of ring-opening reactions of substituted lactones for designing functional degradable polymers.

A Review of Biodegradable Plastics: Chemistry, Applications, Properties, and Future Research Needs

Environmental concerns over waste plastics' effect on the environment are leading to the creation of biodegradable plastics. Biodegradable plastics may serve as a promising approach to manage the issue of environmental accumulation of plastic waste in the ocean and soil. Biodegradable plastics are the type of polymers that can be degraded by microorganisms into small molecules (e.g., H2O, CO2, and CH4). However, there are misconceptions surrounding biodegradable plastics. For example, the term "biodegradable" on product labeling can be misconstrued by the public to imply that the product will degrade under any environmental conditions. Such misleading information leads to consumer encouragement of excessive consumption of certain goods and increased littering of products labeled as "biodegradable". This review not only provides a comprehensive overview of the state-of-the-art biodegradable plastics but also clarifies the definitions and various terms associated with biodegradable plastics, including oxo-degradable plastics, enzyme-mediated plastics, and biodegradation agents. Analytical techniques and standard test methods to evaluate the biodegradability of polymeric materials in alignment with international standards are summarized. The review summarizes the properties and industrial applications of previously developed biodegradable plastics and then discusses how biomass-derived monomers can create new types of biodegradable polymers by utilizing their unique chemical properties from oxygen-containing functional groups. The terminology and methodologies covered in the paper provide a perspective on directions for the design of new biodegradable polymers that possess not only advanced performance for practical applications but also environmental benefits.