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The furan/maleimide Diels–Alder (DA) reaction has been exploited to construct thermally reversible macromolecular structures, such as linear or cross-linked polycondensates, or to cross-link linear polymers, using the free end-type or pending furan and maleimide moieties as the diene and dienophile reagents. Here we report a different approach for the synthesis of homopolymers based on a diol, in which the DA adduct formed by the furan and the maleimide sits within the diol monomer structure. The OH end groups of the diol were used for the synthesis of a polyester and a polyurethane using conventional polycondensation methods and to study their retro DA (rDA) depolymerization through the thermal decomposition of their inner DA adducts. The relevant contribution of this study was however the possibility of synthesizing a copolymer by heating these two polymers together to induce their rDA deconstruction and then lowering the temperature in order to allow the ensuing fragments to recombine statistically by successive DA couplings, thus building the corresponding ester-urethane copolymer. 1H NMR spectroscopy and DSC analysis were employed to confirm the success of this promising approach. [ABSTRACT FROM AUTHOR]

Vat photopolymerization (VPP) of highly aromatic polyurethanes (PUs) expands the library of additive manufacturing (AM) materials and enables a vast array of ductile thermoplastics, rigid and flexible thermosets, and elastomers. Aromatic diisocyanates and various diols enable printing of rigid, highly aromatic cross‐linked parts, which offer high glass transition temperatures and tunable thermomechanical performance. The judicious control of molecular weight of the photo‐reactive telechelic oligomers allows for a fundamental study of the influence of cross‐link density in highly aromatic 3D PU printed objects. VPP AM produces objects with high resolution, smooth surface finish, and isotropic mechanical properties. Thermal post‐processing is critical in maintaining excellent thermomechanical properties with semi‐crystallinity as a function of cross‐link density. Due to the presence of two ester carbonyls in the bis(2‐hydroxyethyl) terephthalate chain extender, the printed parts are readily amenable to depolymerization with methanolysis to produce difunctional dimethyl dicarbamates under modest reaction conditions. Dimethyl dicarbamates serve as suitable monomers for subsequent polycondensation. [ABSTRACT FROM AUTHOR]

Depolymerization and subsequent capture of monomers is of interest for process efficiency and sustainability. Polyamide‐6 (PA‐6) can be depolymerized in aqueous solution using a homogeneous catalyst. To purify the ε‐caprolactam (CPL) monomer and recycle the catalyst, two potential crystallization‐based strategies are studied: direct crystallization from the reaction mixture and liquid‐liquid extraction prior to crystallization. Solubilities in water and promising organic solvents were measured and compared to predictions using perturbed‐chain statistical associating fluid theory (PC‐SAFT) or conductor‐like screening model for real solvents (COSMO‐RS). Detailed solid‐liquid equilibria (SLE) of the CPL/water system were investigated utilizing DSC and PXRD. This work provides an overview of important factors of PA‐6 depolymerization including recycling of tungstophosphoric acid (TPA) and purification of CPL monomers. A first conceptual process design to be further developed is derived. [ABSTRACT FROM AUTHOR]

Delignification of lignocellulose using basic ionic liquids (BILs) such as choline lysinate ([Ch][Lys]) is a promising method due to its high efficiency, mild conditions, and low toxicity. Typically, the following precipitation of lignin by adding acid media makes it challenging to recycle BILs. Herein, we explored a series of low-cost and recyclable alcohols as anti-solvents, including methanol (MeOH), ethanol (EtOH), iso-propanol (i-PrOH), and tert-butanol (t-BuOH), for recovering [Ch][Lys] and precipitating lignin without adding an acid from water-free [Ch][Lys] (case 1) and aqueous [Ch][Lys] (case 2). For case 1, lignin recovery followed the order of EtOH > i-PrOH > t-BuOH (MeOH was not able to recover lignin and [Ch][Lys]), which was negatively correlated with their pKa values, indicating the effect of the inhibited generation of a basic anion (e.g. EtO− from EtOH) from –NH2 in [Ch][Lys] on lignin precipitation. t-BuOH showed the highest lignin recovery of 99.7%, ensuring the high purity of the recovered [Ch][Lys] (recovery of 94.7%). Lignin deprotonation and depolymerization were detected. For case 2, t-BuOH also facilitated the recovery of lignin from an aqueous lignin–[Ch][Lys] system with a nearly quantitative lignin recovery, yet with lower [Ch][Lys] recovery of 81.7% and 64.0% at the [Ch][Lys] : water ratios (w/w) of 7 : 3 and 1 : 9, respectively. The lower recovery of [Ch][Lys] might be due to the poor dispersity of lignin solid in t-BuOH, and water also enhanced the deprotonation of lignin, thus making lignin precipitation more difficult. Based on the results, a deprotonation-based lignin dissolution mechanism has been proposed, which also helps to understand lignin dissolution and precipitation in a [Ch][Lys]-based system. [ABSTRACT FROM AUTHOR]

Efficient pretreatment methods are crucial for the generation of fermentable sugars from the renewable lignocellulose. In this study, γ-valerolactone (GVL), a biomass-derived green solvent, was used to fractionate corn stover (CS). The impact of different additives on the enzymatic hydrolysis and pretreatment of CS within the GVL/water system was carefully investigated. The results demonstrate that the use of H 2 SO 4 -assisted GVL/H 2 O (80:20, w/w) pretreatment at mild conditions successfully facilitates the depolymerization of CS, thereby improving the cellulase accessibility. Furthermore, by increasing the GVL pretreatment temperature to 160 °C with 100 mM H 2 SO 4 addition, the pretreated CS led to nearly 100 % of hydrolysis yield at 2 % (w/v) solid load. Finally, the thermogravimetric analysis (TGA) was performed to evaluate the thermal decomposition characteristics of untreated CS and enzymatic residues based on the H 2 SO 4 -assisted GVL/H 2 O pretreatment. The results indicate that the enzymatic residues had two depolymerization stages from 200 °C to 500 °C with a final residual mass of 22.73 %, which was higher than that of untreated CS (20.56 %). Overall, this study provides an efficient lignocellulose pretreatment for fermentable sugars production and valorization of enzymatic residues. [Display omitted] • Using H 2 SO 4 as γ-valerolactone (GVL) pretreatment additive enhanced xylan removal. • Glucose yield of GVL-pretreated corn stover (CS) was 3–5 folds higher than raw CS. • Sugars production reached 32.4 g/100 g CS by 50 mM H 2 SO 4 -assisted GVL pretreatment. • Enzymatic residues had two decomposition stages in 200–500 °C by thermal analysis. [ABSTRACT FROM AUTHOR]

Low‐strain cyclic olefin monomers, including five‐membered, six‐membered, eight‐membered, and macrocyclic rings, have been recently exploited for the synthesis of depolymerizable polyolefins via ring‐opening metathesis polymerization (ROMP). Such polyolefins can undergo ring‐closing metathesis depolymerization (RCMD) to regenerate their original monomers. Nevertheless, the depolymerization behavior of polyolefins prepared by ROMP of seven‐membered cyclic olefins, an important class of low‐strain rings, still remains unexplored. In this study, we demonstrate the chemical recycling of polyheptenamers to cycloheptene under standard RCMD conditions. Highly efficient depolymerization of polyheptenamer was enabled by Grubbs' second‐generation catalyst in toluene. It was observed that the monomer yields increased when the depolymerization temperature increased and the starting polymer concentration was reduced. A near‐quantitative monomer regeneration (>96%) was achieved within 1 h under dilute conditions (20 mM of olefins) at 60°C. Moreover, polyheptenamer exhibited a decomposition temperature above 430°C, highlighting its potential as a new class of thermally stable and chemically recyclable polymer materials. [ABSTRACT FROM AUTHOR]

Lignins, abundant aromatic biopolymers and one of the major components of lignocellulosic biomass, remain the most underutilized renewable bioresources of aromatics and hydrocarbons on the Earth. Numerous physical and chemical processes have been developed for lignin valorization; however, they generally suffer from environmentally unfriendly, harsh conditions and lack reaction specificity. On the other hand, milder methods involving biocatalysts exist but are impeded by many limitations, such as cofactor regeneration, deleterious enzyme–lignin interactions, and low stability. In this work, we attempt to eliminate the constrains encountered in enzyme‐based lignin valorization processes through the development of a novel electrochemically assisted bioprocess. This “all‐in‐one” biocathode incorporates a hybrid electrocatalytic interface combining a hydrogen peroxide‐generating passive air‐breathing gas diffusion electrode with an immobilized hydrogen peroxide‐consuming lignin peroxidase on a single surface and catalyzing the depolymerization of lignins. The ligninolytic potential of this bioelectrochemical device is demonstrated using both lignin models (veratryl alcohol and veratrylglycerol β‐guaiacyl ether) and a technical lignin at room temperature in aqueous media with the reaction efficiency of 14.9% per hour. [ABSTRACT FROM AUTHOR]

Background: Thymosin beta 4 (Tβ4) is a monomeric actin-binding protein that plays many roles in biological activities. However, some studies on the role of Tβ4 in central axon regeneration have yielded contradictory results. Previous research has focused primarily on cultured cells, leading to a deficiency in in vivo experimental evidence. Therefore, we used a single axon injury model of Mauthner cells in zebrafish larvae to investigate the role of Tβ4 in central axon regeneration in vivo. Results: Our results demonstrated that knockout of Tβ4 impaired axon regeneration, whereas overexpression of Tβ4 promoted axon regeneration. Moreover, this promotion is mediated through the interaction between Tβ4 and G-actin. Furthermore, our results suggest that the binding of Tβ4 to G-actin promotes actin polymerization rather than depolymerization. In the rapid escape behavior test, larvae with damaged axons presented impaired tail muscle control, resulting in a lack of normal tail bending, termed the straight tail phenomenon. The proportion of straight tails was significantly negatively correlated with axon regeneration length, suggesting that it is a new indicator for assessing rapid escape behavior recovery. Finally, the results showed that the overexpression of Tβ4 effectively restored the functionality of rapid escape behaviors mediated by Mauthner cells. Conclusions: Our results provide evidence that Tβ4 promotes central axon regeneration in vivo through binding to G-actin and suggest that Tβ4 could serve as a potential polypeptide drug for clinical therapy. [ABSTRACT FROM AUTHOR]

Polyolefins such as polyethylenes and polypropylenes are the most‐produced plastic waste globally, yet are difficult to convert into useful products due to their unreactivity. Pyrolysis is a practical method for large‐scale treatment of mixed, contaminated plastic, allowing for their conversion into industrially‐relevant petrochemicals. Metal–organic frameworks (MOFs), despite their tremendous utility in heterogeneous catalysis, have been overlooked for polyolefin depolymerization due to their perceived thermal instabilities and inability of polyethylenes and polypropylenes to penetrate their pores. Herein, we demonstrate the viability of UiO‐66 MOFs containing coordinatively‐unsaturated zirconium nodes, as effective catalysts for pyrolysis that significantly enhances the yields of valuable liquid and gas hydrocarbons, whilst halving the amounts of residual solids produced. Reactions occur on the Lewis‐acidic UiO‐66 nodes, without the need for noble metals, and yield aliphatic product distributions distinctly different from the aromatic‐rich hydrocarbons that can be obtained from zeolite catalysis. We also demonstrate the first unambiguous characterization of polyolefin penetration into UiO‐66 pores at pyrolytic temperatures, allowing access to the abundant Zr‐oxo nodes within the MOF interior for efficient C−C cleavage. Our work highlights the potential of MOFs as highly‐designable heterogeneous catalysts for depolymerisation of plastics, which can complement conventional catalysts in reactivity. [ABSTRACT FROM AUTHOR]

We describe a methodology of post‐polymerization functionalization to enable subsequent bulk depolymerization to monomer by utilizing mechanochemical macro‐radical generation. By harnessing ultrasonic chain‐scission in the presence of N‐hydroxyphthalimide methacrylate (PhthMA), we successfully chain‐end functionalize polymers to promote subsequent depolymerization in bulk, achieving up to 82 % depolymerization of poly(methyl methacrylate) (PMMA) and poly(α‐methylstyrene) (PAMS) within 30 min. This method of depolymerization yields a high‐purity monomer that can be repolymerized. Moreover, as compared to the most common methods of depolymerization, this work is most efficient with ultra‐high molecular weight (UHMW) polymers, establishing a method with the potential to address highly persistent, non‐degradable all‐carbon backbone plastic materials. Lastly, we demonstrate the expansion of this depolymerization method to commercial cell cast PMMA, achieving high degrees of depolymerization from post‐consumer waste. This work is the first demonstration of applying PhthMA‐promoted depolymerization strategies in homopolymer PMMA and PAMS prepared by conventional polymerization methods. [ABSTRACT FROM AUTHOR]

Polyethylene (PE) is the most abundantly sourced plastic and significant efforts are needed for its end-of-life management. The deconstruction of PE is an uphill task and requires the breaking of highly stable C–C bonds. Here we demonstrate that PE can be deconstructed to value-added dodecene, along with other long-chain alkenes. The PCP–iridium complex catalyzes the dehydrogenation of commercial and post-consumer polyethylene waste to produce dehydrogenated polyethylene (DHP) with 0.5–1.0% unsaturation. The DHP was subjected to an ethylene cross-metathesis reaction in the presence of suitable catalysts. Through meticulous optimization of reaction parameters, 63% selectivity toward dodecene, with 26% overall yield, was achieved. The practical significance of our method has been demonstrated by subjecting post-consumer plastic waste to dehydrogenation followed by ethylene metathesis to produce dodecene as a major product, together with long-chain alkenes. The PE deconstruction has been confirmed by recording molar mass before and after depolymerization using high-temperature gel permeation chromatography. The existence of dodecene has been unambiguously ascertained using GC, GC-MS, NMR, and IR spectroscopy. Thus, these results demonstrate the conversion of waste PE to value-added dodecene and long-chain alkenes under mild reaction conditions. [ABSTRACT FROM AUTHOR]

The modification of molybdenum carbide catalysts by another transition metal has raised an increasing research interest due to the significant improvement of catalyst activity in hydrodeoxygenation of lignin derivatives. At par with the commonly used Co and Ni that add a strong hydrogenation functionality, it was found that the addition of the more oxophilic W restricts ring hydrogenation while allowing the deoxygenation of oxygenated compounds and thus yielding higher selectivity toward the formation of non‐oxygenated aromatic compounds. The coexistence of Mo2C with W2C along with metallic W altered the electronic properties of Mo2C which resulted in an increase of catalyst active site density and facilitated further total eugenol deoxygenation. Propyl‐benzene selectivity of up to 83 % was reached at close to 100 % eugenol conversion. These findings will allow a better overview of the effect of different metal phases of mixed carbides on the catalyst performance and raise the prospect of optimizing catalyst design for a hydrodeoxygenation processing of lignin depolymerization products. [ABSTRACT FROM AUTHOR]

Microtubule organising centres (MTOCs) are sites of localised microtubule nucleation in eukaryotic cells. Regulation of microtubule dynamics often involves KATANIN (KTN): a microtubule severing enzyme that cuts microtubules to generate new negative ends, leading to catastrophic depolymerisation. In Arabidopsis thaliana, KTN is required for the organisation of microtubules in the cell cortex, preprophase band, mitotic spindle and phragmoplast. However, as angiosperms lack MTOCs, the role of KTN in MTOC formation has yet to be studied in plants. Two unique MTOCs - the polar organisers - form on opposing sides of the preprophase nucleus in liverworts. Here, we show that KTN-mediated microtubule depolymerisation regulates the number and organisation of polar organisers formed in Marchantia polymorpha. Mpktn mutants that lacked KTN function had supernumerary disorganised polar organisers compared with wild type. This was in addition to defects in the microtubule organisation in the cell cortex, preprophase band, mitotic spindle and phragmoplast. These data are consistent with the hypothesis that KTN-mediated microtubule dynamics are required for the de novo formation of MTOCs, a previously unreported function in plants. [ABSTRACT FROM AUTHOR]

This paper presents a detailed physical model for a novel method of two- and three-dimensional microstructure formation: dry electron beam etching of the resist (DEBER). This method is based on the electron-beam induced thermal depolymerization of positive resist, and its advantages include high throughput and relative simplicity compared to other microstructuring techniques. However, the exact mechanism of profile formation in DEBER has been unclear until now, hindering the optimization of this technique for certain applications. The developed model takes into account the major DEBER phenomena: e-beam scattering in resist and substrate, e-beam induced main-chain scissions of resist molecules, thermal depolymerization of resist, monomer diffusion, and resist reflow. Based on the developed model, a simulation algorithm was implemented, which allowed simulation of the profile obtained in resist by DEBER. Experimental verification of the DEBER model was carried out, which demonstrated the reliability of the model and its applicability for theoretical study of this method. The ultimate DEBER characteristics were estimated by simulation. The minimum line width and the maximum profile slope that could be obtained by DEBER were approximately 300 nm and 70°, respectively. [ABSTRACT FROM AUTHOR]

The self‐plasticization, i.e., the increase in the polymer chains' mobility by including its monomer, has a major impact on a polymer's structural, thermal, and mechanical properties. In this study, differential scanning calorimetry (DSC), optical and Raman microscopies, thermo‐mechanical analysis (TMA), size exclusion chromatography equipped with a multi‐angle light scattering detector (SEC‐MALS), and X‐ray diffraction analysis (XRD) are used to investigate the effect of thermally induced self‐plasticization of poly‐(p‐dioxanone), PDX, on the crystal growths from the amorphous and molten states. Significant changes in the crystallization behavior and mechanical properties of PDX are found only for samples self‐plasticized at the depolymerization temperature (Td) above 150 °C. The intense self‐plasticization leads to the decrease of the crystallization temperature, increase of the crystal growth rapidity, disappearance of the distinct α→α' polymorphic transition, reduction of the overall melting temperature, and segregation of the redundant monomer. Although the morphology of the crystalline phase has a major impact on the mechanical properties of PDX, the self‐plasticization itself does not seem to result in any major changes in the magnitude, localization, or morphology of formed crystallites (these are primarily driven by the temperature of crystal growth). The manifestation of the variable activation energy concept is discussed for the present crystallization data. [ABSTRACT FROM AUTHOR]

Transition metal catalysis plays a pivotal role in chemical synthesis. Noble metals often grab significant attention in organometallic catalysis due to their high reactivity. However, the serious issues associated with these metals such as low abundance, toxicity, geopolitical limitations, and volatile prices are driving the scientific community to discover sustainable alternatives. In this context, iron appears to be the first choice as an alternative metal due to its unique properties, including a range of stable oxidation states, Lewis acidity, high abundance in the earth's crust, and low toxicity. Over the past two decades, substantial progress has been made in iron catalysis. This overview examines the recent developments in iron‐catalyzed industrially relevant transformations such as hydroformylation, olefin isomerization, hydrosilylation, hydrophosphination, carbonylation, Wacker‐type oxidation, and plastic depolymerization. As witnessed throughout this review, the performance of iron can be significantly altered by suitable ligand selection and by tailoring the electronic and steric properties of the iron center. While noble metals remain the industry work‐horse, iron is inching closer and with extensive scientific understanding, it may replace noble metals in the near future. [ABSTRACT FROM AUTHOR]

ABSTRACT Hyaluronic acid (HA) is extensively utilized in biomedical applications, and its functionality can be enhanced by introducing aldehyde groups (─CHO) through oxidation. In this study, cold atmospheric plasma (CAP) was used to treat aqueous HA solutions, resulting in the formation of plasma‐modified HA (PMHA) containing ─CHO groups. The free radicals generated from interactions between water molecules and CAP particles reacted with HA, leading to the oxidation of hydroxyl groups into ─CHO and the cleavage of glycosidic bonds, causing molecular depolymerization. The PMHA was then used to synthesize hydrogels in combination with carboxymethyl chitosan and ɛ‐polylysine. This study presents an effective approach for generating HA with aldehyde functionalities and offers insights into the interaction between CAP and polysaccharides. [ABSTRACT FROM AUTHOR]

The extensive utilization of plastic, as a symbol of modern technological society, has consumed enormous amounts of finite and non-renewable fossil resources and produced huge amounts of plastic wastes in the land or ocean, and thus recycling and reuse of the plastic wastes have great ecological and economic benefits. Closed-loop recyclable polymers with inherent recyclability can be readily depolymerized into monomers with high selectivity and purity and repolymerized into polymers with the same performance. They are deemed to be the next generation of recyclable polymers and have captured great and increasing attention from academia and industry. Herein, we provide an overview of readily closed-loop recyclable polymers based on monomer and polymer design and no-other-reactant-involved reversible ring-opening and addition polymerization reactions. The state-of-the-art of circular polymers is separately summarized and discussed based on different monomers, including lactones, thiolactones, cyclic carbonates, hindered olefins, cycloolefins, thermally labile olefin comonomers, cyclic disulfides, cyclic (dithio) acetals, lactams, Diels–Alder addition monomers, Michael addition monomers, anhydride–secondary amide monomers, and cyclic anhydride–aldehyde monomers, and polymers with activatable end groups. The polymerization and depolymerization mechanisms are clearly disclosed, and the evolution of the monomer structure, the polymerization and depolymerization conditions, the corresponding polymerization yield, molecular weight, performance of the polymers, monomer recovery, and depolymerization equipment are also systematically summarized and discussed. Furthermore, the challenges and future prospects are also highlighted. [ABSTRACT FROM AUTHOR]

A synergistic photocatalytic system based on Fe-based perovskite with persulfate was constructed for alkali lignin (AL) degradation in pulp and paper wastewater. The degradation performance and mechanism on AL were carried out under ambient temperature and pressure, accompanied by visible light irradiation. The results showed that the synergistic photocatalytic system exhibited much better performance on AL degradation than the single catalytic system. The degradation efficiency reached 73.5% under the optimal conditions and was constant at around 65% over the pH range from 2 to 8. A significant escalation of the AL degradation was observed at pH 10, reaching 80.1%. The photogenerated holes, 1O2 and SO4−·, generated by the system were involved in the degradation, and the holes played a dominant role. During the degradation process, the efficient promotion of cleavage events in lignin methoxy, β-O-4 bond, and benzene ring was observed. Consequently, the depolymerization process led to the generation of high-value compounds, namely p-hydroxybenzaldehyde and vanillin. Remarkably, the yields of the high-value compounds in the synergistic photocatalytic system were five times larger than those in the control. This study offered a viable method to activate persulfate for alkali lignin degradation and to achieve a mutually beneficial strategy for wastewater treatment and recycling. [ABSTRACT FROM AUTHOR]

Polyester especially polyethylene terephthalate PET is widely used in the textile and apparel industries due to its excellent thermal mechanical and chemical stability. However with increasing consumption the environmental impact of waste polyester fibers has become increasingly pronounced. The problem in biodegrading PET poses technical challenges for the recycling and reuse of waste polyester particularly in terms of efficient depolymerization and the recovery of valuable chemical monomers. Traditional methods for dealing with waste polyester are plagued by low efficiency high costs cumbersome processes and significant environmental pollution. Therefore developing efficient economical and energy-conserving recycling technology for waste polyester is significant for alleviating environmental pressure and achieving resource recycling. This study aims to explore a novel water-solvent thermal technology for the efficient depolymerization of waste polyester and the recovery of terephthalic acid TPA providing a new approach for the highvalue recycling of waste polyester. To efficiently depolymerize waste polyester and recover TPA this study employed water-solvent thermal technology. Waste polyester pellets were treated with an alkaline water-methanol solution under high temperature and pressure followed by the precipitation of TPA using sulfuric acid. The process conditions for the depolymerization of polyester in the alkaline water-methanol solution were optimized. Various analytical techniques including Fourier transform infrared spectroscopy FTIR nuclear magnetic resonance NMR spectroscopy and high-performance liquid chromatography HPLC were used to characterize the chemical properties and purity of the obtained TPA. Additionally the VeriVide DigiEye Roachelab system was used to evaluate the color characteristics of the product. The use of hydro-solvent thermal technology in this study achieved efficient depolymerization of waste polyester and the use of sulfuric acid facilitated the efficient precipitation of TPA. The systematic optimization of depolymerization process parameters provided a basis for further improving the recovery rate and reducing costs. The experimental results showed that when waste polyester granules were treated in a mixture containing 50 g / L of sodium hydroxide and 100 mL/ L methanol at 160 ℃ for 2. 5 hours with a bath ratio of 1︰20 the recovery rate of TPA was calculated to be 94. 9% . The chemical properties of the separated product as indicated by FTIR NMR and HPLC analysis were highly consistent with the TPA standard showing a purity of 90. 53% . However the color difference between commercial TPA and the obtained TPA was 16. 02 according to the VeriVide DigiEye Roachelab system indicating the presence of a small amount of light yellow impurities. This study has significant value in practical application and environmental protection. The optimization of depolymerization conditions provides key reference information for the industrial-scale recycling of waste polyester which can help improve production efficiency and effectively reduce economic costs. Moreover this study proposes a new method for the efficient recovery of TPA from waste polyester which not only reduces the potential environmental impact of waste polyester fibers but also promotes the further development of the circular economy. However there are some limitations in the research process that point the way for future work. For example the TPA product obtained in the experiment shows a significant color difference compared to the standard one indicating that the product contains a certain amount of impurities. This necessitates the exploration of more effective purification technologies in future research to improve the purity and quality of the product. Additionally during the experimental process ethylene glycol EG was observed in the hydrolysate but due to its low content it is difficult to achieve effective separation. This issue also needs to be resolved in future research to fully recover and utilize all valuable components in waste polyester. In summary although this study has made positive progress in the depolymerization of waste polyester and the recovery of TPA further research and improvement are still needed to overcome current challenges and achieve a more efficient and environmentally friendly recycling process. [ABSTRACT FROM AUTHOR]

Replacing fossil resources as the primary source of carbon‐based chemicals by alternative feedstocks, while implementing more sustainable production routes, has become imperative for environmental and resource sustainability. In this context, lignin, often treated as a biomass waste, emerges as an appealing candidate, considering the principles of circular economy. For this pursuit, depolymerization methods offer potential strategies to harness lignin to produce valuable organic chemicals, while electrocatalysis processes stand out especially in the context of sustainability, as they can be powered by electricity from renewable sources. This minireview article explores the pivotal role of various electrocatalysts in lignin depolymerization, investigating both oxidative and reductive pathways. Emphasizing recent advancements, the review delves into the diverse nature of electrocatalysts and their influence on lignin valorization. Highlighting current trends, the discussion encompasses the catalytic mechanisms and selectivity of electrochemical processes employed for lignin breakdown. Additionally, some insights into emerging technologies are also offered, emphasizing the need for sustainable and efficient strategies. By providing an overview of the field, this minireview aims to guide future research endeavors toward innovative electrocatalytic approaches for lignin depolymerization, paving the way for sustainable biorefinery processes. [ABSTRACT FROM AUTHOR]

The main objective of this study was to carry out modification of Amaranthus starch (via oxidation and heat moisture treatment (HMT)) followed by the formation of edible films. The films were evaluated for physicochemical and mechanical properties. The carboxyl content of native and HMT starch was found to be similar whereas it was higher (0.1 COOH/100GU) for the oxidized sample. The solubility was found to be higher in modified starch samples (76.44 %) as compared to native (62.58 %) but swelling power was higher for native starch (50.43 g/g) as compared to modified samples. The tasting temperature of native starch, oxidized, and heat moisture-treated starch was found to be 75.09 °C, 76.10 °C, and 89.36 °C, respectively. Edible films were prepared and studied for physicochemical and mechanical. The tensile strength of amaranth starch films was enhanced by both modification procedures, whereas only HMT increased the water vapor permeability, and oxidation had the opposite effect. Modification treatments resulted in the reduction of water solubility of the films. The HMT film showed some advantages over the oxidized film and native starch films in terms of mechanical properties. The present study conclude that modified starches showed better properties than native starch. [ABSTRACT FROM AUTHOR]

Different forms of HCOOH in the depolymerization system play an important role in governing the monomeric products from lignin. We reported two strategies for the introduction of HCOOH to enrich the monophenols from kraft lignin by microwave‐assisted depolymerization. The reaction of lignin models showed that HCOOH was in favor of the cleavage of C−O bonds (β‐O‐4 typically) and partial C−C bonds (Cα−Cβ). Subsequently, Microwave‐assisted depolymerization of lignin with two strategies was conducted via a designed dynamic vapor flow reaction system. Strategy A with HCOOH as pretreatment solvent showed excellent monophenols enrichment with total mass yields of 193.71 mg/g (lignin basis). Strategy B using HCOOH as reforming solvent vapor significantly increased the monophenols selectivity. It presented unique reforming and upgrading performance by generating catechol (42.59 mg/g, lignin basis) and homovanillic acid (17.58 mg/g, lignin basis). This study provided potential strategies for the efficient conversion of kraft lignin into high‐value platform chemicals. [ABSTRACT FROM AUTHOR]

Developing plastics that fill the need of polyolefins yet are more easily recyclable is a critical need to address the plastic waste crisis. However, most efforts in this vein have focused on high‐density polyethylene (PE), while many different types of PE exist. To create broadly sustainable PE with modular properties, we present the synthesis, characterization, and demonstration of materials applications for chemically recyclable PE‐like multiblock polymers prepared from distinct hard and soft blocks using ruthenium‐catalyzed dehydrogenative polymerization. By altering the branching pattern within the soft blocks, a series of PE‐like multiblock polymers were synthesized with tunable glass transition temperatures (Tg) while maintaining consistent high melting temperatures (Tm). A clear U‐shape trend between Tg and mechanical properties was found, showcasing their potential as sustainable materials with tailored properties spanning commercial linear low‐density polyethylene (LLDPE) and low‐density polyethylene (LDPE). These materials offer adjustable adhesive strength to metal and demonstrate chemical recyclability and selective depolymerization in mixed plastic streams, promoting circularity and separation. [ABSTRACT FROM AUTHOR]

Global production of synthetic polyamides (PA), or nylons, is increasing while recycling rates are currently below 5% contributing to the global plastics crisis. Enzymatic depolymerization is a powerful strategy to overcome the drawbacks of mechanical and chemical recycling and has the potential to increase PA recycling rates. However, enzymatic depolymerization of PA is currently limited to a small group of nylonases (NylC) that exhibit low activities making them unsuitable for efficient enzymatic recycling. In this study, we extend the diversity of nylonases, namely NylC1, NylC2, and NylC3 by library screenings and in silico analysis. Three novel nylonases were identified that showed varying sequence identities ranging from 84 to 32% compared to the previously characterized NylCp2 from Paenarthrobacter ureafaciens. Activity of these nylonase candidates towards cyclic PA-oligomers was confirmed via the detection of soluble degradation products. These nylonases were also active on synthesized poly(ester amides) (PEA), and this activity was synergistically increased by combination with the leaf and branch compost cutinase LCC resulting in the hydrolysis of approximately 1% of the total polymer. Overall, our discoveries greatly increase the sequence space of NylC enzymes for future enzyme engineering strategies to boost their activities, and they show the potential of PEA for tuning the biodegradability of performance polymers. Thereby, this study leads the path for developing efficient enzymatic PA and PEA depolymerization processes, revealing significant insights into combining the contrary parameters of performance and biodegradability of polymers. [ABSTRACT FROM AUTHOR]

Mononuclear and multinuclear O^N^O‐donor Zn(II) complexes are herein reported as catalysts in the ring‐opening polymerization (ROP) of rac‐lactide (rac‐LA) and depolymerization of poly(lactide) (PLA). Reactions of imino‐phenol proligand 2[((2‐hydroxyethyl)imino)methyl]phenol (L1H2) with ZnCl2 and ZnEt2 afforded the dinuclear and tetranuclear complexes [Zn2(L1H)2Cl2] (Zn1) and [Zn4(L1)4] (Zn2), respectively. Separately, treatments of proligands 2‐[1‐((2‐hydroxyethyl)imino)ethyl]phenol (L2H2) and [((2‐methoxyethyl)imino)methyl]phenol (L3H) with ZnCl2 gave the respective mononuclear complexes [Zn(L2H2)2Cl2] (Zn3) and [Zn(L3H)2Cl2] (Zn4), while the reactions of L3H with ZnEt2 afforded the bis(chelated) mononuclear complex [Zn(L3)2] (Zn5). The complexes were characterized using NMR and IR spectroscopy, elemental analyses and single crystal X‐ray crystallography. All the Zn(II) complexes showed high catalytic activities in the ROP of rac‐LA (kapp of up to 4.18 × 10−4 s−1) to give moderate molecular weight PLA (39,960 g mol−1) with relatively narrow dispersities (Đ = 1.4–2.1). The complexes produced mainly atactic PLAs with Pr values of 0.51–0.58. More significantly, complexes Zn1, Zn2, and Zn5 were also active in the depolymerization of commercial PLA in methanol (kapp of up to 2.67 × 10−4 s−1) to produce alkyl lactates. The ROP and depolymerization behavior were largely controlled by the structure and nuclearity of the complexes. [ABSTRACT FROM AUTHOR]

A ternary iron–cobalt–nickel hydroxide nanoarray catalyst was fabricated, which achieves enhanced performance towards electro-oxidative depolymerization of lignin models to produce benzoic acid and phenol. [ABSTRACT FROM AUTHOR]

The development of modern society is closely related to polymer materials. As a typical example, plastic is an indispensable material in modern society. However, despite their low cost and widespread use, most discarded polymers are not recyclable, and their widespread use leads to the depletion of natural resources. In addition, the accumulation of polymer materials and their evolution in the environment can also cause serious environmental problems. Although the polymers can be reused by physical recovery, the properties of the polymers produced by this process are significantly reduced. Chemical recycling to original monomers for repolymerization offers a promising closed‐loop method to transition from a linear plastic economy toward a more sustainable circular model. This review focuses on recent developments and outlines future challenges of emerging chemically recyclable polyesters. [ABSTRACT FROM AUTHOR]

Actin filament turnover involves subunits binding to and dissociating from the filament ends, with the pointed end being the primary site of filament disassembly. Several molecules modulate filament turnover, but the underlying mechanisms remain incompletely understood. Here, we present three cryo-EM structures of the F-actin pointed end in the presence and absence of phalloidin or DNase I. The two terminal subunits at the undecorated pointed end adopt a twisted conformation. Phalloidin can still bind and bridge these subunits, inducing a conformational shift to a flattened, F-actin-like state. This explains how phalloidin prevents depolymerization at the pointed end. Interestingly, two DNase I molecules simultaneously bind to the phalloidin-stabilized pointed end. In the absence of phalloidin, DNase I binding would disrupt the terminal actin subunit packing, resulting in filament disassembly. Our findings uncover molecular principles of pointed end regulation and provide structural insights into the kinetic asymmetry between the actin filament ends. The pointed end of actin filaments is a dominant site of actin depolymerization. Here, the authors show how the actin modulators phalloidin and DNase I interact with the pointed end to either stabilize its arrangement or to promote its disassembly. [ABSTRACT FROM AUTHOR]

While a large number of chemically recyclable thermoplastics have been developed in recent years, technologically important thermoplastic elastomers (TPEs) that are not only bio-based and fully recyclable but also exhibit mechanical properties that can rival or even exceed those petroleum-based, non-recyclable polyolefin TPEs are critically lacking. The key challenge in developing chemically circular, bio-based, high-performance TPEs rests on the complexity of TPE's block copolymer (BCP) structure involving block segments of different suitable monomers required to induce self-assembled morphologies responsible for performance as well as the control and monomer compatibility in their synthesis and the selectivity in their depolymerization. Here we demonstrate the utilization of bio-sourced δ-valerolactone (δVL) and its simple α-alkyl-substituted derivatives to produce all δVL-based polyester tri-BCP TPEs, which exhibit not only complete (closed-loop) chemical recyclability but also excellent toughness that is 2.5–3.8 times higher than commercial polyolefin-based TPEs. The visualized cylindrical morphology formed via crystallization-driven self-assembly in the new all δVL tri-BCP is postulated to contribute to the excellent TPE property. While a large number of chemically recyclable thermoplastics have been developed in recent years, technologically bio-based and fully recyclable thermoplastic elastomers (TPEs) with excellent mechanical properties are lacking. Here the authors demonstrate an all δvalerolactone-based polyester tri-BCP TPEs, which exhibit not only closed-loop chemical recyclability but also exceptional toughness. [ABSTRACT FROM AUTHOR]

The valorization of native lignin to functionalized aromatic compounds under visible light is appealing yet challenging. In this communication, colloidal mercaptoalkanoic acid capped ultrathin ZnIn2S4 (ZIS) microbelts was successfully fabricated, which was used as a superior catalyst for depolymerization of native lignin in birch woodmeal under visible light, with an optimum yield of 28.8 wt % to functionalized aromatic monomers achieved in 8 h. The capped mercaptoalkanoic acid not only enables a solvent modulated reversible interchange of ZIS between the colloidal state for efficient reaction and the aggregated state for facile separation, but also serves as a precursor for light initiated generation of reactive thiyl radical for highly selective cleavage of β‐O‐4 bond in native lignin. This work provides a green and efficient strategy for the depolymerization of native lignin to functionalized aromatic monomers under mild conditions, which involves a new mechanism for the cleavage of β‐O‐4 bonds in native lignin. The capability of cleavage of β‐O‐4 bonds in native lignin by photogenerated thiyl radicals also demonstrates the great potential of using photogenerated thiyl radicals in organics transformations. [ABSTRACT FROM AUTHOR]

We present an innovative process for directly transforming poly(ethylene terephthalate) (PET), a polymer extensively used in food and beverage packaging, into trans‐isomer‐enriched 1,4‐cyclohexanedimethanol (CHDM), a key ingredient in advanced specialty polymers. Our approach leverages a dual‐catalyst system featuring palladium on reduced graphene oxide (Pd/r‐GO) and oxalate‐gel‐derived copper‐zinc oxide (og‐CuZn), utilizing hydrogenation/hydrogenolysis relay catalysis. This method efficiently transforms PET into polyethylene‐1,4‐cyclohexanedicarboxylate (PECHD), which is then converted into CHDM with an impressive overall yield of 95 % in a two‐stage process. Our process effectively handles various post‐consumer PET plastics, converting them into CHDM with yields between 78 % and 89 % across different substrates. Additionally, we demonstrate the applicability and scalability of this approach through a temperature‐programmed three‐stage relay process on a 10‐gram scale, which results in purified CHDM with an isolated yield of 87 % and a notably higher trans/cis ratio of up to 4.09/1, far exceeding that of commercially available CHDM. This research not only provides a viable route for repurposing PET waste but also enhances the control of selectivity patterns in multistage relay catalysis. [ABSTRACT FROM AUTHOR]

The cleavage of C−O bonds is one of the most promising strategies for lignin‐to‐chemicals conversion, which has attracted considerable attention in recent years. However, current catalytic system capable of selectively breaking C−O bonds in lignin often requires a precious metal catalyst and/or harsh conditions such as high‐pressure H2 and elevated temperatures. Herein, we report a novel protocol of paired electrolysis to effectively cleave the Cβ−O−4 bond of lignin model compounds and real lignin at room temperature and ambient pressure. For the first time, "cathodic hydrogenolysis of Cβ−O−4 linkage" and "anodic C−H/N−H cross‐coupling reaction" are paired in an undivided cell, thus the cleavage of C−O bonds and the synthesis of valuable triarylamine derivatives could be simultaneously achieved in an energy‐effective manner. This protocol features mild reaction conditions, high atom economy, remarkable yield with excellent chemoselectivity, and feasibility for large‐scale synthesis. Mechanistic studies indicate that indirect H* (chemical absorbed hydrogen) reduction instead of direct electron transfer might be the pathway for the cathodic hydrogenolysis of Cβ−O−4 linkage. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate (PET), a widely used polymer in the production of single-use plastics, is a significant contributor to the global plastic pollution problem. This work explores the synergistic effects between clay matrices and active Nb 2 O 5 catalytic species, emphasizing the enhanced catalytic performance for the aminolytic depolymerization of PET and polyester (PES) wastes. The materials were well characterized using XRD, SEM-EDS, FTIR, and UV-DRS studies. The surface parameters of Nb 2 O 5 were enhanced by forming a composite with kaolin, which is confirmed by BET isotherms. Kaolin provides a large surface area, which enhances the dispersion and interaction of the niobia catalyst. The combination of kaolin and niobia acts as an effective catalyst for the depolymerization of PET, breaking down the polymer into its monomeric constituents. The catalytic efficiency of Nb 2 O 5 (82 %) has been enhanced in the presence of kaolin support (95 %), forming depolymerized bis(2-hydroxyethyl)terephthalamide (BHETA) and excellent reusability and stability of up to five subsequent cycles thereby emphasizing their potential for sustained performance in industrial applications and contributing to the ongoing discourse on advancing catalyst technologies for enhanced environmental impact in the circular economy. [ABSTRACT FROM AUTHOR]

For the upcycling of waste polyethylene terephthalate (PET), encompassing both colored and fabric PET materials, we investigated the Ir(triNHC)‐catalyzed dehydrogenative coupling of PET and methanol, leading to the production of sodium lactate with good yields. We proposed a sustainable method for isolating lactic acid from the catalytic reaction mixture of sodium lactate and regenerating the base using bipolar membrane electrodialysis (BMED). This isolation method demonstrated high effectiveness, achieving isolation of lactic acid while maintaining economic feasibility at $ 0.10 per kg of lactic acid, and enabling sustainable NaOH regeneration with complete resource circulation. We assessed the recyclability of the catalyst and elucidated the mechanism involving base‐mediated depolymerization and catalyst‐promoted dehydrogenation, highlighting the importance of triNHC ligands in enhancing catalytic activity. [ABSTRACT FROM AUTHOR]

Carboxymethylglucans (CMGs) are widely used semisynthetic polyelectrolytes, e.g., for pharmaceuticals. They are produced in heterogeneous processes on activated starch granules or cellulose fibers. In contrast to neutral ether derivatives, a lower DS in the range, commonly between 0.6 and 1.2, is sufficient to achieve the water solubility of CM cellulose. The high proportion of unsubstituted domains, which could aggregate and therefore only swell and form gel particles but do not dissolve, places higher demands on the statistical distribution of the substituents. The knowledge of regioselectivity, essential for the interpretation of higher structural-level data, can be obtained by various methods, preferentially by CE/UV after hydrolysis. To study the distribution of substituents at the polymer level by mass spectrometric (MS) analysis, partial random depolymerization is required. Due to the ionic character and acid functionality, all the attempts of the direct depolymerization of CMG and further sample preparation suffered from bias, side reactions, and multiple ion formation in MS. Finally, the transformation of CMGs to the corresponding hydroxyethylglucans (HEGs) by the reduction of the esterified carboxy groups with LiAlH4 opened the window for quantitative oligomer MS analysis. While the CM amyloses were reduced quantitatively, the transformation of the CMC was only about 60% but without the formation of mixed CM/HE ethers. [ABSTRACT FROM AUTHOR]

Cellulose is one of the most abundant renewable resources in nature. However, its recalcitrant crystalline structure hinders efficient enzymatic depolymerization. Unlike cellulases, lytic polysaccharide monooxygenases (LPMOs) can oxidatively cleave glycosidic bonds in the crystalline regions of cellulose, playing a crucial role in its enzymatic depolymerization. An AA9 LPMO from Myceliophthora thermophila was previously identified and shown to exhibit a highly efficient catalytic performance. To further enhance its catalytic efficiency, consensus mutagenesis was applied. Compared with the wild-type enzyme, the oxidative activities of mutants A165S and P167N increased by 1.8-fold and 1.4-fold, respectively, and their catalytic efficiencies (kcat/Km) improved by 1.6-fold and 1.2-fold, respectively. The mutants also showed significantly enhanced activity in the synergistic degradation of cellulose with cellobiohydrolase. Additionally, the P167N mutant exhibited better H2O2 tolerance. A molecular dynamics analysis revealed that the increased activity of mutants A165S and P167N was due to the closer proximity of the active center to the substrate post-mutation. This study demonstrates that selecting appropriate mutation sites via a semi-rational design can significantly improve LPMO activity, providing valuable insights for the protein engineering of similar enzymes. [ABSTRACT FROM AUTHOR]

As the only natural source of aromatic biopolymers, lignin can be converted into value-added chemicals and biofuels, showing great potential in realizing the development of green chemistry. At present, lignin is predominantly used for combustion to generate energy, and the real value of lignin is difficult to maximize. Accordingly, the depolymerization of lignin is of great significance for its high-value utilization. This review discusses the latest progress in the field of lignin depolymerization, including catalytic conversion systems using various thermochemical, chemocatalytic, photocatalytic, electrocatalytic, and biological depolymerization methods, as well as the involved reaction mechanisms and obtained products of various protocols, focusing on green and efficient lignin depolymerization strategies. In addition, the challenges faced by lignin depolymerization are also expounded, putting forward possible directions of developing lignin depolymerization strategies in the future. [ABSTRACT FROM AUTHOR]

The degradation and recycling of waste epoxy resins is an urgent environmental problem, encouraging the use of degradable thermosetting epoxies. In this study, a high-performance thermosetting epoxy resin material that can be easily degraded and recycled was prepared using a low-viscosity and high-activity epoxy monomer, tetrahydrophthalic acid diglycidyl ester. Owing to the breakable ester bond in this epoxy monomer, the thermosetting three-dimensional epoxy cross-linked structure can be rapidly degraded using ethylene glycol at atmospheric pressure. After further depolymerization of the epoxy resin/glycol solution with NaOH, sodium cyclohexene-2-carboxylate was obtained. The sodium salt was acidified, epoxidized, and then re-prepared to obtain the epoxy monomer diglycidyl tetrahydrophthalate. The recycled epoxy monomer possesses the same thermal and mechanical properties as the original epoxy monomer, thus realizing the economic and environmentally friendly degradation and recycling of the thermosetting epoxy resin under mild conditions, and this recycling method is applicable to epoxy systems with ester bonding in the cured material. [ABSTRACT FROM AUTHOR]

Landfilled solid waste polymers were converted into high octane green fuels and hydrocarbons by a catalytic depolymerization process. Experiments were conducted in a batch catalytic reactor pressurized with methane as a co-feed. Design of Experiments (DOE) methodology was used for process optimization and parametric study. The operating conditions that maximize the liquids aromatic hydrocarbons were found using response optimizer tool. The reaction temperature and polymer to catalyst ratio (PCR) were found to have significant effects on the responses and methane pressure was not significant for yields of solids, liquids and gaseous products. However, pressurized methane facilitated dehydrocyclization reactions resulting in increased monoaromatic hydrocarbons in the final liquid products. Experiments conducted with methane feed at optimized reaction conditions resulted in 89% aromatic hydrocarbons, 8% paraffins and about 3% other hydrocarbons in liquid products. Aromatic products included benzene (6.5%), toluene (25%), xylenes (27%), ethylbenzene (4.5%), other monoaromatics (22%) and polyaromatic hydrocarbons (4%). Gaseous products contained propylene (47%) and hydrogen (23.9%). The utilization of waste polymers as feedstock materials, flare gas (methane) as a co-feed, and zeolite catalysts makes this batch zeolitic slurry process greener, resulting in green hydrocarbons and green fuels. [ABSTRACT FROM AUTHOR]

Kraft pulping of wood is based on efficient depolymerization and solubilization of lignin, while cellulose is relatively undamaged. Non-cellulose cell wall polysaccharides are however in some cases heavily degraded, especially pectin and to a lesser degree also glucomannan while, xylan is relatively stable. In this mini-review, the most important reactions in lignin and polysaccharide degradation in kraft pulping are described, both the technically favorable and the problematic reactions, and the chemical background to discuss the advantages and drawbacks of the process. An attempt to put the different reactions in the perspective of the goals of the pulping process is made and a special focus is on the development of color in the pulp fiber during the kraft pulping. [ABSTRACT FROM AUTHOR]

The use of alkaline earth‐abundant metal catalysts as alternatives to transition metal catalysts in the depolymerization of plastic waste is a very important research area. In this work, the first method is described for the conversion of polyesters into value‐added compounds catalyzed by a magnesium catalyst. It is demonstrated that the commercially available, inexpensive and air‐stable, alkaline earth magnesium catalyst Mg(OTf)2 efficiently promotes the reductive depolymerization of several polyesters using pinacolborane (HBpin) as the reducing agent with good to excellent yields. This catalyst also remains very active in at least 12 consecutive polycaprolactone (PCL) reductive depolymerization reactions with yields between 89% and 81%. This magnesium catalyst is also efficient in the reductive depolymerization of the polycarbonate poly(bisphenol A carbonate) (PC.BPA). Furthermore, it is found that Mg(OTf)2 also successfully catalyzes the methanolysis of polyesters and polycarbonates at moderate temperature with excellent yields. [ABSTRACT FROM AUTHOR]

Increasing the efficiency of cellulose hydrolysis is a crucial milestone to enable its use as a platform for the production of renewable chemicals. Consequently, exploring alternative techniques for cellulose dissolution and subsequent depolymerization and hydrolysis remains a pivotal area of research. This study delves into the performance of diverse solid acid catalysts (ion-exchange resins, metal oxides, and zeolites) for cellulose depolymerization when combined with a concentrated solution of zinc chloride (ZnCl2) as the reaction medium and extractant. The influence of this molten salt hydrate on cellulose dissolution and the stability of the tested catalysts was thoroughly investigated. Optimal mild operating conditions (90 °C and 2 h) that facilitate enhanced conversion and selective glucose production were identified. The highest glucose yields (exceeding 40%) were obtained with Amberlyst-15 and HZSM-5 (SiO2/Al2O3 = 23), effectively mitigating product degradation and equaling or surpassing the traditional homogeneous system using H2SO4. Furthermore, insights into the deactivation mechanisms affecting the best catalysts are provided. [ABSTRACT FROM AUTHOR]

The ability to revert polymers to their original monomers represents a crucial chemical recycling technique, promoting sustainability and offering the chance to convert used materials into valuable products. In recent years, numerous studies have explored the use of polymers synthesized via reversible deactivation radical polymerization (RDRP) techniques to facilitate efficient depolymerization reactions. Herein, we report the use of a photocatalyst, zinc tetraphenylporphyrin (ZnTPP), along with light irradiation to accelerate depolymerization of polymers prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization. We explore various parameters affecting depolymerization efficiency, including solvents, reaction temperature (80, 100, and 120°C), the presence of photocatalysts (ZnTPP and Eosin Y), and the type of RAFT end‐groups, namely trithiocarbonate, dithiobenzoate, and 1H‐pyrazole‐1‐carbodithioate. For instance, when PMMA was diluted to 25 mM in 1,4‐dioxane and heated to 120°C under green light irradiation in the presence of ZnTPP (200 ppm), rapid depolymerization exceeding 70% occurred within 1 h. Without ZnTPP, under similar conditions, the reaction required over 8 h to achieve a slightly lower yield. Furthermore, this method confers moderate oxygen tolerance to the system, enabling depolymerization to proceed without the need of deoxygenation, albeit at a lower rate and consequently lesser monomer recovery (31%). [ABSTRACT FROM AUTHOR]

To combat the crisis of today's synthetic polymers arising from unsustainable production and disposal, it is essential for the synthetic polymer community to reshape the current polymer industry with sustainable polymers. As an emerging class of sustainable polymers, the development of chemically depolymerizable polymers (CDPs), which can undergo closed-loop depolymerization/repolymerization cycles to reproduce virgin polymers without the loss of properties from recovered monomers, offers an ideal solution to preserve finite natural resources, provides a feasible solution to the end-of-life issue of polymer waste, and thereby establishes a circular materials economy. However, two grand key challenges have been encountered in the establishment of practically useful CDPs: how to balance polymerization and depolymerization ability and how to unify conflicted depolymerizability and physical properties. Accordingly, this critical review article presents our vision for summarizing feasible strategies to overcome the above two significant challenges and the design principles for constructing an ideal CDP by highlighting selected major progress made in this rapidly expanding field. [ABSTRACT FROM AUTHOR]

Chemical‐to‐bioelectricity by using different biocatalysts was considered as a next‐generation green power source. However, bioelectricity production using macromolecular substrate usually encountered low Coulombic efficiency (CE) and power density due to inefficient electron releasing and sluggish electron collection. Here, a rationally engineered biocascade (including depolymerization module, fermentation module, and electro‐respiration module) embedded in highly conductive 3D graphene hydrogel (electron collection module) was designed and fabricated as a modular platform to simultaneously improve the substrate degradation, enhance the electron releasing and reinforce the electron collection. As a result, this modular platform enabled a ~15‐fold improvement on power density and reached the highest CE (46.3%) and power density (780 mW/m2) ever reported for bioelectricity production from starch (a model macromolecular substrate). This work demonstrated a promising approach for rationally harvesting bioelectricity with complicated substrates, which would open up a new avenue for practical applications. [ABSTRACT FROM AUTHOR]

The global increase in polyethylene terephthalate (PET)-based waste fiber poses a persistent environmental risk. While efforts have been made to repurpose waste fibers into bags, clothing, and building materials, the depolymerization process to extract pure raw materials for recycling remains underdeveloped. This study investigates the impact of normal hexane treatment on the purity of terephthalic acid (TPA) recovered from wastewater containing sodium terephthalate, ethylene glycol, and impurities generated during polyester fabric weight reduction or waste fiber recycling processes. Nuclear magnetic resonance analysis of the recovered TPA (rTPA) revealed a maximum purity of 99.81%, suggesting the effective removal of diverse contaminants such as adhesives and surfactants present in waste fibers through normal hexane and activated carbon treatments. This research contributes to the development of efficient and sustainable PET waste fiber recycling processes, highlighting the potential of normal hexane treatment in enhancing the purity of rTPA.

This study aims to develop alkyd-aldehyde and alkyd-ketone blends by modification of waste poly(ethylene terephthalate) (PET) based alkyd resin with urea-aldehyde (UA) and cyclohexanone formaldehyde (CHF) resins for use in coating applications. PET flakes were depolymerized by simultaneous hydrolysis-glycolysis reaction, and depolymerization product (DP) was used completely instead of the diol in the alkyd synthesis. For comparison, reference alkyds without PET were also synthesized. The effect of modifier resin at different ratios and the presence of DP on the coating and thermal properties of blend films were investigated. Medium-hard/hard and gloss/high gloss films with excellent adhesion and impact resistance were obtained from both blends. These films also demonstrated superior chemical and environmental resistance. Blends with CHF resin had better alkali resistance than those with UA resin. In PET-based blends, thermal resistance significantly increased with the addition of the CHF resin to the alkyd resin. Notably, the use of DP did not show a negative effect on the properties of alkyd resin and blend films. On the contrary, much better results were obtained than the alkyd resin alone. Overall, the modification with UA and CHF modifiers and using DP improved the coating properties of the blends. These blends are expected to be considered a sustainable and environmentally friendly alternative for designing versatile coatings for various applications.

A novel hollow ZIF-8/CdS heterojunction photocatalyst was synthesized to catalyze the cleavage of the C β -O bond of lignin β-O-4 model compounds, and the cleavage rate reached 30.3 ∙mmol∙h−1∙g−1 within 20 min. [Display omitted] Photocatalytic splitting of the C β -O bond is regarded as a prospective strategy for transforming lignin, and it is imperative to develop novel photocatalysts with effective photogenerated charges separation and solar absorption capacity. Herein, a novel hollow ZIF-8/CdS heterostructure photocatalyst was synthesized for the catalytic splitting of lignin C β -O bonds. The photocatalytic cleavage rate of C β -O bond of ligin β-O-4 reached 30.3∙mmol∙h−1∙g−1 within 20 min under visible light exposure. It is noteworthy that the utilization of intricate natural lignin molecules in this photocatalytic system has yielded successful depolymerization. The DFT and XPS results indicate a potential unidirectional electron migration from ZIF-8 to CdS in ZIF-8/CdS composites transfer. This electron transport path follows the direct Z-scheme heterostructure mechanism, resulting in the generation of an internal electric field between ZIF-8 and CdS. Impressively, the synergistic combination of the hollow structure and Z-scheme heterostructure effectively enhances the efficiency of charge carrier separation and maintains a robust redox potential, thereby facilitating C α -radical generation. This study proposes a novel photocatalyst design strategy that integrates hollow structures and Z-scheme heterojunctions, with the aim of targeting the depolymerization of the C β -O bond in lignin. [ABSTRACT FROM AUTHOR]

Hydrogels are of interest for a wide range of applications. The ability to control when the hydrogel degrades can provide beneficial properties such as controlled degradation in the environment or the stimulated release of drugs or cells. Self‐immolative polymers are a class of degradable polymers that undergo complete end‐to‐end depolymerization upon the application of a stimulus. They have been explored for hydrogel development, but the ability to prepare and selectively degrade self‐immolative hydrogels under neutral aqueous conditions has so far been limited. We describe here the preparation of water‐soluble polyglyoxylamides with cross‐linkable pendent azides and their cross‐linking to form hydrogels with 4‐arm poly(ethylene glycol)s having unstrained and strained alkynes using copper‐assisted and strain‐promoted azide‐alkyne click chemistry respectively. The influence of pendent azide density and solution polymer content on the resulting hydrogels was evaluated. A polyglyoxylamide with a 70 : 30 ratio of pendent hydroxyl:azide successfully provided hydrogels with compressive moduli ranging from 1.3–6.3 kPa under copper‐free conditions at 10–20 % (w/w) of polymer in phosphate‐buffered saline. Selective depolymerization and degradation of the hydrogels upon irradiation with light was demonstrated, resulting in reductions in the compressive moduli and the release of depolymerization products that were detected by NMR spectroscopy. [ABSTRACT FROM AUTHOR]