Chemical recycling/upcycling of plastics has emerged as one of the most promising strategies for the plastic circular economy, enabling the depolymerization and functionalization of plastics into valuable monomers and chemicals. However, studies on the depolymerization and functionalization of challenging super engineering plastics have remained in early stage and underexplored. In this review, we would like to discuss the representative accomplishments and mechanism insights on chemical protocols achieved in depolymerization of super engineering plastics, especially for poly(phenylene sulfide) (PPS), poly(aryl ether)s including poly(ether ether ketone) (PEEK), polysulfone (PSU), polyphenylsulfone (PPSU) and polyethersulfone (PES). We anticipate that this review will provide an overall perspective on the current status and future trends of this emerging field.

Chain-growth radical polymerization of vinyl monomers is essential for producing a wide range of materials with properties tailored to specific applications. However, the inherent resistance of the polymer's C―C backbone to degradation raises significant concerns regarding long-term environmental persistence, which also limits their potential in biomedical applications. To address these challenges, researchers have developed strategies to either degrade preexisting vinyl polymers or incorporate cleavable units into the backbone to modify them with enhanced degradability. This review explores the various approaches aimed at achieving backbone degradability in chain-growth radical polymerization of vinyl monomers, while also highlighting future research directions for the development of application-driven degradable vinyl polymers.

As a powerful synthetic tool, ruthenium-catalyzed ring-opening metathesis polymerization (ROMP) has been widely utilized to prepare diverse heteroatom-containing polymers. In this contribution, we report the synthesis of the novel imine-based polymer through the copolymerization of cyclooctene with cyclic imine comonomer via ROMP. Because of the efficient hydrolysis reactions of the imine group, the generated copolymer can be easily degraded under mild condition. Moreover, the generated degradable product was the telechelic polymer bearing amine group, which was highly challenged for its direct synthesis. And this telechelic polymer could also be used for the further synthesis of new polymer through post-transformation. The introduction of imine unit in this work provides a new example of the degradable polymer synthesis.

Poly(L-lactide) (PLLA) is one of the best candidates as a bio-based plastic material for circular economy because of its biodegradability, sustainability, recyclability, and good thermal and mechanical properties. The industrial production of PLLA is mainly from tin(II) 2-ethylhexanoate [Sn(Oct)₂]-catalyzed ring-opening polymerization (ROP) of L-LA in melt and bulk conditions at high temperatures (150−200 °C). Despite the huge efforts devoted to the development of organometallics with low toxicity and many highly active catalysts under mild laboratory conditions, very few candidates can compete with Sn(Oct)₂ under industrially relevant conditions. Herein, we report novel zinc complexes bearing phenylimino-pyridine-phenolate ligands as efficient catalysts for L-LA polymerization under both mild and industrially relevant conditions, with a turnover frequency as high as 6200 h⁻¹. The best performing catalyst competed well with Sn(Oct)₂ under industrial conditions and afforded colorless and semicrystalline PLLA. In addition, preliminary depolymerization experiments suggested that the new catalysts can also be used for the chemical recycling of commercial PLLA directly to L-LA with high selectivity under bulk and melt conditions.

Most commercial plastics cannot easily degrade, which raises a number of sustainability issues. To address the current problem of plastic pollution, the research and development of easily degradable and recyclable polymers has become an attractive subject. Herein, a new monomer of thiosalicylic methyl glycolide (TSMG) was synthesized using one-pot method and high molecular weight poly(thiosalicylic methyl glycolide) (PTSMG, M_n up to 300 kDa) can be obtained via the ring-opening polymerization (ROP) of TSMG. PTSMG exhibits good closed-loop recyclability and hydrolytic degradability, where PTSMG can generate pristine monomers through sublimation thermal depolymerization conditions due to the presence of thiophenol ester bond in the polymer chains, and can be degraded rapidly in aqueous solution, which provides a potential solution to the current plastic pollution problem.

The development of degradable and chemically recyclable polymers is a promising strategy to address pressing environmental and resource-related challenges. Despite significant progress, there is a need for continuous development of such recyclable polymers. Herein, PPDO-PLLA-PU copolymers were synthesized from poly(p-dioxanone)-diol (PPDO-diol) and poly(L-lactide)-diol (PLLA-diol) by chain extension reaction. The chemical structures and microphase structures of PPDO-PLLA-PU were characterized, and their crystalline properties, mechanical properties, and degradation behaviors were further investigated. Significantly, the distribution of PLLA phase in the copolymer matrix showed a rod-like microstructure with a slight orientation, despite the thermodynamic incompatibility of PPDO and PLLA segments. Moreover, on the basis of this microphase separation, PPDO spherulites can crystallize using the interface of the two phases as nucleation sites. Accordingly, the combined effect of above two contributes to the enhanced mechanical properties. In addition, PPDO-PLLA-PU copolymers have good processability and recyclability, making them valuable for a wide range of applications.

The asymmetric alternating copolymerization of meso-epoxide and cyclic anhydrides provides an efficient access to enantiopure polyesters. Contrary to the extensive investigation of the stereochemistry resulting from epoxide building block, the chirality from anhydride and the configurational match with epoxide remain elusive. Herein, we discover that the bimetallic chromium catalysts have led to an obvious enhancement in terms of reactivity and enantioselectivity for the asymmetric copolymerization of meso-epoxide with various non-symmetric chiral anhydrides. Up to 97% ee was obtained during the asymmetric copolymerization of cyclohexene oxide (CHO) with (R)-methylsuccinic anhydride (R-MSA), and three- or four-carbon chiral centers were simultaneously installed in the aliphatic polyester backbone. In particular, the different combinations of stereochemistry in epoxide and anhydride building blocks considerably affect the thermal properties and crystalline behaviors of the resulting polyesters. This study uncovers an interesting method for regulating polymer crystallinity via matching the chirality of different monomers.

Incorporating a low density of ester units into the backbone of polyethylene materials enhances their sustainability and recyclability while maintaining the main material properties of polyethylenes. Here we report a new way to access degradable polyethylene materials with a low content of in-chain ester units via mechanochemical backbone editing. Initially, ester groups are incorporated as side groups through catalytic copolymerization of ethylene with a cyclobutene-fused lactone monomer (CBL), yielding polyethylene materials with high molecular weights and adjustable thermomechanical properties. Subsequent solid-state ball-milling treatment selectively introduces side-chain ester groups into the main chain of the polyethylene materials via force-induced cycloreversion of the cyclobutane units. Under acidic conditions, hydrolysis of the resultant polyethylene materials with in-chain ester units facilitates further degradation into oligomers.

Chemical modification of polymers represents a pivotal method for achieving functionalized polymer materials. However, due to the lack of post-functional handle, the chemical modification of polyester materials remains a significant challenge. Ring-opening copolymerization of cyclic anhydride and epoxides is a powerful approach to synthesize polyesters. In this work, we for the first time demonstrate the functionalizability of polyesters synthesized with brominated anhydride monomers. The post-functionalization is amenable to a wide variety of reactive groups and reactions with high yields. With multiple well-established functionalization pathways of brominated polyester materials and optimized the conditions for the modification reactions, a series of functionalized polyester materials can be obtained with high yields, providing new insights for the research about functionalization of polymers.

Incorporation of acetal groups in the backbone is a potent strategy to create polymers that are cleavable or degradable under acidic conditions. We report here an in-depth study on the ring-closing-opening copolymerization of o-phthalaldehyde (OPA) and epoxide using Lewis pair type two-component organocatalysts for producing acetal-functionalized polyether and polyurethane. Notably, triethylborane as the Lewis acid, in comparison with tri(n-butyl)borane, more effectively enhances the polymerization activity by mitigating borane-induced reduction of the aldehyde group into extra initiating (borinic ester) species. Density functional theory (DFT) calculations present comparable energy barriers of OPA-epoxide cross-propagation and epoxide self-propagation, which is consistent with the experimental finding that an alternating-rich copolymer comprising mostly OPA-epoxide units but also epoxide-epoxide linkages is produced. In particular, when epoxide is added in a large excess, the product becomes a polyether containing acetal functionalities in the central part of the backbone and thus being convertible into polyurethane with refined acid degradability.

Chemically recyclable polythioesters are of particular interest owing to their unique properties and desired sustainability. By the exploit of a benzo-fusion strategy to ε-thiocaprolactone, we successfully improved the chemical recyclability and regulated the thermal and mechanical properties of the resulting polythioesters. The efficient ring-opening polymerization (ROP) of benzo-fused thiolactone monomers (M) containing different substituents gave rise to high-molecular-weight semi-aromatic polythioesters P(M)s. The resulting P(M)s showcased tunable physical and mechanical properties. The debenzylation of P(M3) was able to generate P(M3-OH) with free hydroxyl sidechains. Notably, chemical recycling of the resulting P(M)s back to their corresponding monomers via bulk thermal depolymerization achieved high efficiency (>95% yield, 99% purity), establishing a closed-loop lifecycle.

Poly(lactic acid) (PLA), a bio-based polymer, is considered to be a sustainable alternative to conventional petroleum-based plastics. However, owing to its widespread use and relatively slow degradation rate in water, PLA still poses potential environmental pollution risks after being discarded. The efficient chemical recycling of PLA represents an attractive approach to addressing both resource reuse and environmental pollution challenges caused by its waste. Hydrolysis is the predominant method of industrial recycling. However, because PLA is insoluble in water, efficient heterogeneous hydrolysis requires high-temperature and high-pressure conditions. In this study, an efficient homogenous hydrolysis method capable of simultaneously dissolving PLA and calcium hydroxide (Ca(OH)₂) was developed. Suitable solvents for this method were screened, and it was found that PLA hydrolysis using dioxane and 1,4,7,10,13-Pen-taoxacyclopentadecane as solvents achieved conversion rates of 93% and 90%, respectively, within 2 h at room temperature. Notably, the hydrolysis product, calcium lactate, precipitated as a solid from the solvent and therefore self-separated from the reaction solution. The solvent, acid/base conditions, water content, and depolymerization kinetics were investigated. Compared with previously reported hydrolysis methods, the enhanced efficiency observed in this study can be attributed to the concurrent solvation of PLA and Ca(OH)₂, which maintains homogeneity throughout the reaction process. Additionally, this method facilitates closed-loop recycling of PLA and is compatible with the highly selective recovery of PLA from various types of PLA products.

The asymmetric molecular design strategy, with advantages in modulating the molecular dipole moment and intermolecular interactions and achieving more favorable molecular packing and orientation, has been an effective approach for designing high-performance non-fullerene acceptors (NFAs). Herein, two asymmetric NFAs, Y-CN-2F and Y-CN-2Cl, were designed and synthesized by introducing a linear alkyl chain terminated with the 4-cyanobiphenyl group, a well-known mesogenic unit, at one of the inner pyrrole positions instead of the normal 2-butyloctyl branched alkyl chain. The difference between Y-CN-2F and Y-CN-2Cl is the terminated IC-groups, which was modified with F and Cl halogens, respectively. Both NFAs displayed strong absorption in the near-infrared to visible-light range, which is complementary to that of typical medium-bandgap donor polymers. After optimization with D18 donor in organic solar cells (OSCs), Y-CN-2F and Y-CN-2Cl provided comparable power conversion efficiencies (PCEs) of 15.33% and 15.88%. While the D18:Y-CN-2F based devices displayed higher fill factors (FFs), those based on D18:Y-CN-2Cl exhibited higher current densities and open-circuit voltages. The Y-CN-2Cl film showed longer light absorption than Y-CN-2F, which is beneficial for more light harvesting. Moreover, D18:Y-CN-2Cl displayed a lower fluorescence lifetime and faster carrier transfer processes, which could be attributed to its higher mobility. For the D18:Y-CN-2F blended film, a more pronounced fiber network structure and balanced carrier mobility were observed, which contributed to the higher FFs values. This work presents new efforts to develop more asymmetric NFAs with specific functional segments for efficient organic electronics.

Gas-liquid interfacial films have emerged as versatile materials for surface modification in biomedical applications, agriculture, and antifouling owing to their strong substrate-bonding capabilities. Silk nanofibrils (SNF), as nanoscale building blocks of silk, exhibit exceptional mechanical stability, high crystallinity, and aqueous adaptability, making them ideal candidates for fabricating interfacial films. However, conventional fabrication methods for SNF- or protein-based interfacial films often involve complex and resource-intensive chemical processes. To overcome these challenges, this study introduces a simple and efficient strategy for preparing thermally induced SNF gas-liquid interfacial films via heat treatment, leveraging thermal evaporation-induced concentration to drive self-assembly. The method demonstrated broad applicability to various proteins and hydrophilic substrates, offering versatility and sustainability. Furthermore, the prepared films exhibited potential as antifouling and anti-counterfeiting functional coatings, significantly expanding the application scenarios of protein-based interfacial films.

Bioinspired active pillar structures, known for their large surface area, mechanical compliance, and diverse deformation modes, have garnered extensive research interest. Among various active pillar structures, liquid crystal elastomer (LCE) pillar arrays are capable of exhibiting significant and reversible anisotropic deformation under cyclic heating and cooling, showing great potential in tunable adhesion, soft robots, and biomedical devices. However, scaling up LCE pillar manufacturing remains challenging, limiting its practical applications. In this work, a solvent-free LCE resin is developed with unique features including simple operating procedure, short fabrication time, and tunable responsive temperature, enabling rapid and large-scale production of LCE pillar arrays. The LCE resin allows for the preparation of complex 3D shapes in addition to film or specimen. The fabrication time can be as short as 4 h, without the need to evaporate solvent. Moreover, the LCE resins can be adjusted with a variable phase transition temperature range from 49.4 °C to 97.7 °C by incorporating non-liquid crystal acrylate chains. The resulting active pillar array structure can undertake sequential actuation upon heating with the tunable actuation temperature. Finally, the application of these pillar arrays in multi-level information encryption is demonstrated. The LCE pillar structure introduced here offers a new strategy for constructing advanced active LCE structures with tunable responsive behavior.

Functional superhydrophobic coatings have attracted considerable attention because of their potential for a wide range of applications. In this study, a novel cyclotetrasiloxane-based hybrid superhydrophobic modifier (F-D₄) was prepared for the first time using a mild thiol-ene click reaction of 2,4,6,8-tetravinyl-2,4,6,8-tetramethylcyclotetrasiloxane (Vi-D₄) with perfluorohexylethanethiol (PFOT) and mercaptopropyltrimethoxysilane (MPTMS) as the raw materials. Then, F-D₄ was introduced into the fabric via a sol-gel process, resulting in a superhydrophobic fabric (F-D₄-Fabric). The surface characteristics of the modified fabric were determined using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and water contact angle (WCA). The coated fabrics have outstanding mechanical, physical, and chemical stability, and exhibit excellent self-cleaning and anti-fouling properties. Owing to its superhydrophobicity, F-D₄-Fabric could efficiently separate a range of oil/water mixtures with a separation efficiency of up to 99.99%. The study showed that the modification strategy used in the dip-coating process greatly affected the superhydrophobicity of the cotton fabric, which is useful for oil/water separation and self-cleaning applications.

Polydopamine-based melanin-like materials have been widely used in the fields of ultraviolet (UV) shielding, solar desalination and anti-inflammatory treatment owing to their unique physical properties. The well-established synthesis of polydopamine nanoparticles involves the oxidative polymerization of dopamine-derived monomers, resulting in cross-linked nanostructures with high complexity and heterogeneity. Therefore, the controlled synthesis of polydopamine-based melanin-like materials with well-defined structures and predictable properties remains challenging. Herein, we propose a mechanochemical Suzuki polymerization approach for the synthesis of linear melanin-like polymers with tunable physical properties. Compared with polydopamine nanoparticles, the mechanochemical approach offers a more flexible chain-like structure, thereby enhancing its antioxidant performance. Furthermore, this approach also enables the preparation of a melanin-like alternating copolymer that exhibits green fluorescence owing to its π-conjugated structure. This study not only offers opportunities for exploring novel synthetic melanin materials, but also provides new insights into the structure-function relationships of polydopamine-based materials.

Living cationic polymerization of 4-acetoxystyrene (STO) was conducted in CH₂Cl₂ at ‒15 °C using a dicumyl chloride (DCC)/SnCl₄/n-Bu₄NBr initiating system. Impurity moisture initiation was inhibited by adding proton trap 2,6-di-tert-butylpyridine (DTBP), and the controlled initiation of DCC was confirmed by ¹H nuclear magnetic resonance (¹H-NMR) spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass (MALDI-TOF-MS) spectrometry. The polymerization kinetics were analyzed to for optimizing the polymerization rate. Allyl-telechelic PSTOs (allyl-PSTO-allyl) with molecular weight (M_n) range of 3540–7800 g/mol and narrow molecular weight dispersity (M_w/M_n) about 1.25 were prepared through nucleophilic substitution with allyltrimethylsilane (ATMS) at approximately 40% monomer conversion. The experimental results indicate that the substitution efficiency of ATMS increased with higher ATMS concentration, temperature, and extended reaction time. Nearly unity ally-functionality for allyl-PSTO-allyl was achieved by adding sufficient SnCl₄ prior to the substitution.

Enhancing the lubricating properties and antibacterial adhesion resistance of implantable medical materials is critical to prevent soft tissue injury during implantation and the formation of bacterial biofilms. Prior studies may have exhibited limitations in the preparation methodologies and long-term stability of coatings for implantable medical materials. In this study, we developed a multilayered hybrid hydrogel coating method based on the rate difference of polymerization initiation on the material surface. The acquired coating with persistent lubrication capability retained its functionality after 2×10⁴ cycles of friction and 21 days of PBS immersion. A quaternary ammonium salt coating with antibacterial properties was introduced to further functionalize the coating. Animal experiments demonstrated that this coating exhibited remarkable effects on delaying encrustation and bacterial colonization. These studies indicate that this simple method of introducing lubricating and antibacterial coatings on catheters is likely to enhance the biocompatibility of medical devices and has broad application prospects in this field of medical devices.

A significant challenge in developing block copolymer photonic crystals is constructing low-symmetric ordered phases, which are essential for achieving a complete photonic band gap. Here, we propose a promising strategy to create low-symmetric ordered morphologies by incorporating shape-anisotropic rod-like side chains into block copolymers. Using dissipative particle dynamics simulations, we demonstrate that block copolymers with longer rod-like side chains can self-assemble into a hexagonally packed columnar phase characterized by a low-symmetric rectangular cross-section. Photonic band structure calculations reveal that this low-symmetric columnar phase can exhibit a complete photonic band gap, with the gap size dependent on the aspect ratio of the rectangular cross-sections of the columns. Our findings suggest an effective approach to constructing low-symmetric photonic crystals through the self-assembly of block copolymers with shape-anisotropic segments.