Controlled-Radical Polymerization of α-Lipoic Acid: A General Route to Degradable Vinyl Copolymers

Versatile Solid-State Medical Superglue Precursors of α-Lipoic Acid

α-Lipoic acid (αLA) is an attractive building block for medical adhesives. However, due to poor water solubility of αLA and high hydrophobicity of poly(αLA), elevated temperatures, organic solvents, or complex preparations are typically required to obtain and deliver αLA-based adhesives to biological tissue. Here, we report αLA-based powder and low-viscosity liquid superglues that polymerize and bond rapidly upon contact with wet tissue. A monomeric mixture of αLA, sodium lipoate, and an activated ester of lipoic acid was used to formulate the versatile adhesives. Stress-strain measurements of the wet adhesives confirmed the high flexibility of the adhesive. Moreover, a small molecule regenerative drug was successfully incorporated into and released from the adhesive without altering the physical and adhesive properties. In vitro and in vivo studies of the developed adhesives confirmed their cell and tissue compatibility, biodegradability, and potential for sustained drug delivery. Moreover, due to the inherent ionic nature of the adhesives, they demonstrated high electric conductivity and sensitivity to deformation, allowing for the development of a tissue-adherent strain sensor.

GSH/pH-sensitive Förster resonance energy transfer nanoparticles for synergistic chemotherapy and chemodynamic therapy

Stimulus-responsive polymers have attracted significant attention as intelligent and advanced drug delivery systems. In this work, a glutathione-responsive polymer was synthesized by reversible addition-fragmentation chain transfer polymerization of natural biological molecules lipoic acid and tetraphenylene (TPE)-containing vinyl monomers. The poly(disulfide) block ensures rapid degradation of carriers and drug release under specific conditions. In addition, the introduction of pendant carboxyl groups enables Fe3+ incorporating capacity and the hydrophobic TPE block significantly boosts drug loading and aggregation induced emission (AIE) for visualization of assembly. Fe3+ and doxorubicin (DOX) loaded nanoparticles (DOX@Fe NPs) were obtained via coordination and hydrophobic interactions for synergistic chemodynamic therapy and chemotherapy. Especially, the Förster resonance energy transfer (FRET) between TPE and DOX further enables visualization of DOX release via a fluorescence signal. The in vitro release experiment results demonstrated that under the conditions of pH 5.5 and 5 mM GSH, the release efficiency of DOX reached 79.2% in 12 hours. In the cellular experiment, the viability of 4T1 cells co-incubated with DOX@Fe NPs for 48 hours was only 2.5%, verifying that DOX@Fe NPs possess potent tumor-killing capability.

UV-Responsive Adhesive Based on Polystyrene-block-Poly(Ethyl Lipoate) Copolymer

Block copolymers (BCPs), capable of self-assembling into various nanoscale structures, are widely used in adhesives owing to their versatile properties. However, conventional BCP-based adhesives pose environmental concerns: they are petroleum-derived, non-degradable, and have a non-tunable adhesion strength. To address these challenges, a novel BCP is designed comprising a conventional hard segment, polystyrene (PS), and a green rubbery segment, poly(ethyl lipoate) (PEtLp), derived from the bio-based molecule α-lipoic acid. The PS-b-PEtLp is synthesized via the base-catalyzed ring-opening polymerization from thiol-terminated PS. Adhesion tests showed that PS-b-PEtLp with cylindrical nanostructures exhibited higher adhesion strength than that with lamellar structures. Importantly, the dynamic disulfide bonds in PEtLp enable a reversible and adjustable adhesion strength under UV light. Upon UV irradiation, the adhesion strength decreases by approximately half, facilitating easy separation from the adherends. Additionally, the selective depolymerization of the PEtLp block achieves 100% conversion, enabling the recovery of the monomer (EtLp) and macroinitiator (thiol-terminated PS). This study introduces a sustainable, degradable, and reusable adhesive derived from renewable resources, providing a promising solution to the environmental challenges associated with traditional petroleum-based adhesives.

Modular Access from Acrylate to a Sustainable Polyester Platform with Large-Span Tunability and Chemical Circularity under Mild Conditions

Making polyesters with conventional vinyl monomers is one of the most economical ways to develop sustainable polymeric materials. For polar vinyls, while their transformation into lactones has been studied extensively, there exists no further access to synthesizing polyesters, presumably due to the nonstrained and nonpolymerizable nature of the obtained lactones. Herein, we report the first facile synthesis of polyesters that originated from one of the most critical classes of polar vinyls-acrylates. Specifically, a series of modular six-membered lactones were rationally designed and synthesized from methyl acrylate together with malonic esters containing diverse functional groups and formaldehyde. The monomers underwent ring-opening polymerization (ROP) to yield the first acrylate-derived polyesters, which further constitute a unique polymer platform with a large scope of potential functionalities and performances as well as easy chemical circularity under mild conditions. Notably, the obtained polyesters are a rare example featuring tunable functionalities on the side ester groups whose impact on certain material properties (e.g., glass transition temperature) is similar to that of polyacrylates, implying potential replacement between polyesters and polyacrylates. In addition, by presenting the special geminal disubstitutions originally from the monomers' γ-position for the first time, polyesters also exhibited unprecedentedly enhanced thermal and recycling properties: Variation of the geminal disubstitutions offers a unique access to large-span modulation from completely amorphous to high-level crystalline materials, and the melting temperature of the polymer with high crystallinity was drastically increased by 84 °C compared with the reported monosubstituted counterpart. At the same time, compared with polyesters synthesized from other six-membered lactones whose chemical recycling required harsh conditions (>150 °C and high vacuum), the gem-disubstituted polyesters in this work can undergo complete chemical recycling to monomers under much milder conditions (80 °C and ambient pressure). This study informs the design of future high-performance polyesters derived from polar vinyls.

Degradable Adhesives as Sustainable Alternatives to Acrylics via Ring-Opening Radical Polymerization of Vinylcyclopropanes

Acrylic pressure-sensitive adhesives (PSAs) are loosely crosslinked polymer networks widely used across various industries. However, the network structure and inert nature of the acrylic polymer backbone present sustainability challenges. To address these issues, efforts are being made to incorporate degradable units into the polymer backbone. Yet, two key obstacles remain: i) the polymer does not degrade into sufficiently small fragments, and ii) the adhesive and viscoelastic properties are often inferior to those of conventional acrylic polymers. In this study, we developed a PSA utilizing vinylcyclopropane (VCP)-based monomers and a VCP-based crosslinker, achieving molecular-level degradation while maintaining adhesive performance and viscoelastic properties comparable to traditional acrylic PSAs. Under optimized polymerization conditions, the polymer incorporates ozone-labile double bonds into its backbone, enabling controlled molecular degradation without compromising its properties. By synthesizing and strategically combining various VCP-based monomers, we developed PSAs with tailored adhesion and viscoelastic behavior on par with conventional acrylic PSAs. These advancements indicate that the degradable polymers and PSAs developed in this study are poised for practical application in the near future.

Synthesis of novel chalcone/lipoic acid derivatives and cross-linked chitosan for preparation of multi-functional packaging film

Chitosan is a bio-based material that is more environmentally friendly than traditional petroleum-based materials, but its biofilms often suffer from brittleness and limited antioxidant and antibacterial properties. To overcome these challenges, chemically modified chitosan is a key solution. Herein, a novel CS-LA/CHA films were prepared through a radical reaction of chitosan (CS), lipoic acid/chalcone derivative (LA/CHA) and N,N-methylene bisacrylamide (MBA). Experimental results indicate that the tensile strength of the CS-LA/CHA film is 65 % greater than that of the standard chitosan film following radical cross-linking modification. Additionally, the chalcone ester structure elevates the water contact angle of the CS-LA/CHA film by 18 %, and its antioxidant activity improves to 81 ± 0.01 % (p < 0.01). Concurrently, the water absorption rate (WA) and water vapor permeability (WVP) exhibited significant reductions. Given the remarkable antibacterial properties of chalcone, the CS-LA/CHA film effectively inhibits the proliferation of Escherichia coli and Staphylococcus aureus, which containing 15 wt% LA/CHA can kill >94.1 ± 0.09 % (p < 0.01) of S. aureus and 98.1 ± 0.07 % (p < 0.01) of E. coli. Furthermore, this film can extend the shelf life of fish by an additional 6 to 8 days. The CS-LA/CHA film exhibits substantial potential for application in food preservation.

Responsive Degradable Bottlebrush Polymers Enable Drugs With Superior Efficacy and Minimal Systemic Toxicity

Bottlebrush polymers (BBPs) have garnered significant attention as advanced drug delivery systems, capable of transporting a diverse range of therapeutic agents, including both chemical drugs and biologics. Despite their effectiveness, the empty BBP vectors post-drug release may pose long-term safety risks due to their difficult systemic clearance. Here, a responsive degradable BBP platform for cancer therapy is developed, featuring a poly(disulfide) backbone grafted with fluorine-terminated zwitterionic side chains. Anti-cancer drugs are tethered to the backbone via a clinically approved valine-citrulline (VC) linker. This design leverages the tumor's reductive environment and Cathepsin B overexpression for BBP rapid degradation and precise drug release restricted within tumor cells, thereby addressing systemic safety concerns over synthetic BBP and expanding the therapeutic window of anti-cancer drugs simultaneously. Surface fluorination of BBP further enhances tumor accumulation and deep penetration. In vivo studies with monomethyl auristatin E (MMAE)-loaded BBP in tumor-bearing mice demonstrate substantial tumor suppression with minimal side effects. Together, these findings highlight the potential of responsive degradable BBP as a versatile unimolecular platform for cancer drug delivery, addressing existing challenges associated with synthetic BBP nanomedicines.

Versatile and Controlled Synthesis of Degradable, Water-Soluble Bottlebrush Polymers with Poly(disulfide) Backbones Derived from α-Lipoic Acid

Bottlebrush (BB) polymers, with their densely grafted side chains and unique architecture, are highly advantageous for drug delivery due to their high functional group density for drug conjugation, unimolecular nature, and enhanced biodistribution properties. These attributes enable extended blood circulation half-life, improved tumor tissue penetration, and high tumoral drug accumulation. However, the typically nondegradable, all-carbon backbones of most BB polymers limit their suitability for applications requiring controlled clearance and biodegradability. To address this, we developed degradable BB polymers with poly(disulfide) backbones synthesized via reversible addition-fragmentation chain transfer (RAFT) copolymerization of α-lipoic acid (LA), a renewable and readily available compound, with acrylate-based inimers. These copolymers feature degradable backbones and initiating sites for subsequent BB synthesis. Using an atom transfer radical polymerization (ATRP) grafting-from methodology, we synthesized BB polymers with relatively low dispersities (Đ = 1.30-1.53), high backbone degrees of polymerization (DPbb), and high molar masses (Mn,MALS = 650-2700 kg/mol). The easily cleavable disulfide bonds enabled backbone degradation under mild reducing conditions. Beyond hydrophilic BB with tri(ethylene glycol) methyl ether acrylate (TEGA) side chains, we synthesized BB with cationic, anionic, and zwitterionic side chains, demonstrating broad monomer compatibility. This scalable approach produces water-soluble, degradable BB polymers with tunable architectures and predictable molecular weights. By addressing the need for degradability in BB polymers, this work advances their potential for drug delivery, offering enhanced functionality, biocompatibility, and sustainability.

Radical Ring-Opening Polymerization: Unlocking the Potential of Vinyl Polymers for Drug Delivery, Tissue Engineering, and More

Synthetic vinyl polymers have long been recognized for their potential to be utilized in drug delivery, tissue engineering, and other biomedical applications. The synthetic control that chemists have over their structure and properties is unmatched, allowing vinyl polymer-based materials to be precisely engineered for a range of therapeutic applications. Yet, their lack of biodegradability compromises the biocompatibility of vinyl polymers and has held back their translation into clinically used treatments for disease thus far. In recent years, radical ring-opening polymerization (rROP) has emerged as a promising strategy to render synthetic vinyl polymers biodegradable and bioresorbable. While rROP has long been touted as a strategy for preparing biodegradable vinyl polymers for biomedical applications, the translation of rROP into clinically approved treatments for disease has not yet been realized. This review highlights the opportunities for leveraging rROP to render vinyl polymers biodegradable and unlock their potential for use in biomedical applications.

Versatile Light-Mediated Synthesis of Degradable Bottlebrush Polymers Using α-Lipoic Acid

Bottlebrush polymers have a variety of useful properties including a high entanglement molecular weight, low Young's modulus, and rapid kinetics for self-assembly. However, the translation of bottlebrushes to real-world applications is limited by complex, multi-step synthetic pathways and polymerization reactions that rely on air-sensitive catalysts. Additionally, most bottlebrushes are non-degradable. Herein, we report an inexpensive, versatile, and simple approach to synthesize degradable bottlebrush polymers under mild reaction conditions. Our approach relies on the "grafting-through" polymerization of α-lipoic acid (LA)-functionalized macromonomers. These macromonomers can be polymerized under mild, catalyst-free conditions, and due to reversibility of the disulfide bond in LA, the resulting bottlebrush polymers can be depolymerized by cleaving disulfide backbone bonds. Bottlebrushes with various side-chain chemistries can be prepared through the atom transfer radical polymerization (ATRP) of LA-functionalized macromonomers, and the backbone length is governed by the macromonomer molecular weight and solvent polarity. We also demonstrate that LA-functionalized macromonomers can be copolymerized with acrylates to form degradable bottlebrush networks. This work demonstrates the preparation of degradable bottlebrush polymers with a variety of side-chain chemistries and provides insight into the light-mediated grafting-through polymerization of dithiolane-functionalized macromonomers.

Sustainable and Recyclable Acrylate Resins for Liquid-Crystal Display 3D Printing Based on Lipoic Acid

The development of renewable vinyl-based photopolymer resins offers a promising solution to reducing the environmental impact associated with 3D printed materials. This study introduces a bifunctional lipoate cross-linker containing a dynamic disulfide bond, which is combined with acrylic monomers (n-butyl acrylate) and conventional photoinitiators to develop photopolymer resins that are compatible with commercial stereolithography 3D printing. The incorporation of disulfide bonds within the polymer network's backbone imparts the 3D printed objects with self-healing capabilities and complete degradability. Remarkably, the degraded resin can be fully recycled and reused for high-resolution reprinting of complex structures while preserving mechanical properties that are comparable to the original material. This proof-of-concept study not only presents a sustainable strategy for advancing acrylate-based 3D printing materials, but also introduces a novel approach for fabricating fully recyclable 3D-printed structures. This method paves the way for reducing the environmental impact while enhancing material reusability, offering significant potential for the development of eco-friendly additive manufacturing.

Scalable Synthesis of Degradable Copolymers Containing α-Lipoic Acid via Miniemulsion Polymerization

A robust method is described to synthesize degradable copolymers under aqueous miniemulsion conditions using α-lipoic acid as a cheap and scalable building block. Simple formulations of α-lipoic acid (up to 10 mol %), n-butyl acrylate, a surfactant, and a costabilizer generate stable micelles in water with particle sizes <200 nm. The ready availability of these starting materials facilitated performing polymerization reactions at large scales (4 L), yielding 600 g of poly(n-butyl acrylate-stat-α-lipoic acid) latexes that degrade under reducing conditions (250 kg mol-1 → 20 kg mol-1). Substitution of α-lipoic acid with ethyl lipoate further improves the solubility of dithiolane derivatives in n-butyl acrylate, resulting in copolymers that degrade to even lower molecular weights after polymerization and reduction. In summary, this convenient and scalable strategy provides access to large quantities of degradable copolymers and particles using cheap and commercially available starting materials.

Degradable polyolefins prepared by integration of disulfides into metathesis polymerizations with 3,6-dihydro-1,2-dithiine

Disulfide-containing polyolefins were synthesized by ring-opening metathesis polymerization (ROMP) of the 6-membered disulfide-containing cyclic olefin, 3,6-dihydro-1,2-dithiine, which was prepared by ring-closing metathesis of diallyl disulfide. This approach facilitated the production of disulfide-containing unsaturated polyolefins as copolymers with disulfide monomer units embedded within a poly(cyclooctene) or poly(norbornene) framework. The incorporation of disulfides into the polymer backbone imparts redox responsiveness and enables polymer degradation via chemical reduction or thiol-disulfide exchange. This ROMP copolymerization strategy yielded both linear polyolefins, as well as bottlebrush polymers, with degradable segments, thereby broadening the scope of responsive polymer architectures synthesized by ROMP.

An Expedient Route to Bio-Based Polyacrylate Alternatives with Inherent Post-Chemical Modification and Degradation Capabilities by Organic Catalysis for Polymerization of Muconate Esters

The quest for polymers that would be at the same time bio-based and degradable after usage, in addition to offering chemical post-modification options, remains a daunting challenge in contemporary polymer science. Despite advances in polymer chemistry, attempts at controlling the chain-growth polymerization of muconate esters remain unexplored. Here we show that dialkyl muconates can be rapidly polymerized by organocatalyzed group transfer polymerization (O-GTP). O-GTP is conducted to completion at room temperature in toluene within a few minutes, using 1-ethoxy-1-(trimethylsiloxy)-1,3-butadiene (ETSB) as initiator and 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-phosphoranylidenamino]-2 λ ${\lambda }$ 5,4 λ ${\lambda }$ 5 catenadi(phosphazene) (P4-t-Bu) as catalyst. Chain extension experiments and synthesis of all muconate-type block copolymers can also be achieved. Furthermore, polymuconates are amenable to facile post-polymerization modification reactions. This is showcased through the hydrolysis of the ester side chains leading to well-defined poly(muconic acid), and by epoxidation of the C=C double bonds of the main chain. Last but not least, these internal alkene groups can be selectively cleaved by ozonolysis, demonstrating the upcyclability of polymuconates under oxidative conditions. This work demonstrates that polymuconates constitute a unique platform of bio-based polymers, easily modifiable in addition to being chemically degradable under user friendly experimental conditions.

Biomass-Derived Optically Clear Adhesives for Foldable Displays

Novel acrylate monomers, derived from terpenes are synthesized for use in optically clear adhesives (OCAs) suitable for foldable displays. These OCAs are prepared using visible-light-driven polymerization, an eco-friendly method. Through physical, rheological, and mechanical characterization, the prepared OCAs possess low modulus and exhibit outstanding creep and recovery properties, making them suitable for foldable devices.

Recyclable surgical, consumer, and industrial adhesives of poly(α-lipoic acid)

Polymer adhesives play an important role in many medical, consumer, and industrial products. Polymers of α-lipoic acid (αLA) have the potential to fulfill the need for versatile and environmentally friendly adhesives, but their performance is plagued by spontaneous depolymerization. We report a family of stabilized αLA polymer adhesives that can be tailored for a variety of medical or nonmedical uses and sustainably sourced and recycled in a closed-loop manner. Minor changes in monomer composition afforded a pressure-sensitive adhesive that functions well in dry and wet conditions, as well as a structural adhesive with strength equivalent to that of conventional epoxies. αLA surgical superglue successfully sealed murine amniotic sac ruptures, increasing fetal survival from 0 to 100%.

Sustainable polymers that stick inside and out

A naturally occurring fatty acid yields a set of adhesives with different properties.

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.

New Chemistries for Degradable Pressure-Sensitive Adhesive Networks

With the increasing use of pressure-sensitive adhesives (PSAs) in various industries, there is a need for greater sustainability, particularly in developing polymer materials from renewable resources, as well as the reuse and recycling of materials to reduce environmental impact, reduce waste, or extend their life. Here, we outlined the required properties of PSAs which are governed by the molecular parameters (molecular weights, dispersities, molecular weight between entanglement, molecular weight between cross-links and gel content) of polymer materials which subsequently define the physical properties (storage and loss moduli, glass transition temperature) that are required for good performance in peel, tack and shear tests. The sustainable approach discussed here is the development of degradable polymer materials featuring selectively degradable linkages in the backbone. This provides a viable alternative for the design of PSAs that could overcome the 'stickies' problem and make the recycling of glass and cardboard more efficient.

Defining Reactivity-Deconstructability Relationships for Copolymerizations Involving Cleavable Comonomer Additives

The incorporation of cleavable comonomers as additives into polymers can imbue traditional polymers with controlled deconstructability and expanded end-of-life options. The efficiency with which cleavable comonomer additives (CCAs) can enable deconstruction is sensitive to their local distribution within a copolymer backbone, which is dictated by their copolymerization behavior. While qualitative heuristics exist that describe deconstructability, comprehensive quantitative connections between CCA loadings, reactivity ratios, polymerization mechanisms, and deconstruction reactions on the deconstruction efficiency of copolymers containing CCAs have not been established. Here, we broadly define these relationships using stochastic simulations characterizing various polymerization mechanisms (e.g., coltrolled/living, free-radical, and reversible ring-opening polymerizations), reactivity ratio pairs (spanning 2 orders of magnitude between 0.01 and 100), CCA loadings (2.5% to 20%), and deconstruction reactions (e.g., comonomer sequence-dependent deconstruction behavior). We show general agreement between simulated and experimentally observed deconstruction fragment sizes from the literature, demonstrating the predictive power of the methods used herein. These results will guide the development of more efficient CCAs and inform the formulation of deconstructable materials.

Biological applications of lipoic acid-based polymers: an old material with new promise

Lipoic acid (LA) is a versatile antioxidant that has been used in the treatment of various oxidation-reduction diseases over the past 70 years. Owing to its large five-membered ring tension, the dynamic disulfide bond of LA is highly active, enabling the formation of poly(lipoic acid) (PLA) via ring-opening polymerization (ROP). Herein, we first summarize disulfide-mediated ROP polymerization strategies, providing basic routes for designing and preparing PLA-based materials. PLA, as a biologically derived, low toxic, and easily modified material, possesses dynamic disulfide bonds and universal non-covalent carboxyl groups. We also shed light on the biomedical applications of PLA-based materials based on their biological and structural features and further divide recent works into six categories: antibacterial, anti-inflammation, anticancer, adhesive, flexible electronics, and 3D-printed tissue scaffolds. Finally, the challenges and future prospects associated with the biomedical applications of PLA are discussed.

Polymeric Nanoparticles for Drug Delivery

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of more sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Furthermore, polymeric nanoparticles have the ability to navigate various biological barriers to precisely target specific sites within the body, encapsulate a diverse range of therapeutic cargo and efficiently release this cargo in response to internal and external stimuli. However, despite these remarkable advantages, the presence of polymeric nanoparticles in wider clinical application is minimal. This review will provide a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles. The biological barriers affecting drug delivery will be outlined first, followed by a comprehensive description of the various nanoparticle designs and preparation methods, beginning with the polymers on which they are based. The review will meticulously explore the current performance of polymeric nanoparticles against a myriad of diseases including cancer, viral and bacterial infections, before finally evaluating the advantages and crucial challenges that will determine their wider clinical potential in the decades to come.

Reversible Thiyl Radical Addition-Fragmentation Chain Transfer Polymerization

Developing reversible-deactivation radical polymerization (RDRP) methods that could directly control the thiyl radical propagation is highly desirable yet remains challenging in modern polymer chemistry. Here, we reported the first reversible thiyl radical addition-fragmentation chain transfer (SRAFT) polymerization strategy, which utilizes allyl sulfides as chain transfer agents for reversibly deactivating the propagating thiyl radicals, thus allowing us to directly control a challenging thiyl radical chain polymerization to afford polymers with well-defined architectures. A linear dependence of molecular weight on conversion, high chain-end fidelity, and efficient chain extension proved good controllability of the polymerization. In addition, density functional theory calculations provided insight into the reversible deactivation ability of allyl sulfides. The SRAFT strategy developed in this work represents a promising platform for discovering new controlled polymerizations based on thiyl radical chemistry.

Bulk Depolymerization of Methacrylate Polymers via Pendent Group Activation

In this study, we present an efficient approach for the depolymerization of poly(methyl methacrylate) (PMMA) copolymers synthesized via conventional radical polymerization. By incorporating low mol % phthalimide ester-containing monomers during the polymerization process, colorless and transparent polymers closely resembling unfunctionalized PMMA are obtained, which can achieve >95% reversion to methyl methacrylate (MMA). Notably, our catalyst-free bulk depolymerization method exhibits exceptional efficiency, even for high-molecular-weight polymers, including ultrahigh-molecular-weight (106-107 g/mol) PMMA, where near-quantitative depolymerization is achieved. Moreover, this approach yields polymer byproducts of significantly lower molecular weight, distinguishing it from bulk depolymerization methods initiated from chain ends. Furthermore, we extend our investigation to polymethacrylate networks, demonstrating high extents of depolymerization. This innovative depolymerization strategy offers promising opportunities for the development of sustainable polymethacrylate materials, holding great potential for various applications in polymer science.

Quantitative, Regiospecific, and Stereoselective Radical Ring-Opening Polymerization of Monosaccharide Cyclic Ketene Acetals

Cyclic ketene acetals (CKAs) are among the most well-studied monomers for radical ring-opening polymerization (rROP). However, ring-retaining side reactions and low reactivities in homopolymerization and copolymerization remain significant challenges for the existing CKAs. Here, we report that a class of monosaccharide CKAs can be facilely prepared from a short and scalable synthetic route and can undergo quantitative, regiospecific, and stereoselective rROP. NMR analyses and degradation experiments revealed a reaction mechanism involving a propagating radical at the C2 position of pyranose with different monosaccharides exhibiting distinct stereoselectivity in the radical addition of the monomer. Furthermore, the addition of maleimide was found to improve the incorporation efficiency of monosaccharide CKA in the copolymerization with vinyl monomers and produced unique degradable terpolymers with carbohydrate motifs in the polymer backbone.

1,1'- Thiocarbonyldiimidazole Radical Copolymerization for the Preparation of Degradable Vinyl Polymers

1,1'-Thiocarbonyldiimidazole (TCDI) readily undergoes radical copolymerization with tert-butyl acrylate (tBA), N,N-dimethylacrylamide, and styrene. 1H NMR monitoring of the comonomer reactivity revealed a notable compatibility between TCDI and comonomers, resulting in similar consumption rates when TCDI was introduced at a 10% feed ratio. Furthermore, trithiocarbonate-mediated RAFT copolymerization of TCDI with tBA gave polymers that exhibited a linear increase of molar mass (Mnth = 2-10 kg mol-1) with conversion with relatively low dispersities (1.2-1.4). Importantly, this process enabled a successful chain extension of the produced P(TCDI-co-tBA) copolymer with styrene to form a diblock copolymer. The copolymers generated through this method contain TCDI-derived diimidazolyl thioether moieties, as established through 1H NMR spectroscopy. Additionally, degradation experiments using isopropylamine, benzoyl peroxide, sodium methoxide, and bleach have provided further confirmation of the presence of degradable TCDI moieties in the vinyl copolymer backbone.