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1. Chemically Recyclable Analogs of Styrene–Butadiene Copolymers Enabling Perfectly Linear Ethylene–Styrene Materials with Random Phenyl Distribution

   https://doi.org/10.1021/acs.macromol.6c01122  

   Satheeshkumar, Chinnadurai; Kennemur, Justin G (June 2026, Macromolecules)

   Copolymerization of cyclopentene (CP) and 4-phenylcyclopentene (4PCP) at a full range of comonomer feed ratios are reported using Ru-based ring-opening metathesis polymerization (ROMP) yielding homogenous copolymers analogous to poly(styrene-ran-1,4-butadiene), and poly(ethylene-ran-styrene) copolymers following hydrogenation under mild conditions. In all cases, total monomer conversions of 86–92% yielded copolymers with compositions within 4% of monomer feeds. Analysis of equilibrium copolymerization thermodynamics, rarely performed on two cycloolefin monomers with low ring strain energies, provides rational design strategies for negotiating two monomers with different equilibrium monomer concentrations. Inverse-gated decoupled 13C NMR analysis of dyad sequences on the resulting copolymer microstructures concludes a near-random distribution of comonomer units. The copolymers produced from ROMP have number average molar masses up to 60 kg mol-1, moderate dispersities (1.5 ± 0.1), and high trans olefin content (86 ± 2%) while glass transitions temperatures follow the Fox equation and span the full range between homopolymer extremities of PCP (–96 °C) and P4PCP (17 °C). Unlike most pre-vulcanized elastomers, these materials undergo facile chemical recycling to monomer, producing complete ring closing metathesis depolymerization (RCMD) of the polymer back to the CP comonomers. Quantitative olefin hydrogenation produced perfectly linear polyethylene with 4–16% of the backbone carbons containing a phenyl pendant, analogous to ES copolymers with up to 71.5% w/w styrene units but with random distribution of the aromatic pendants. Thermal properties of these materials are discussed, which span from semi-crystalline to amorphous, and with Tg values notably less than the reported ES copolymer analogs at similar composition. 

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2. Biobased Copolymers via Cationic Ring-Opening Copolymerization of Levoglucosan Derivatives and ε-Caprolactone

   https://doi.org/10.1021/acsmacrolett.3c00251  

   Porwal, Mayuri K.; Ellison, Christopher J.; Reineke, Theresa M. (July 2023, ACS Macro Letters)

   Simultaneous ring-opening copolymerization is a powerful strategy for the synthesis of highly functional copolymers from different types of cyclic monomers. Although copolymers are essential to the plastics industry, environmental concerns associated with current fossil-fuel-based synthetic polymers have led to an increasing interest in the use of renewable feedstock for polymer synthesis. Herein, we report a scalable synthetic platform to afford unique polysaccharides with different pendant functional groups from biomass-derived levoglucosan and ε-caprolactone via cationic ring-opening copolymerization (cROCOP). Biocompatible and recyclable bismuth triflate was identified as the optimal catalyst for cROCOP of levoglucosan. Copolymers from tribenzyl levoglucosan and ε-caprolactone, as well as from tribenzyl and triallyl levoglucosan, were successfully synthesized. The tribenzyl levoglucosan monomer composition ranged from 16% to 64% in the copolymers with ε-caprolactone and 22% to 79% in the copolymers with triallyl levoglucosan. The allylic levoglucosan copolymer can be utilized as a renewably derived scaffold to modify copolymer properties and create other polymer architectures via postpolymerization modification. Monomer reactivity ratios were determined to investigate the copolymer microstructure, indicating that levoglucosan-based copolymers have a gradient architecture. Additionally, we demonstrated that the copolymer glass transition temperature (Tg, ranging from −44.3 to 33.8 °C), thermal stability, and crystallization behavior could be tuned based on the copolymer composition. Overall, this work underscores the utility of levoglucosan as a bioderived feedstock for the development of functional sugar-based copolymers with applications ranging from sustainable materials to biomaterials. 

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3. Modular Approach to Bio-Based Poly(enol ether)s with Tunable Thermal Properties and Degradability

   https://doi.org/10.1021/acsapm.3c03196  

   Ibrahim, Tarek; Sun, Hao (February 2024, ACS Applied Polymer Materials)

   Biomass-derived polymer materials are emerging as sustainable and low-carbon footprint alternatives to the current petroleum-based commodity plastics. In the past decade, the ring-opening metathesis polymerization (ROMP) technique has been widely used for the polymerization of cyclic olefin monomers derived from biorenewable resources, giving rise to a diverse set of biobased polymer materials. However, most synthetic biobased polymers made by ROMP are nondegradable because of their all-carbon backbones. Herein, we present a modular synthetic strategy to acid-degradable poly(enol ether)s via ring-opening metathesis copolymerization of biorenewable oxanorbornenes and 3,4-dihydropyran (DHP). 1H NMR analysis reveals that the percentage of DHP units in the resulting copolymers gradually increases as the feed ratio of DHP to oxanorbornene increases. The composition of the copolymers plays a pivotal role in governing their thermal properties. Thermogravimetric analysis shows that an increasing percentage of DHP results in a decrease in the decomposition temperatures, suggesting that the incorporation of enol ether groups in the polymer backbone reduces the thermal stability of the copolymers. Moreover, a wide range of glass transition temperatures (16–165 °C) can be achieved by tuning the copolymer composition and the oxanorbornene structure. Critically, all of the poly(enol ether)s developed in this study are degradable under mildly acidic conditions. A higher incorporation of DHP in the copolymer leads to enhanced degradability, as evidenced by smaller final degradation products. Altogether, this study provides a facile approach for synthesizing biorenewable and degradable polymer materials with highly tunable thermal properties desired for their potential industrial applications. 

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4. Oxygen‐Tolerant, Red Light‐Driven Controlled Synthesis of Easily Degradable and High Molecular Weight α ‐Lipoic Acid‐Vinyl Copolymers

   https://doi.org/10.1002/anie.202516164  

   Levkovsky, Ivan O; Trachsel, Lucca; Murata, Hironobu; Matyjaszewski, Krzysztof (October 2025, Angewandte Chemie International Edition)

   Abstract α‐Lipoic acid (LA) has recently emerged as an attractive, inexpensive monomer for synthesizing degradable polymers via ring‐opening of its 1,2‐dithiolane, introducing easily cleavable disulfide linkages into polymer backbones. Reversible addition–fragmentation chain transfer (RAFT) copolymerization with vinyl monomers enables access to degradable poly(disulfide)s with controlled molecular weights. However, conventional thermal RAFT methods suffer from oxygen sensitivity, limited LA incorporation (<40 mol%), and modest degrees of polymerization (DP < 300). Here, we report an oxygen‐tolerant, red‐light‐driven RAFT approach using methylene blue (MB⁺) as a photosensitizer, and triethanolamine (TEOA) as a sacrificial electron donor. This photoRAFT strategy affords well‐defined LA–vinyl copolymers with DPs exceeding 6000, relatively low dispersities (Đ= 1.1–1.6), and LA incorporations up to 68 mol%. The method is compatible with a broad range of functional comonomers, including hydrophilic, charged, and zwitterionic acrylates and acrylamides, yielding water‐soluble degradable polymers. The resulting copolymers are readily degradable by disulfide‐reducing agents, UV light, and ambient sunlight. Overall, this mild and efficient platform overcomes the limitations of thermal RAFT, providing improved access to functional, high‐molecular‐weight degradable LA copolymers, suggesting potential applications as biocompatible plastics and biomedical materials. 

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5. Photoinduced SET to access olefin-acrylate copolymers

   https://doi.org/10.1039/d1py01643a  

   Garrison, John B.; Hughes, Rhys W.; Young, James B.; Sumerlin, Brent S. (February 2022, Polymer Chemistry)

   The advantageous material properties that arise from combining non-polar olefin monomers with activated vinyl monomers have led to considerable progress in the development of viable copolymerization strategies. However, unfavorable reactivity ratios during radical copolymerization of the two result in low levels of olefin incorporation, and an abundance of deleterious side reactions arise when attempting to incorporate many polar vinyl monomers via the coordination–insertion pathway typically applied to olefins. We reasoned that design of an activated monomer that is not only well-suited for radical copolymerization with polar vinyl monomers ( e.g. , acrylates) but is also capable of undergoing post-polymerization modification to unveil an olefin repeat unit would allow for the preparation of statistical olefin-acrylate copolymers. Herein, we report monomers fitting these criteria and introduce a post-polymerization modification strategy based on single-electron transfer (SET)-induced decarboxylative radical generation directly on the polymer backbone. Specifically, SET from an organic photocatalyst (eosin Y) to a polymer containing redox-active phthalimide ester units under green light leads to the generation of reactive carbon-centered radicals on the polymer backbone. We utilized this approach to generate statistical olefin-acrylate copolymers by performing the decarboxylation in the presence of a hydrogen atom donor such that the backbone radical is capped by a hydrogen atom to yield an ethylene or propylene repeat unit. This method allows for the preparation of copolymers with previously inaccessible comonomer distributions and demonstrates the promise of applying SET-based transformations to address long-standing challenges in polymer chemistry. 

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