Synthesis of Degradable Polystyrene and Its Derivative with In-Chain Thioester via Radical and Cationic Copolymerizations with a Seven-Membered Benzene-Fused Thionolactone.

Vinyl polymers are widely used in modern society, but their all-carbon backbones make them highly resistant to degradation. One of the most effective solutions is to copolymerize them with cleavable monomers, resulting in degradable polymers that maintain thermal and mechanical properties similar to those of the original materials. Thionolactones have emerged as promising comonomers; however, only a few thionolactones are currently available for the preparation of degradable vinyl-based copolymers with unique reactivity. In this study, we developed a seven-membered, benzene-fused thionolactone, MBDT, as a comonomer and synthesized degradable polystyrene and its derivatives with thioester groups distributed along the chain through both radical and cationic copolymerizations. These copolymers can be degraded into short-chain fragments, which can then be recovered through oxidative repolymerization. Additionally, leveraging MBDT's high copolymerization reactivity with styrene, we successfully conducted reversible addition-fragmentation chain transfer (RAFT) copolymerization, achieving controlled molecular weights (M n 's) and narrow dispersities (Đ <1.2). Furthermore, we also successfully prepared degradable poly-(p-methoxystyrene) via the cationic copolymerization of MBDT and p-methoxystyrene (MOS).