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

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.