Green Light-Driven, Oxygen-Tolerant Photoinduced Electron/Energy Transfer Reversible Addition-Fragmentation Chain Transfer Polymerization of Lipoic Acid with Maleimide and Vinyl Ethers

We report a green-light-driven, oxygen-tolerant photoinduced electron/energy transfer-reversible additon-fragmentation chain transfer (PET-RAFT) terpolymerization of a multicomponent system comprising lipoic acid (LA), a maleimide (MI), and a vinyl ether (VE). By introducing LA into a donor-acceptor monomer pair, this strategy extends the controlled radical polymerization of LA beyond conventional acrylate/acrylamide systems, yielding degradable vinyl polymers with tunable molecular weights (6.2−61.5 kg mol−1) and relatively low dispersities (Đ = 1.2−1.5). The resulting materials show pathway-dependent degradability: TCEP selectively reduces disulfide bonds to thiols, giving a moderate reduction in molecular weight (61.5 → 15.7 kg mol−1), whereas thiolate-mediated exchange at both the disulfide and LA-MI succinimidyl thioether (SITE) bonds causes extensive backbone cleavage (61.5 → 2.1 kg mol−1). Retention of the trithiocarbonate chain end enabled the synthesis of amphiphilic diblock copolymers that self-assemble into micelles and release their cargo under reducing conditions. This work establishes a robust, mild, oxygen-tolerant platform for incorporating disulfide and SITE bonds into previously inaccessible classes of vinyl polymers, expanding the scope of functional LA-containing materials for sustainable plastics and stimuli-responsive degradable materials.