Dual-Degradable and Reprocessable Hyperbranched Polymers from Chain Transfer Agent-Lipoic Acid Conjugate

Hyperbranched polymers (HBPs) offer exceptional functionality, high solubility, and processability due to their dense branching and terminal group density, yet achieving degradable and recyclable HBPs remains a challenge. In this study, we introduce a novel lipoic acid (LA)-based chain transfer agent (CTA-LA) for reversible addition–fragmentation chain transfer (RAFT) polymerization that acts both as a branching comonomer via radical ring-opening polymerization and as a RAFT agent to enable the controlled synthesis of HBPs. Through thermal and photochemical conditions, we synthesized a library of linear and hyperbranched copolymers with tunable architectures and dual-degradable linkages, disulfides from the dithiolane ring and esters from the CTA-LA conjugation. Structural characterization via NMR, SEC, and DLS confirmed successful polymer formation, branching, and degradation. Systematic variation of CTA-LA feed ratios revealed a trade-off between conversion and branching density, with more compact architectures formed at higher CTA-LA content. We demonstrated polymer degradation under reductive and basic conditions and leveraged the thiol-containing degradation products for thiol–ene cross-linking into reprocessable thermoset networks. Additionally, we employed the HBPs as thermosetting prepolymer resins through a photo-cross-linking process. These results establish, for the first time, LA-based RAFT agents as versatile transmers (chain transfer agent-monomer conjugate) for designing HBPs with degradable, recyclable, and reprocessable properties, enabling circular design and future applications in soft materials, adhesives, and sustainable polymer systems.