Dual-Degradable and Reprocessable Hyperbranched Polymers from Chain Transfer Agent-Lipoic Acid Conjugate
Mithun Kumar Debnath, Nehal Nupnar, Yichun Yuan, Ezra Kone, Valentin O. Rodionov, Michael J. A. Hore, Metin Karayilan
Abstract
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 trans fer agent-mono mer conjugate) for designing HBPs with degradable, recyclable, and reprocessable properties, enabling circular design and future applications in soft materials, adhesives, and sustainable polymer systems.