Microwave-Assisted Depolymerization of Polymethacrylates

Abstract

Advancing sustainability in the polymer industry requires efficient, ecofriendly recycling strategies. This study introduces a catalyst-free, microwave-assisted depolymerization method for RAFT-terminated polymethacrylates, utilizing methanol as a dual-functional cosolvent to enhance microwave absorption and provide a benign reaction medium. The effectiveness of this approach was demonstrated primarily with poly(methyl methacrylate) (PMMA), including variations in molecular weight (M_n ≈ 5k, 12k, 17k g/mol) and RAFT end-groups (dithiobenzoate and trithiocarbonate). Applicability was further confirmed with poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(benzyl methacrylate) (PBzMA). Depolymerization efficiency showed strong temperature dependence, with significant monomer recovery observed between 110 and 140 °C, while operating effectively at high repeat unit concentrations (up to 200 mM). This rapid, catalyst-free process, operating efficiently at elevated temperatures like 120 °C, presents a green, scalable, and economically viable recycling solution, aligning with circular economy principles to mitigate polymer waste.