Mechanochemically Promoted Functionalization of Postconsumer Poly(Methyl Methacrylate) and Poly(α‐Methylstyrene) for Bulk Depolymerization

We describe a methodology of post‐polymerization functionalization to enable subsequent bulk depolymerization to monomer by utilizing mechanochemical macro‐radical generation. By harnessing ultrasonic chain‐scission in the presence of N‐hydroxyphthalimide methacrylate (PhthMA), we successfully chain‐end functionalize polymers to promote subsequent depolymerization in bulk, achieving up to 82 % depolymerization of poly(methyl methacrylate) (PMMA) and poly(α‐methylstyrene) (PAMS) within 30 min. This method of depolymerization yields a high‐purity monomer that can be repolymerized. Moreover, as compared to the most common methods of depolymerization, this work is most efficient with ultra‐high molecular weight (UHMW) polymers, establishing a method with the potential to address highly persistent, non‐degradable all‐carbon backbone plastic materials. Lastly, we demonstrate the expansion of this depolymerization method to commercial cell cast PMMA, achieving high degrees of depolymerization from post‐consumer waste. This work is the first demonstration of applying PhthMA‐promoted depolymerization strategies in homopolymer PMMA and PAMS prepared by conventional polymerization methods. We report a methodology of post‐polymerization functionalization to enable bulk depolymerization by chemically recycling to monomer utilizing mechanochemical macro‐radical generation. When sonicated in the presence of a depolymerizable trigger, postconsumer PMMA and PAMS can achieve up to 82 % depolymerization. High‐purity monomer is collected and used in new materials. This method of functionalization is particularly effective with Mn>1 million kg/mol polymers, offering a sustainable solution for plastic waste management.