Mechanochemical Degradation of Poly(vinyl chloride) into Nontoxic Water-Soluble Products via Sequential Dechlorination, Heterolytic Oxirane Ring-Opening, and Hydrolysis.

Abstract

As one of the most widely used commodity plastics, poly(vinyl chloride) (PVC) is extensively used worldwide, yet is difficult to recycle and is often discarded immediately after use. Its end-of-life treatment often generates toxic hydrogen chloride and dioxins that pose a critical threat to ecosystems. To address this challenge, the mechanochemical degradation of PVC into water-soluble biocompatible products is presented herein. Oxirane mechanophores are strategically introduced into the polymeric backbone via sequential dechlorination followed by epoxidation. The oxirane mechanophore in the polymer backbone undergoes a force-induced heterolytic ring-opening to carbonyl ylide intermediates, which eventually generates acetals during the course of the reaction. The subsequent hydrolysis of the backbone acetals affords the scission of the polymeric chain into water-soluble low-molecular-weight fragments. Combined with its low cytotoxicity and phytotoxicity, this solvent-free mechanochemical degradation process offers a green alternative for the degradation of PVC.