Chemical Recycling of Step-Growth Polymers Guided by Le Chatelier's Principle

Although step-growth polymers (SGPs) play a fundamental role in the plastics economy, contributing significantly to various facets of our daily life, their end-of-life management remains inadequately addressed. Chemical recycling of SGP wastes, involving depolymerization followed by repolymerization, emerges as a promising solution toward achieving a circular plastics economy. The depolymerization of SGPs is usually in dynamic equilibrium with their polymerization reactions, thus falling under a system amenable to Le Chatelier's principle. This perspective endeavors to elucidate the interplay between Le Chatelier's principle and the chemical recycling of SGPs with a particular emphasis on the guidance provided by the principle in the latter process. To this end, we have selected five conventional SGPs, namely, poly(ethylene terephthalate), polyamides, polycarbonates, polyurethanes, and polyureas, as representatives to elucidate how alterations in temperature, pressure, concentrations of products or reactants, and catalysts influence the depolymerization process of SGPs. Additionally, the perspective proposes several potential strategies for achieving the chemical recycling of SGPs by applying Le Chatelier's principle.