Geminal Dimethyl Substitution Enabled Controlled Ring-Opening Polymerization and Selective Depolymerization of Penicillamine-Derived β-Thiolactones

To access infinitely recyclable plastics, one key is to design thermodynamically neutral systems based on dynamic bonds for easy manipulation of the polymerization and the reverse depolymerization under low energy cost. Here, we present the controlled ring-opening polymerization of various penicillamine-derived β-thiolactones and the highly specific depolymerization of the resultant polythioesters (PN^R-PenTE) for complete monomer recycling. The gem-dimethyl group confers better ROP control by reducing the activity of the chain-end thiolate groups and stabilizing the thioester linkages in the polymer backbone. High molar mass and narrow dispersity PN^R-PenTE are conveniently accessible at room temperature bearing well-defined end groups and tunable side chains. PN^R-PenTE can be tailored with water solubility, and/or be easily fabricated into persistent films or fibers with interesting thermal and mechanical properties. Most importantly, PN^R-PenTE can be recycled to pristine enantiopure β-thiolactones at >95% conversion in a well-controlled unzipping fashion within min to hours at room temperature. Overall, this work may streamline the rapid development of a wide range of polythioesters with immense application potential as self-immolative building blocks, high value biomaterials, and sacrificial domain for nanolithography.