Geminal Dimethyl Substitution Enables Controlled Polymerization of Penicillamine-Derived β-Thiolactones and Reversed Depolymerization

To access infinitely recyclable plastics, one appealing approach is to design thermodynamically neutral systems based on dynamic covalent bond, the (de)polymerization of which can be easily manipulated with low energy cost. Here, we demonstrate the feasibilit y of this concept via the efficient synthesis of polythioesters PNR-PenTE from penicillamine-derived beta-thiolactones and their convenient depolymerization under mild conditions. The gem-dimethyl group adjusts the thermodynamics of (de)polymerization to near equilibrium, confers better (de)polymerization control by reducing the activity and conformational possibilities of the chain-end thiolate groups, and stabilizes the thioester linkages in the polymer backbone. PNR-PenTE with tailored properties is conveniently accessible by altering the side chains. PNR-PenTE can be recycled to pristine enantiopure beta-thiolactones at >95% conversion from minutes to a few hours at room temperature. This work highlights the power of judicious molecular design and could greatly facilitate the development of a wide range of recyclable polymers with immense application potentials.