Design for Recycling: Polyester- and Polycarbonate-Based A–B–A Block Copolymers and Their Recyclability Back to Monomers

Abstract

Chemical recycling to monomers (CRMs) of A–B–A block copolymers is governed by the chemical structure and thereby the thermodynamic behavior of different block constituents. Here, we show how a thermodynamic toolkit based on a cyclic monomer structure and solvent properties can be utilized in the design of recyclable A–B–A block copolymers with varying material properties. By combining four cyclic monomers lactide, ε-decalactone, 2,2-diethyltrimethylene carbonate, and trimethylene carbonate, three different block copolymers were created, suitable for different CRM scenarios. The chemical structure of the soft midblock (ε-decalactone or trimethylene carbonate) appeared to have a critical impact both on the ring-closing depolymerization behavior and mechanical properties, where changing from a polyester to a polycarbonate soft block increased Young’s modulus from 14 to 200 MPa. Hence, this work demonstrates the complexity as well as the opportunities in the design of macromolecular structures for a circular economy.