Synthesis of poly(thiourethane-alt-thioester) by alternating ring-opening copolymerization of N-thiocarboxyanhydrides and episulfides

Polythiourethanes (PTU) and polythioesters (PTE) derived from renewable sources are emerging sustainable polymers for their excellent degradability and recyclability. However, P(TU-alt-TE) copolymers have been rare and challenging to synthesize. Here, we report the efficient synthesis of novel P(TU-alt-TE) copolymers via the alternating copolymerization of N-thiocarboxyanhydrides (NTA)/episufides (ES) and provide mechanistic insight into the alternating chain propagation process via density functional theory (DFT) calculation. The incorporation of ESs into traditional peptide backbone is capable of adjusting the glass transition temperature below thermal decomposition temperature, which confers better thermal processability by regulating the rigidity of the backbone and the hydrogen bond interaction among the polymer chains. Crosslinked PTUs with tailored properties are accessible by altering the feeding ratio of NTAs and (bifunctional) ESs. Moreover, the thiourethane in the backbone can endow interesting underwater adhesion properties to the materials. Considering the broad scope of NTA and ES monomers, this method is expected to provide a promising and general route to a wide range of P(TU-alt-TE) copolymers with diverse properties.