Self-switchable Polymerization Catalysis with Monomer Mixtures: Using a Metal-Free Commercial Thiourea Catalyst to Deliver Block Polyesters

Self-switchable polymerization is a versatile and convenient synthetic approach to producing block copolymers that utilizes different monomer mixtures and sequence polymerizations in a single pot. The development of simple and efficient metal-free organocatalysts for self-switchable polymerization is a current hot topic in research. Herein, we present a simple and cost-effective TU/PPNCl {TU: 1,3-bis[3,5-bis(trifluoromethyl)phenyl]thiourea} binary catalytic system that can switch between epoxides, cyclic anhydrides and cyclic esters, resulting in the production of sequence-controlled multiblock polyesters with a diverse range of structures. The successful construction of precise triblock copolymer structures has been confirmed through NMR, in situ IR, and SEC analysis. The experimental results confirmed the successful formation of selectively structured epoxide/anhydride and cyclic ester blocks. Metal-free thiourea catalysts show great potential for synthesizing complex polymers with sequential and structural diversity, offering opportunities for the synthesis of diverse and functional multiblock copolymer materials. An easily accessible and cost-effective catalytic system, TU/PPNCl, was developed to produce sequence-controlled multiblock polyesters by self-switchable polymerization from a monomer mixture of epoxides, anhydrides, and cyclic esters.