Ring-opening terpolymerisation of phthalic thioanhydride with carbon dioxide and epoxides†

In seeking to expand the portfolio of accessible polymer structures from CO₂ waste, we report the ring-opening terpolymerisation (ROTERP) of phthalic thioanhydride with CO₂ and epoxides, forming statistical poly(ester-thioester-carbonates) by employing heterobimetallic catalysts. Both metal choice and ligand chemistry modulate the amount of CO₂ incorporated into the polymer microstructure. Terpolymerisation occurs when maintaining polymerisation rates of the faster parent ring-opening copolymerisation and this finding led us to develop the formation of CO₂-derived terpolymers with butylene oxide at low CO₂ pressure under bicomponent catalysis. Tetrapolymerisation with added phthalic anhydride leads to the preferential polymerisation of phthalic anhydride before the polymerisation of sulfur derivatives with CO₂ and epoxides. Finally, we show that the presence of sulfur-containing thioester links leads to polymers with degradability benefits compared to those from all-oxygen derivatives.