Bench‐stable potassium complexes for living and isoselective <scp>ring‐opening</scp> polymerization of <scp>rac‐lactide</scp>

Abstract

Abstract To develop bench‐stable and nontoxic catalysts for the ring‐opening polymerization (ROP) of lactides is of importance with the aim of reducing costs in industrial production. Although, recently, some potassium complexes have been reported for the living polymerization of rac‐lactide (rac‐LA), the moisture sensitivities of these complexes prevent their further applications in the mild polymerization condition. In this work, three bench‐stable potassium phenolates as isoselective catalysts for the ROP of rac‐LA were reported, and the moisture stability of these complexes does not inhibit their high activity under mild conditions even in the presence of trace water (2.0 equivalent relative to the catalysts) or unpurified solvents. The controllable polymerization reactions can afford polylactides with desirable molecular weights, which can be high up to M n = 80.0 kg/mol at an anhydrous condition and M n = 54.3 kg/mol in presence of trace water. A best isoselectivity of P m = 0.83 also can be achieved in this system at −70°C.