Chemoselective ring-opening copolymerization of five-membered cyclic carbonates and carbonyl sulfide toward poly(thioether)s

Abstract

Five-membered cyclic carbonates (5-CCs) have the advantages of wide availability, low toxicity, and low volatility, but extremely low ring strain makes them thermodynamically “non-polymerizable” monomers. This work, for the first time, reports the copolymerization of propylene carbonate (PC) with carbonyl sulfide (COS) to prepare poly(thioether)s via a one-pot/one-step protocol. The polymerization involves several successive steps, including in situ generation of propylene oxide (PO) from decarboxylation of PC, coupling of COS/PO to cyclic thiocarbonate (CTC), in situ generation of propylene sulfide (PS) from decarboxylation of CTC, and ring-opening polymerization of PS. The resultant polymers incorporate mostly thioether units (65–100 mol%) and a few thiocarbonate units. The content of the two units is regulated by changing the reaction conditions and commercially available catalysts. We also tune the thermal properties and degradation potential of the polymers by introducing different contents of thioether/thiocarbonate units. This polymerization method provides a new approach for the application of 5-CCs and the preparation of poly(thioether)s.