ABSTRACT: The completely alternating copolymerization of carbonyl sulfide (COS) and styrene oxide was found to occur under mild reaction conditions (0-30 °C and 1.5 MPa) in the presence of (salen)CrCl/onium salt catalyst systems to afford high molecular weight poly(monothiocarbonates) with narrow molecular weight distributions. Ring-opening of styrene oxide was shown to be 88% selective at the methylene carbon. That is the reaction is driven by steric hindrance, where ring-opening occurs preferentially at the less congested carbon center. Similar results were found upon utilizing the tetramethyltetraazaannulene (tmtaa)CrCl/onium salt catalyst. On the other hand, upon employing a zinc?cobalt double metal cyanide (Zn?Co DMCC) catalyst, where the ligands around the active zinc site are not sterically encumbering, ring-opening of styrene oxide occurs predominantly at the methine carbon site; i.e., the reaction is electronically driven.

Macromolecules 2015, 48, 6057-6062