Topochemical Ring-Opening Polymerization of an Oxathianethione

Single crystals of an enantiopure oxathianethione (OTT) were found to spontaneously convert to the corresponding polymer (POTT) through topochemical ring-opening polymerization (topoROP). The polymerization proceeds quantitatively and stereospecifically to give crystalline POTT with high molecular weights. The resulting POTT crystals were suitable for structure determination through X-ray crystallography to reveal polymers with right-handed helices with an antiparallel arrangement of polymer chains. Control studies support a concerted nucleophilic substitution mechanism that proceeds in the absence of radical intermediates, and the polymerization is suppressed when the monomer is randomly organized in an amorphous glass. Overall, this represents a distinct class of topochemical polymerization that opens new opportunities to prepare highly crystalline sulfur-containing materials.