Chain Shuttling Enantioselective Polymerization: An Effective Strategy for Synthesizing Stereoblock Polythioethers.

Herein, we propose to synthesize stereoblock polythioethers through the chain shuttling enantioselective ring-opening polymerization (ROP) of thiiranes. The use of diastereoisomeric dinuclear Cr complexes with optimized steric hindrance allowed the production of polythioethers with both a head-to-tail content and isotacticity of >99%. In particular, the introduction of dithiols enabled the synthesis of stereoblock polythioethers via a chain shuttling process, thus producing sulfhydryl-telechelic polythioethers with tunable thermal properties. Experimental results and density functional theory calculations indicate that the configuration of the chiral axle of the dinuclear Cr complex determines the enantioselectivity of the asymmetric ROP of thiiranes.