Thiol-Yne click polymerization: Regio- and stereoselective synthesis of sulfur-rich acetylenic polymers with controllable chain conformations and tunable optical properties

The atom-economical alkyne polyhydrothiolations of aromatic diynes (1) and dithiol (2) catalyzed by rhodium complexes proceed smoothly under mild conditions at room temperature in a regioselective manner, producing sole anti-Markovnikov products of poly(vinylene sulfide)s (3) with high molecular weights (M_w up to 31500) and stereoregularities (E content up to 100%) in high yields (up to 95.2%). The stereostructures of the polymers are readily tuned by engineering control on the sequential addition of monomers during the polymerization process and postmanipulation by light irradiation. All the poly(vinylene sulfide)s are soluble in common organic solvents and exhibit good film-forming ability and high optical transparency. The functional pendants in 1 have endowed 3 with novel properties such as aggregation-enhanced emission characteristics, optical limiting to harsh laser pulses, and ceramization capability to semiconducting nanoparticles. The polymers are thermal and UV curable, enabling the fabrication of fluorescent photopatterns. Their thin films show high refractive indices (n_D = 1.75-1.70) and low optical dispersions (down to 0.006) at telecom important wavelengths. Their refractive indices vary with their stereostructures and can be modulated by UV irradiation.