Metal-Free Alternating Copolymerization of Nonstrained γ-Selenobutyrolactone with Epoxides for Selenium-Rich Polyesters

The placement of selenium (Se) atoms into polymers to achieve functional materials for diverse applications in adaptive and biomedical materials has attracted broad interest. However, the difficulty in creating well-defined Se-rich polymers is a critical limitation. In this work, we report the successful alternating and regioselective copolymerization of nonstrained gamma-selenobutyrolactone with epoxides. Poly(selenide-alt-ester)s containing selenide and ester groups in each repeating unit are achieved under mild reaction conditions. The process mediated by the phosphazene base (P2)/alcohol at 25 degrees C exhibits high activity and living behavior, as evidenced by narrow molecular weight distributions (1.05-1.29) and switch on-off chain extension experiments. The nucleophilic attack of epoxides by selenol anions is the rate-determining step according to kinetic studies. The resultant Se-containing polyesters possess >99% alternating degree, >99% regioregularity, and programmable hydroxyl terminals. More importantly, these poly(selenide-alt-ester)s exhibit the initial thermal decomposition temperatures of up to 275 degrees C, low glass-transition temperatures of down to -59 degrees C, excellent solvability in common organic solvents, high refractive indexes (1.61-1.62), and good ionic conductivity (when doped with Li salt, 1.09 x 10(-6) S/cm at 30 degrees C, 1.73 x 10(-4) S/cm at 100 degrees C), indicating potential broad application prospects of these Se-rich polyesters.