Thermally Stable Polysulfones Obtained by Regiospecific Radical Copolymerization of Various Acyclic and Cyclic 1,3-Diene Monomers with Sulfur Dioxide and Subsequent Hydrogenation

Abstract

We synthesized the thermally stable alternating copolymers from various acyclic and cyclic alkyl-substituted 1,3-diene monomers with sulfur dioxide (SO2) as the starting comonomers by radical copolymerization and subsequent hydrogenation. It was revealed based on the DFT calculation results using model reactions as well as the thermodynamic analysis of polymerization that some propagation steps were reversible and the highly 1,4-regiospecific sequences of the poly(diene sulfone)s (PDSs) were consequently produced via a free radical propagation mechanism. The stereochemical structures of the PDSs obtained from cyclic 1,3-diene monomers, such as 1,3-cyclopentadiene and 1,3-cyclohexadiene, were also estimated based on the DFT calculations. Transparent films with a refractive index of 1.53–1.55 were readily obtained by casting the PDS solutions, being confirmed to be amorphous by wide-angle X-ray diffraction measurements. The decomposition of the PDSs started below 150 °C, but hydrogenation produced thermally...