Thermal and optical properties, and aggregated structure of poly(substituted methylene)s produced by radical polymerization of fumarates containing fluorine-substituted alkyl ester groups

Abstract

Fluoropolymers have excellent heat, oxidation, and chemical resistances as well as low dielectric constant and dielectric loss, and are often used as highly functional optical polymer materials. In this study, we conducted the radical polymerization and copolymerization of asymmetric dialkyl fumarates, in which a bulky alkyl group is introduced into one ester group and a trifluoroethyl or hexafluoroisopropyl group is into another ester group. We successfully synthesized high-molecular-weight poly(dialkyl fumarate)s (PDRF) with a poly(substituted methylene) structure containing fluorine atoms in the side chain, and evaluated their structure and physical properties. First, the effect of fluorine substitution on the radical polymerization and copolymerization reactivity was examined. We also evaluated the thermal and optical properties of the fluorine-containing PDRFs and clarified the role of the fluorine substitution for increasing the β transition temperatures and reducing the refractive indices. Furthermore, the higher-order structure of the PDRFs in the solid state was analyzed by wide-angle X-ray scattering (WAXS) measurement in order to discuss the aggregation of the rigid PDRF chains and a possibility for the formation of a phase-separated microstructure by the fluorine-containing side chains.