Photocurable selenophene/maleimide-based high-refractive-index copolymers obtained via radical copolymerization

Abstract

Selenophene-containing copolymers with either alternating or random sequences and high refractive indices were synthesized via conventional free-radical copolymerization of 2-vinylselenophene (2VS). Copolymers with a moderate alternating tendency were obtained via radical copolymerization of electron-donating 2VS and electron-accepting maleimide derivatives, such as N-methyl maleimide (MMI), N-phenyl maleimide (PMI), and N-vinyl maleimide (VMI). Copolymerization of 2VS with glycidyl methacrylate (GMA) also afforded copolymers containing selenophene and reactive epoxy units in the side chains. The selenophene-containing poly(2VS) showed a high refractive index (1.6420 @ 589 nm) and a reasonable Abbe number (30.7). High refractive indices of 1.6138–1.5959 with corresponding Abbe numbers of ~30 were similarly achieved for the selenophene/maleimide copolymers. The introduction of the maleimide moiety into the polymer side chain improved its thermal stability (Td5 > 320 °C) and enhanced the glass transition temperature (Tg = 158–160 °C). Selenophene-containing copolymers with pendant N-vinyl units were obtained via copolymerization of 2VS and VMI, which was successfully employed as a precursor for obtaining a photoinduced crosslinked film via a thiol-ene reaction with 1,6-hexanedithiol in the presence of a photo-radical initiator under ultraviolet irradiation. Thus, for the first time, photocurable and high-refractive-index selenophene-based copolymers were developed through the combination of a selenophene-containing vinyl monomer and a maleimide derivative with a pendant N-vinyl group.