Enzyme-inspired catalysts with high activity and selectivity for oxidative polymerization of 2-phenylphenol

Abstract

Enzyme-inspired copper catalysts having 1,4,7-triazacyclonones substituted at the nitrogen atoms with ^tBu group(s) have been developed for the regioselective oxidative polymerization of 2-phenylphenol. These in situ prepared catalysts remarkably accelerated the polymerization to produce regioregular poly(2-phenylphenylene oxide). The polymer obtained by using the catalyst with one or two ^tBu group(s) exhibited a higher number-averaged molecular weight and a narrower molecular distribution than the polymer synthesized by a previous enzyme-model catalyst lacking ^tBu groups, although a certain amount of free radical coupling occurred in the catalysis with three ^tBu groups. The enzyme-inspired catalysis would proceed through an end-on peroxide complex different from a side-on peroxide complex formed in the enzyme-model catalysis, achieving both the short reaction time and high molecular weight. Thus, a freestanding film was formed by solvent-casting the present polymer, which was reported to show an ultra-low dielectric constant and high thermal stability, and therefore, it could be promising as an insulating polymer in the upcoming sixth-generation technology.