Specific Selectivity of Enzyme-Model Catalyst for a Direct Synthesis of Poly(ethynyl-substituted arylene oxide) via Oxidative Polymerization

Abstract

Oxidative polymerization of 2-(3-ethynylphenyl)phenol (EPP) is performed using an enzyme-model Cu catalyst with a triazacyclononane, and then, a CO coupling polymer is obtained while completely inhibiting homo-coupling of the ethynyl group, which is called Glaser coupling. The produced polymer exhibits highly thermal properties and good solvent resistance through thermal crosslinking of the ethynyl group. In contrast, the oxidation of EPP using a conventional Cu catalyst with an ethylenediamine gives a diacetylene compound, and in the polymerization of 2-ethynylphenol, both catalysts afford polymers with diacetylene structures. The reason for the exclusive CO coupling of the enzyme-model catalyst in the polymerization of EPP is examined using DFT calculations, and as a result, the prohibition of the Glaser coupling would be due to no deprotonation of the ethynyl species to form the acetylide complex. The present polymer resulting from EPP is expected to be a fluorine-free insulating material in high-speed wireless communication systems.