Solid-state photopolymerization of symmetrical and unsymmetrical methoxy substituted diphenylbutadiynes

Abstract

In order to obtain the polydiacetylenes having $\pi$-conjugation between polymer backbone and side chains, symmetrical and unsymmetrical diphenylbutadiyne derivatives with methoxy substituents have been synthesized. Among them, bis(m-methoxypheny) butadiyne, (m,m``)-MPB ($\underline{4}$b), was found to be topochemically polymerized into the polymer single crystals. UV-spectra analysis revealed that the $\pi$-conjugation of this polymer is extended to give a small band gap (the energy difference between HOMO and LUMO). Large third order nonlinear optical properties are expected for (m,m``)-MPB because of its small band gap.