Polymerization of 1,4-bis(tetrahydrothiopheniomethyl)-2-cyano-5-methoxybenzene dibromide: synthesis of electronically ‘push-pull’ substituted poly( p-phenylene vinylene)s

Abstract

The base-induced polymerization of 1,4-bis(tetrahydrothiopheniomethyl)-2-cyano-5-methoxybenzene dibromide in aqueous acetonitrile yields a soluble polyelectrolyte which may be thermally eliminated to give the electronically ‘push-pull’ substituted poly(2-cyano-5-methoxy-1,4-phenylene vinylene). Ultraviolet-visible and infra-red spectral studies showed production of the conjugated polymer, with a band gap of ca. 2.6–3.0eV (410–480 nm) that varied somewhat as a function of elimination conditions. Elemental analysis indicates some retention of tetrahydrothiophenium side groups in the polyelectrolyte polymer, despite the use of a variety of elimination conditions. The retention of side chains in this synthesis is possibly due to a significant degree of irregularity in the positions of the cyano and methoxy substitutents in the eliminated polymer, resulting from non-regioselectivity in this polymerization. This reaction demonstrates the potential in the Wessling process for polymerization of p-xylylenes that have electronically very asymmetric (‘push-pull’) substitution patterns.