Effect of Alkyl-Chain Length on Liquid-Crystalline Properties in Viologens with an Asymmetric Core

Abstract

Viologens (N,N’-dialkyl-4,4’bipyridinium salts) are functional materials responded to various external stimulus. In this study, extended viologens with an asymmetric rigid moiety (nNNPm) were synthesized by the Menshütkin reaction, Zincke reactions and anion metathesis reactions. Their liquid-crystalline (LC) properties were investigated. When one of the alkyl chains of nNNPm, especially the alkyl chain attached to the pyridine, was short, no LC phase was observed. The TLC-Iso became higher when n was larger than m in nNNPm.