Specific interactions in discotic liquid crystals

Abstract

A series of novel mesogens have been prepared by a five-fold Sonogashira reaction of terminal acetylenes with a functionalized pentabromophenol derivative. The corresponding side-chain substituted polymers were prepared by an analogous polymer substitution reaction. The mesogens differ in the nature of the substituents, i.e. CH₂, O, S, SO₂ and CONH groups, linking five hexyl tails to the core. A wide range of mesophases and corresponding transition temperatures have been detected, varying from low melting nematic phases to highly stable columnar phases. The wide spread in phase behaviour is described in terms of specific intermolecular interactions. The addition of planar electron deficient molecules resulted in the formation of charge transfer complexes. The observed stabilisation or destabilisation of the mesophases is explained by considering the complexation strength of the complex as well as steric factors.