Micro-segregation, molecular shape and molecular topology – partners for the design of liquid crystalline materials with complex mesophase morphologies

Abstract

This article gives an overview of recent progress in the design of novel materials, capable of forming liquid crystalline phases with non-conventional mesophase morphologies. The materials include dendritic molecules, ternary block-copolymers, rod–coil molecules and linear as well as non-linear polyphilic low molecular weight block molecules incorporating rigid segments with a specific shape. Changing the shape of the rigid segments from rod-like to disc-like or to a bent shape leads to additional possibilities for the directed design of mesophase forming materials. Many of these molecules are able to form quite unusual mesophase morphologies, distinct from the conventional lamellar (smectic) and columnar mesophases of classical rod-like and disc-like liquid crystals; they include mesophases which combine lamellar and columnar organisation, columnar mesophases incorporating three discrete sets of columns, biaxial smectic phases, such as the SmAb-phase (McMillan Phase), polar smectic phases and non-conventional layer structures in which rigid units are aligned parallel to the layers. These novel mesophase morphologies were realised by increasing the number of incompatible units combined in these molecules, by changing the volume fractions of the incompatible segments, by tailoring the shape of rigid segments and by controlling the molecular topology.