Prediction of microstructure in liquid-crystalline polymers

Abstract

This paper focuses on the importance of distinctly different principal elastic constants in determining the microstructure of main-chain thermotropic liquid-crystalline polymers. A brief survey of microstructures seen in these materials is followed by an outline of established methods of calculating vector fields around defects of predefined topology. The strategy for modelling liquid-crystalline polymers depends on modelling at a molecular level to obtain estimates of the values of the splay, twist and bend constants (the splay is invariably the greatest for main-chain polymers). These parameters then form the input to a lattice model of the microstructure. New developments of the central algorithm of this model enable the splay and bend components to be successfully partitioned in three dimensions, and splay–splay compensated structures to be handled properly. Modelling using the new algorithm for the case where the splay constant is dominant leads to the generation of structures in which twist escaped +1 line singularities are a predominant feature, simulating the experimental surfaces.