Lattice model studies of the effect of chain flexibility on the nematic–isotropic transition. I. Rigid cores having completely flexible tails

Abstract

A steric, mean field, three-dimensional, simple cubic lattice model using DiMarzio lattice statistics for molecules composed of rigid cores and completely flexible pendant tails is presented. The calculated trends and absolute values of the following properties at the nematic–isotropic transition for cores of length-to-breadth ratios of 5 and 10 with tails of varying length are discussed and compared with relevant experimental data: temperature, core order parameter, intermolecular tail order parameter, densities, relative density change, and entropy change. The results indicate that although completely flexible tails in this model are too flexible compared with hydrocarbon tails in real liquid crystals, tail flexibility of some degree should be important in the nematic–isotropic transition.