Mixtures of rigid and flexible nematogenic polymers

Abstract

We consider three systems containing rigid and/or flexible main-chain nematogenic polymers: mixtures of a rigid and a flexible polymer, mixtures of two different rigid polymers, and a system of diblocks of rigid and flexible pieces. The flexible components are modeled as chains with freely rotating bonds, while the rigid components are modeled as rods of negligible thickness. The Landau–de Gennes expansion of the free energy is derived, and the form of the phase diagrams is examined. Conditions for the existence of generic diagrams is given in terms of the Flory–Huggins and Maier–Saupe interaction parameters. The location of the azeotrope in the rigid–rigid mixture is calculated analytically. The nematic–isotropic phase transition in the rigid–flexible diblock (in general, n-block) copolymer system is also studied. In particular, the change in the transition temperature with the number of monomers in a rigid block is determined.