POLYDISPERSE POLYMER LIQUID-CRYSTALS NEAR THE ANISOTROPIC-ISOTROPIC TRANSITION

Polydisperse systems of polymer liquid crystal (PLC) macromolecules co nsisting of LC and flexible sequences are considered, particularly at the phase transition LC-i from an anisotropic to the isotropic phase. The Flory and Matheson lattice model is used for formulation of the pa rtition function; the orientation distribution function for LC orienti ng potential interactions introduced by Flory and Ronca is included. U sing a Landau approach to calculating the Helmholtz function of the sy stem as a function of the orientation parameter s, we obtain the formu lae for parameters of the model in the vicinity of the LC-i transition . The critical values at the transition of s, of the strength of orien ting interactions, the system temperature, and the anisotropy of LC se quences are calculated and discussed as functions of the polydispersit y parameter d. Regions of d are found where polydispersity has a weak influence on the LC-i equilibrium parameters. There is also a region o f d values in which the influence of polydispersity is quite pronounce d.