Nematic Phase Transition in Systems of Polymer Chains with Mesogenic Groups

Abstract

Nematic phase transition in melts of mesogenic macromolecules is studied. Each polymer chain is regarded as a sequence of rigid and flexible segments. Mean field approximation is used to calculate free energy of the system. Equilibrium temperature dependences of order parameters are obtained both for rigid and flexible fraction, and phase transition temperature is calculated. It is examined how lengths of different chain segments and values of anisotropic interaction between them can influence various properties of phase transition in the system. In a set of cases more often realized in experiments (when flexible segments are shorter or at least comparable with rigid ones) ordering of flexible component proves to be extremely weak in the vicinity of phase transition point. But there is a range of values of flexible spacer relative length and of anisotropic interaction between different segments when flexible fraction turns out to be even more ordered than rigid one in the vicinity of phase transition point.

Key Words:

• nematic transition
• polymer melts