Session XC12 - Liquid Crystals.
ORAL session, Friday morning, March 26
Room 268W, GWCC
We construct a liquid-state, integral equation theory describing a liquid crystalline transition of a dense liquid of fully flexible Gaussian polymer chains. The polymers interact only through athermal, repulsive hard-core forces. We demonstrate a novel lyotropic transition from an isotropic to coexisting nematic and discotic phases in the Onsager-like limit of small physical chain thickness compared to the chain statistical segment length. The transition is second order in this limit, but becomes first-order for finite hard-core chain thickness. The structural correlations are anisotropic in the ordered phase. Also, density fluctuations are correlated in an anisotropic sense, indicating that the underlying semi-dilute mesh is anisotropic as well. This structural anisotropy has a natural interpretation in terms of lessened monomer-monomer collisions along the director axis, and thus is a starting point for understanding the enhanced flow properties of liquid crystalline polymers. We demonstrate that our formalism reproduces the qualitative features of Onsager's theory of the isotropic-nematic transition of hard, thin rods.