Structure and thermodynamics of anisotropic polymer fluids

We investigate the structure and thermodynamics of anisotropic polymer flui ds, focusing on the nematic phases of flexible polymers. The chains interac t only through monomer-monomer excluded-volume interactions. As a function of an externally provided alignment along a fixed nematic director, we calc ulate the anisotropic pair correlation function, and demonstrate the existe nce of two density correlation lengths, xi(perpendicular to) and xi(z), con trolling transverse and longitudinal density fluctuations, respectively. We allow the possibility that the chains align either along the director (nem atic conformations), or are anti-aligned in a "discotic-like" configuration . The cohesive contribution to the free energy is established in a high-tem perature approximation, and its sensitivity to the orientation of the chain s is probed. Our approach is not limited to homogeneous liquid crystalline phases, but applies in any circumstance when the orientation of otherwise d isordered polymers is the physically controlling effect, e.g., confinement in thin films or pores, shear-alignment of flexible polymers, or straining a cross-linked rubber network. (C) 2000 American Institute of Physics. [S00 21-9606(00)51410-X].