Electrorheological Behavior of Main-Chain Liquid Crystal Polymers Dissolved in Nematic Solvents

Influence of shear flow on the linear response of a nematic liquid crystal to external electric fields

We have investigated the linear response of shear stress to ac electric fields under shear flow in a nematic liquid crystal. The experimental results were compared with the theoretical results derived from the Ericksen-Leslie theory. Although close agreement was obtained at low shear rates, discrepancies were observed at high shear rates. By introducing a two-mode coupling model the experimental results were well reproduced for the entire range of shear rates, and nonconservative forces were found to play an important role in determining the fluctuation dynamics, which is a characteristic of nonequilibrium steady states.

Conformational transitions of a semiflexible polymer in nematic solvents

Conformations of a single semiflexible polymer chain dissolved in a low-molecular-weight liquid crystalline solvent (nematogen) are examined by using a mean field theory. We take into account a stiffness and partial orientational ordering of the polymer. As a result of an anisotropic coupling between the polymer and nematogen, we predict a discontinuous (or continuous) phase transition from a condensed-rodlike conformation to a swollen one of the polymer chain, depending on the stiffness of the polymer. We also discuss the effects of the nematic interaction between polymer segments.