MESOSCOPIC DOMAIN THEORY FOR TEXTURED LIQUID-CRYSTALLINE POLYMERS

Here we present a mesoscopic theory of the low-flow-rate rheological properties of textured or polydomain samples of liquid crystalline polymers. In this theory, the Leslie-Ericksen equations are assumed to apply to each domain; these equations are averaged over a spatial region, large compared to a single domain, yet small compared to bulk dimensions. Along with these averaged equations, phenomenological expressions are postulated that allow us to obtain a relatively simple set of coupled equations for the domain size and the mesoscopic orientation and stress tensors. The values of the Leslie-Ericksen viscosities that appear in the equations are obtained from the Doi theory for nematic polymers. We apply the theory to several shear flows, namely recoverable shear after cessation of steady shearing, and step reversal and step increase of shear rate. In each case promising agreement is found between the predictions of the mesoscopic theory and measurements on lyotropic liquid crystalline polymers.