Electrorheological determination of the Leslie viscosity coefficient (α₂) of a main-chain liquid crystal polymer in a nematic solvent

Abstract

Analysis of the electrorheological response of thermotropic solutions of a main-chain liquid crystal polymer (MCLCP) in a low molar mass nematic solvent is performed at a fixed shear rate as a function of the applied field strength. The Leslie viscosity coefficient α₂ can be obtained by least squares fits to an equation describing the balance between the viscous and electric torques, formulated via the two dimensional Leslie-Ericksen-Parodi theory. We find that the increment Δα₂ on dissolving the MCLCP increases linearly with molecular weight, consistent with earlier light scattering measurements of the increment in the twist viscosity, Δγ₁, and also with previous electrorheological measurements of the increment in the Miesowicz viscosity Δη_c.