Linear viscoelasticity of nematic liquid crystalline polymers.

A general phenomenological equation is given for the viscoelasticity of nematic fluids in small-amplitude deformations. It is a time integral containing three independent relaxation moduli, which are coefficients of the terms gamma sub (alphabeta), gamma sub (alphamicron) n sub (micron) n sub (beta) + n sub (alpha) n sub (nu) gamma sub (nubeta), and gamma sub (micronnu) n sub (micron) n sub (nu) n sub (alpha) n sub (beta), where gamma sub (alphabeta) is the rate-of-deformation tensor and n sub (alpha) is the director. For small amplitudes, the equation reduces to Ericksen's transversely isotropic fluid. The three moduli are computed for the Doi theory for concentrated solutions of rodlike polymers. Even for a monodisperse system, the Doi theory yields two relaxation times, one corresponding to relaxation parallel to the director, the other transverse to it.