Transient Rheological Behaviour of A Lyotropic Polymeric Liquid Crystal

Abstract

The stress transients resulting from step-wise changes in shear rate have been investigated for a liquid crystalline solution of PBLG in m-cresol. In step-up experiments these transients display a complex profile which includes multiple maxima, even in the Newtonian region. To a first approximation the curves scale with strain. A stepwise decrease in shear rate also causes a stress pattern with multiple maxima. The initial decay is related to the stress relaxation upon cessation of flow. Many of these features are not described by the existing theories. They are explained in terms of supermolecular structures such as domains.