Rheology of polymeric liquid crystals

Recent developments in the theoretical understanding of the rheology of polymeric liquid crystals include the contribution of viscous and textural forces, the mathematical structure of the molecular theory and possible constitutive equations for these materials. At the same time the role of the various forces has been determined experimentally in different ways. The variable microstructure during flow and after stopping the flow has been studied by means of scattering techniques in which light, X-rays and neutrons have been used to supplement rheological techniques. A more complete and complex picture is now emerging for the flow-induced texture over a wide range of shear rates and the concentration range from the isotropic-->nematic transition up to the melt. Whereas previous results referred to main chain liquid crystals, new results on side chain polymeric liquid crystals have elucidated the contributions of the mesogenic side groups and the flexible backbone.