The effect of shear flow on the mesoscopic structure of partially miscible polymer blends

Abstract

Shear flow may have a significant effect on liquid mixtures such as polymer solutions but also polymer blends. The study of the effect of shear on the microscopic and mesoscopic structure of partially miscible polymer blends has recently been the focus of much theoretical and experimental work. Different theoretical approaches used to explain the observed shear induced enhancement or decay of concentration fluctuations in polymer blends are presented here and compared with the available data on several systems. In particular some of our most recent data for a polystyrene/poly(vinyl methyl ether) blend are presented. Our main conclusion is that, to describe all the phenomena encountered when shearing polymer blends, three sometimes competitive factors must be taken into account: the change in the equilibrium thermodynamics of the system due to molecular conformational changes, the coupling between concentration fluctuations and shear stress and the shear droplet break-up effect.