Electrorheological properties of a type-I immiscible polymer blend: Scaling and structural changes

le studied the electrorheological properties of a type-I immiscible polymer blend, in which droplets of liquid crystalline polymers are dispersed in a polydimethylsiloxane under no electric field. We measured flow curves of the blend at various applied electric fields under various temperatures, and made optical observations of the structure. Two anomalies were found in the flow curve, indicating that there should be three different structures, which are designated as N, A, and B in the order of increasing shear rate. A is much higher than B and N in viscosity. By optical observations it was clarified that A and B coexist in a certain range of shear rate and there is a sharp boundary between them. In A wt found a scaling relation in the flow curve and a dimensionless number Mn', which is the only one parameter characterizing the state of A. (C) 1999 The Society of Rheology. [80148-6055(99)01201-8].