Observation of deformation and recovery of poly(isobutylene) droplet in a poly(isobutylene)/poly(dimethyl siloxane) blend after application of step shear strain

The deformation and recovery of a poly(isobutylene) droplet with a lower viscosity embedded in a poly(dimethyl siloxane) matrix are directly observed from two directions after application of a large step shear strain. The droplet shape and recovery time strongly depended on the magnitude of the applied strain. Just after application of a large strain, a droplet deforms almost affinely to a flat ellipsoid. It then changes into a rodlike shape, a dumbbell, and to an ellipsoid of revolution, and finally to a sphere. Model calculations show that the primary driving force for the shape recovery is the interfacial energy in order to reduce the surface area of the deformed droplet. (C) 1998 The Society of Rheology.