Rheological properties of polymer blends with sphere-in-sphere morphology

The linear viscoelastic behavior of polystyrene (PS) and poly(methylmethacrylate) (PMMA) blends with PS as the matrix and amounts of PMMA in the range 10–30 wt% was investigated. Transmission electron microscopy (TEM) revealed a complex morphology which was characterized by the existence of composite particles; the PMMA particles which are enclosed in the PS matrix themselves carry PS inclusions. In order to explain the G* data of these blends a model is presented which consists of a Palierne model for the composite particles and a Palierne model for the whole blend, taking into account composite and neat particles. Simulations show the principal relevance of the assumptions made. Moreover, it is shown that the measurements agree well with the model for the whole measured frequency region and that the fit parameters, the size of the composite particles and the concentration and size of interior particles are in reasonable agreement with data available from TEM. Received: 1 November 1998 Accepted: 5 April 1999