Kinetics of coarsening in immiscible poly (ε-caprolactone)/ poly(styrene-co-acrylonitrile) blends

Abstract

The morphological development of immiscible blends of poly(ε- caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) during static annealing was studied using time-resolved light scattering and optical microscopy. In the melt-blended samples, coarsening was not observable at low temperatures, even above the glass transition temperature of SAN (T g=113 °C). It occurred when a critical temperature T* (for example, 170 °C for a PCL/SAN (50/50) blend) was reached. T* was found to have a strong dependence on the blend composition, and we suggest that this results from an effect of the large difference in viscosities of pure PCL and SAN on the particle collision rate. The morphological development of solution-prepared blends was found to differ greatly from that of the melt-blended samples. At first, spinodal decomposition (SD) began, and then collision kinetics prevailed over SD. After the particles grew to a size of approximately 10 μm, secondary SD took place and small domains (∼1 μm) appeared in both the matrix and the particles. Consequently, the overall coarsening behavior varied significantly from the predictions of current theories. © 2012 The Society of Polymer Science, Japan (SPSJ) All rights reserved.