Can only rheology be used to determine the phase separation mechanism in dynamically asymmetric polymer blends (PS/PVME)?

Abstract

We investigated theoretically and experimentally the correlation between the time evolution of different phase-separating morphologies and corresponding linear and transient rheological behaviors for the dynamically asymmetric PS/PVME (polystyrene/polyvinyl methyl ether) blend in which there is a large difference between the glass transition temperatures of the pure components (about 125 °C). The sensitivity of different rheological analyses was examined to distinguish different phase separation mechanisms from each other, including nucleation and growth (NG), spinodal decomposition (SD), and viscoelastic phase separation (VPS). We found that a combination of experimental and theoretical studies of the linear and nonlinear rheology could provide satisfactory criteria to distinguish effectively samples phase separating by different mechanisms. Furthermore, the variation of fractal behavior by phase separation time was investigated for interconnected and percolated network structures induced by SD and VPS, respectively, which suggested that both network structures are controlled by a diffusion-limited cluster aggregation (DLCA) mechanism.