Rheology and morphology of phase-separating polymer blends

Simulations of phase separation under oscillatory shear flow have been performed based on the time-dependent Ginzburg-Landau (TDGL) equation. To calculate the stress tensor, the expression proposed by Kawasaki was used. The results of the simulations have been confronted directly with experimental results on a LCST blend of P alpha MSAN/PMMA to evaluate the potential of the simulations. The effect of quench depth, shear amplitude, and shear frequency on the morphology development as well as on the corresponding rheological properties has been investigated. The results show that the characteristic rheological behavior of phase-separating systems can be attributed to the interfacial relaxation, which is changing during the process of phase separation. The strength of the concentration fluctuations and the interfacial volume fraction are key factors determining the contribution of interfacial relaxation to the global rheological behavior of the blend. In the low frequency range, the oscillatory shear cannot affect the critical paint, but it can accelerate the coagulation and growth of the blend morphology. The simulations qualitatively agree with the experimental findings.