Rheology and morphology of phase-separating polymer blends

Simulations of phase separation under oscillatory shear flow have been perf ormed based on the time-dependent Ginzburg-Landau (TDGL) equation. To calcu late the stress tensor, the expression proposed by Kawasaki was used. The r esults of the simulations have been confronted directly with experimental r esults on a LCST blend of P alpha MSAN/PMMA to evaluate the potential of th e simulations. The effect of quench depth, shear amplitude, and shear frequ ency on the morphology development as well as on the corresponding rheologi cal properties has been investigated. The results show that the characteris tic rheological behavior of phase-separating systems can be attributed to t he interfacial relaxation, which is changing during the process of phase se paration. The strength of the concentration fluctuations and the interfacia l volume fraction are key factors determining the contribution of interfaci al relaxation to the global rheological behavior of the blend. In the low f requency 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.