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 PRMSAN/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 point, but it can accelerate the coagulation and growth of the blend morphology. The simulations qualitatively agree with the experimental findings.
The phase behavior of the ternary system consisting of the hydrophilic ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF 4 ), toluene and ethanol was investigated. Single-phase microemulsion and multiphase regions were observed in the ternary phase diagram. To the best of our knowledge, this is the first report on nonaqueous IL microemulsions prepared in the absence of traditional surfactants. The microstructures and structural transitions of the microemulsion system were investigated by cyclic voltammetry, pulse field gradient spin-echo nuclear magnetic resonance and electrical conductivity measurements. The microemulsions exhibit IL-in-toluene (IL/O), bicontinuous (BC) and toluene-in-IL (O/IL) microstructures, similarly to traditional surfactant-based microemulsions. The three kinds of microstructures were confirmed from freeze-fracture electron microscopy observations. A pearl necklace-like structure was observed in the BC microemulsion. The polarity of bmimBF 4 domains in the IL/O microemulsion was investigated by UV-visible absorption spectroscopy using methyl orange as a probe. It was found that the polarity was lower than that of the bulk bmimBF 4 , and it increased with increasing bmimBF 4 content at a constant toluene-ethanol ratio.
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