Investigation of relationship between flow pattern and phase separation structure in a liquid mixture layer using EHD convecttion

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We have investigated the relationship between the flow pattern based on electrohydrodynamic (EHD) convection and phase separation structure in a polymer blend film. In the present study, the solvent evaporation and thermal quench of polymer blend solutions were adopted to induce the phase separation in the film.In the former method, we have investigated the effect of EHD convection on the domain structure in a polystyrene (PS)/polyvinylacetate (PVA) blend film to demonstrate the feasibility of using the EHD effect as a means of mixing and morphology control in a polymer blend film. Here, polymers-toluene solutions were spread on a glass substrate with patterned electrodes to apply a dc electric field, and well-defined structures of EHD convection were formed in the polymer solutions. As a result, regular patterns were formed in the PS/PVA polymer blend him in which PVA-rich domains were confined within each unit of patterned electrodes, i.e.,between positive and negative electrodes, at an appropriate electric voltage. Also, it was demonstrated that such novel morphology are not due to the wetting/dewetting effect of polymer components to the Pt electrodes deposited on the glass substrate, by experiments with a SiO_2-covered substrate.In the later case, since we had some problems in the experimental apparatus and procedure, unfortunately we could not obtain the available results.In addition, we have developed the numerical simulation code of the phase separation based on the Cahn-Hilliard model with a hydrodynamic effect, and then clarified the effects of the capillary force, gravity force and temperature gradient on the phase separation structure.