New types of pattern formation caused by the competition between non-equilibrium phenomena

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Usually pattern formation is accompanied by nonequilibrium phenomena such as phase separation. If more than two nonequilibrium phenomena are coupled with each other, new types of pattern formation are expected. The final morphology obtained by competition between two nonequilibrium phenomena cannot be predicted by an equilibrium phase diagram, or thermodynamically. It is kinetically determined by competition between two nonequilibrium processes. Competition between nonequilibrium phenomena should provide us with new types of morphologies, which can never be obtained by single ordering process. In principle, the phenomena should be predicted by coupled equations describing nonequilibrium phenomena. The nonlinear and nonlocal characters of the equations make the theoretical prediction difficult. We have studied this complicated, but important phenomena both experimentally and theoretically. We have used the digital image analysis (DIA) method developed by us for studying pattern formatio … More n dynamics.The coupling phenomena studied were as follows: (1) Phase separation and crystallization, (2) phase separation and chemical reaction, and (3)phase separation and wetting. In case (1), we have found the pinning of phase separation by solidification and also the banded structure of spherulite induced by phase separation. In case (2), it has been demonstrated that the relation between the chemical reaction speed and the phase separation speed dominates the pattern evolution and the interface structure of domains. If chemical reaction between two component polymers proceeds more slowly than phase separation, chemical reaction should occur most efficiently at interface and modified interface can probably be formed. In case (3), we have found that the geometrical confinement strongly affects the pattern evolution and the resulting structure. The dynamics of pattern formation under the wetting effect has mostly been clarified.In this research, we have aimed at understanding the basic physics of pattern formation under competition between two nonequilibrium phenomena and developing new methods for morphology control. Recently it has been well established that there is strong correlation between morphology of heterogeneous polymer alloy and its physical properties. From this aspect, the morphology control is one of the most important techniques for designing the semi-macroscopic structure of polymer alloy with desired physical properties. Basically the above new types of morphology-control techniques should be applicable even for immiscible polymer blends without phase diagrams. In that case, the competition between mechanical mixing process and other nonequilibrium phenomena such as chemical reaction should be considered. We hope that this study will provide us with new techniques of morphology control and new classes of materials. Less