Kinetics of structural transitions in polymeric systems ・・・properties of gyroid structure・・・

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A cooperative research was carried out on block copolymers by Hasegawa group, on water and surfactant mixtures by Imai group and the theoretical investigation by Ohta-Nonomura group. Ohta and Nonomura studied the fundamental properties of the formation and the stability of the gyroid structure which is one of the characteristic features of soft matter.They applied the mode expansion method and computer simulations and found that Fddd structure as well as the ordinary mesoscopic structures is a stable thermal equilibrium structure whereas perforated lamellar structure is metastable. It was also found that Fddd structure appears also in the course of the transitions between gyroid structure and lamellar structure where the cubic symmetry of gyroid is broken. It is emphasized that these theoretical predictions are consistent with the experiments of Hasegawa group who carried out X-ray scattering and found a series of morphological transitions from lamellar, Fddd and gyroid structures. The experiments of Imai group showed that the transition kinetics in water/surfactant systems are quite different from those of block copolymers. Therefore, we need further theoretical and experimental investigations to clarify the universal features of the dynamics of soft matter.