Development of the method to analyze the two-dimensional molecular dynamics at the soft interface

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The aim of the research is to develop the analytical tools to measure the dynamics at the interface related to the soft materials such as liquid interfaces and biological membranes. Quasi-elastic laser scattering (QELS) has been applied to the study on the surface of imidazolium salts (room temperature ionic liquids) - water system. The surface stress, taken by QELS, reflects the molecular behavior at the surface. The change of the surface stress has been measured and its dependence on molar ratio of imidazolium salts to water can be clarified. It has been concluded that the transient interaction of cations and anions takes place. Further, we have succeeded in the measurement of the interfacial stress of the black lipid membrane, which consisted of two lipid layers. The addition of the surfactants induces the change of the membrane structure and it is found that QELS is a powerful tool to take the structural change of the black lipid membranes.As another analytical tool, Brewster angle microscope has been developed using a high N.A. objective lens. The Brewster angle reflection takes place in the objective lens, so that the lateral resolution is enhanced up to less than 1 μm. Combined with the total internal reflection fluorescence microscope, it has been applied to the study on the phase transformation of lipid membrane.