Soft Matter Complex Systems as Model Biological Systems

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In this project, we investigated the structure formation of Soft Matter Complex Systems as Model Biological Systems. Especially we focused on the following three complex systems, which may have relation to the biological functionalities.1)Liquid crystal + polymer complex system :Biopolymers having anisotropic shapes, such as protein, virus and actin-filament, forms characteristic aggregates in the biological circumstance. The basic attractive interaction between the anisotropic particles may be originated from the so-called depletion interaction. In this study we found that the rigid polymer enhances the depletion interaction about 1000 times compared with the case of coil-like polymer chains. This is due to the large effective excluded volume of the rigid polymer chains.2)Surfactant membrane + polymer chain (colloidal particle) system :We have investigated effects of a guest component (polymer or spherical colloidal particle) confined between flexible lamellar slits on the inter-lamel … More lar interaction. The addition of the neutral polymer into the lamellar phase induces an attractive inter-lamellar interaction. On the other hand, the spherical colloidal particles confined between the flexible lamellar membranes reduce the undulational fluctuations of lamellae and bring a repulsive inter-lamellar interaction.3)Polymer grafted surfactant membranesWe have investigated the effects of grafted polymer chains on the bending modulus and the inter-membrane interactions of lamellar membranes. The bending modulus of the polymer grafted membranes increases in proportion to the square of the end to end distance of the polymer chain. The mushroom layer is renormalized to the membrane thickness, which enhances the repulsive Helfrich interaction. When the size of the decorated polymer chain increases to the inter-lamellar distance, however, the mushroom is squeezed so as to optimize the inter-lamellar potential. Further increase of the grafted polymer size brings a lamellar-lamellar phase separation. Less