Introduction Viscosity is an important factor for the texture and quality of cosmetics and liquid products 1-11). In particular, stability during storage and usability of these products is greatly influenced by viscosity. Recently, addition of functional particles (e.g. fragrance capsules) and changing flow patterns with shear have been implemented to achieve a higher performance in liquid products. It is advantageous that the dispersion flow patterns change reversibly from the stable and steady state to the flow state with the use of shear. For the realization of these characteristics, structural viscosity should be rendered to dispersions, which consist of flow patterns in which the viscosity decreases with increasing shear rate. However, it is difficult to control the reversible nature of dispersion flow patterns. Generally, polymers and surfactants are used to control viscosity. An effective polymer used for increasing viscosity strongly binds to the water molecules and has an excluded volume in aqueous solution. When the polymer concentration exceeds the threshold, the excluded volume of the polymer begins to overlap and interpenetrate each other. Thus, polymers increase the viscosity three-dimensionally in the whole aqueous solution 12, 13) .

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