Papers by Author: Takao Yamamoto

Abstract: We have prepared W/O/W-type microcapsules with polyureaurethane wall membrane and aqueous core containing methylene blue by means of the double emulsification method and the effect of the rate of agitation at the twice emulsification on the release of methylene blue to dispersing methanol was examined. The release curve was expressed fairly well by the streched exponential form: where C(t) and C_eq are the concentrations of methylene blue in the dispersing methanol at time t and at the equilibrium state, respectively. The time constant τ increased and the exponent α decreased with increasing the rate of agitation at the second emulsification, whereas τ decreased and α was constant with increasing the rate of agitation at the first emulsification. These differences are discussed from a viewpoint of inhomogeneity of the microcapsule wall membrane.

Abstract: We have prepared an anisotropic hydrogel with birefringence by means of dialysis method and analyzed the dynamics of the gel-forming process using purified chitosan with the degree of deacetylation at 100%. The dynamics was expressed well by a theory based on “moving boundary picture”(Nobe, Dobashi and Yamamoto, Langmuir 2005).