Permeability of dye through poly(urea-urethane) microcapsule membrane prepared from mixtures of di- and tri-isocyanate

Poly(urea- urethane) microcapsules were prepared by the interfacial polymerization with using mixtures of tri- and di-isocyanate monomers as wall forming materials, and dioetyl phthalate containing an oil-soluble dye as a core material. The time course of the dye release in dispersing tetrahydrofuran was measured as a function of the weight fraction of tri-isocyanate monomer in the total monomer W and the core/wall material-weight ratio g. The dye release curves were well represented by an exponential function C = C-eq(1 - e(-1/tau)), where C is the concentration of the dye in the dispersing medium, C-eq that at equilibrium state, t the elution time and tau is a time constant. tau increased linearly against w at high g, suggesting controllability of the release rate of microcapsules by varying tri-isocyanate/di-isocyanate ratio. (c) 2005 Elsevier B.V. All rights reserved.