Permeability of azo-dye through poly(urea-urethane) microcapsule membrane

Transfer of azo-dyes from dioctylphthalate to methanol through poly(urea-urethane) microcapsule (PUUMC) membrane has been measured. The release curves are expressed by an exponential equation C-s=C-infinity(1-e(-t/tau)), where C, is the concentration of the dye in methanol, C-infinity that at the equilibrium state, t the elution time and tau is a time constant. C-infinity and tau are related to the chemical potentials and the diffusion coefficient of the dye, based on a simple theoretical model. The relationship between tau and the absolute temperature exhibits non-Arrhenius behavior at high temperatures. The non-Arrhenius behavior is explained on the basis of the chemical potential effect on tau. At low temperatures, tau exhibits the Arrhenius behavior. From a semi-logarithmic plot of tau versus the reciprocal of the absolute temperature in the low temperature region, the activation energy for the transfer of the dye is estimated. (C) 2002 Elsevier Science B.V. All rights reserved.