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 Cs=C∞(1−e−t/τ), where Cs is the concentration of the dye in methanol, C∞ that at the equilibrium state, t the elution time and τ is a time constant. C∞ and τ are related to the chemical potentials and the diffusion coefficient of the dye, based on a simple theoretical model. The relationship between τ 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 τ. At low temperatures, τ exhibits the Arrhenius behavior. From a semi-logarithmic plot of τ versus the reciprocal of the absolute temperature in the low temperature region, the activation energy for the transfer of the dye is estimated.