Effect of dispersing medium on permeability of microcapsule membrane

• Published in: Colloids and surfaces, B, Biointerfaces B, Biointerfaces, 2003-07, Vol.30 (1), p.123-127
• Main Authors: Chang, Chih Pong, Kimura, Miho, Yamamoto, Takao, Nobe, Masahiro, Dobashi, Toshiaki
• Format: Article
• Language: English
• Subjects: Activation energy; Membrane; Microcapsule; Permeability; Release curve; Time constant
• ISSN: 0927-7765; 1873-4367
• DOI: 10.1016/S0927-7765(03)00079-1

Transfer of azo-dyes from dioctylphthalate core to binary mixtures of methanol+acetone with different compositions through poly(ureaurethane) (PUU) microcapsule membrane has been measured. The release curves were expressed by an exponential equation C( t)= C eq(1−exp(− t/ τ)) except for pure acetone, where C( t) is the concentration of the dye in the dispersing medium, C eq that at the equilibrium state, t the elution time and τ a time constant. C eq and τ are related to the chemical potentials and the diffusion coefficient of the dye, based on a simple theoretical model. The logarithm of τ was roughly proportional to the reciprocal of the absolute temperature, from which the activation energy E a for the transfer of the dye was estimated. The value of E a observed using acetone as the dispersing medium was much larger than that observed using methanol. In the curve of τ versus percentage weight of acetone w in the dispersing medium, a minimum was observed around w∼40%. The release curve for pure acetone had multi steps and did not agree with the theoretical prediction. These characteristic permeability properties were attributed to a structural change of the microcapsule membrane surface due to the interaction of the protective colloid and the dispersing medium.