Abstract
Poly (phthaloyl L-lysine) microcapsules were prepared by interfacial polymerization techniques and treated by lecithin. Various mono-, di-, and trivalent cations were found electrophoretically to be bound by both intact and lecithin-treated poly (phthaloyl L-lysine) microcapsules dispersed in aqueous media. In both cases, cation binding was stronger with ions of higher valency and charge reversal of the microcapsules was observed at high concentrations of polyvalent cations. However, the treatment of the microcapsules with lecithin caused appreciable changes in the zeta-potential and cation binding of the microcapsules. That is, the zeta-potential was less negative and the cation concentration needed to produce the charge reversal was lower for the lecithin treated microcapsules than for the intact microcapsules. The zetapotential was converted into the surface charge density by means of a modified Gony-Chapman equation. Finally, the free energy of cation binding was evaluated from the surface charge density as a function of the cation concentration using Stern's adsorption theory.
