Encapsulation by interfacial polycondensation. I. The capsule production and a model for wall growth

Abstract Capsules are produced by the interfacial reaction of terephthaloyldichloride, TDC, (dissolved in dibutylphthalate) and diethylenetriamine, DETA, (dissolved in the aqueous phase) at the interface of drops of the organic phase dispersed in the aqueous phase. The membrane produced exists of a top-layer and a sub-layer as in asymmetrical membranes. A model which relates the growth of the capsule wall and the concentration of TDC inside the capsule with time, is presented. For a spherical capsule the model shows both for wall thickness and TDC concentration a linear relationship with √t after the formation of a top-layer. The sub-layer is formed from cellular pores, whose walls are formed around droplets at the organic side of the membrane. The pore size increases from the initial interface into the capsule.