Preparation of hydrogel microcapsules: Effects of preparation conditions upon membrane properties

Abstract

Four types of hydrophilic gel microcapsules containing water have been prepared by an interfacial polymerization method. Each type of microcapsules has membranes of different compositions. By the combination of three kinds of monomers, N, N-dimethylacrylamide (DMAAm), 4-(aminomethyl)styrene (AmSt), and N, N-dimethylamino-propylacrylamide (DMAPAA), two types of water-soluble copolymers having tertiary amino groups were obtained. Two more types of copolymers were synthesized by copolymerization of above three monomers with α-acryloxy- ω-methoxy-poly(ethylene glycol) (a-PEG). These four types of copolymers were polymerized with terephthaloy-dichloride at the water/oil interface to prepare four types of microcapsules containing water. Effects of the stirring rate during the preparation of microcapsules upon the membrane properties were studied. The effects of relative permittivity of dispersing media on microcapsule sizes were studied. It was found that the microcapsule sizes are controlled by the composition of the membranes and by the relative permittivity of the solvents in which microcapsules are redispersed. Depending on the stirring rates during the preparation procedure, the different changes in microcapsule size were observed during the exchanges of dispersing media of various relative permittivities. From these results, it is concluded that different microcapsules in their membrane compositions and in their properties are obtained depending on the stirring rate during the preparation of microcapsules, even if other preparation conditions are kept constant.