Microencapsulation of Aqueous Compounds Using Hexamethylenediamine and Trimesoyl Chloride: Monodisperse Capsule Formation and Reaction Conditions on Membrane Properties

Efficient microencapsulation of aqueous compounds for dispersion in aqueous media remains challenging. To prepare aqueous microcapsules, we employed interfacial polymerization with hexamethylenediamine (HMDA) and trimesoyl chloride (TMC), which are commonly used for the formation of impermeable reverse-osmosis membranes. We employed an emulsification technique based on a high-viscosity external phase and uniform shear fields to produce monodisperse aqueous drops on the order of 10 mu m. The effects of shear stress and HMDA concentration on the drop sizes were studied. The HMDA amount and emulsion drop size were both found to be important for subsequent capsule formation. The stoichiometric ratios of amine to acid chloride affected both the redispersibility of the microcapsules and the release rates of Coomassie Brilliant Blue (Coomassie Blue). Although high encapsulation efficiencies were achieved, the release rate varied with the sizes of the encapsulated molecules/ions. Optimum capsule formation and control of release were obtained with a stoichiometric ratio [c(NH2)/c(COCl)] of 5.