Simultaneous emulsification and interfacial polycondensation for the preparation of colloidal suspensions of nanocapsules

Sub-micrometric particles having an oil core and a polymer shell (nanocapsules) have been prepared by combining in a single stage the emulsification process and an interfacial polymerization reaction. The spontaneous emulsification produced very fast a dispersion of oil droplets of 100–400 nm mean diameter at the surface of which the subsequent polycondensation reaction took place. The process has been optimized with respect to the choice of α-tocopherol as the oil and made robust regarding the presence of monomers in the aqueous and oil phases and their conversion into polymers. The major cause of troubles was the large concentration of diol or diamine monomers in the aqueous phase that made the oil droplets unstable with respect to aggregation immediately after their formation. Once the emulsifier has adsorbed and the polymerization has completed, the final suspensions of nanocapsules were quite stable over long periods. A secondary population of micrometric particles that coexisted with the nanocapsules was present in several cases, which was unfavourable regarding their application as a drug delivery system for cosmetic applications.