Elaboration of double emulsion-based polymeric capsules for fragrance

Abstract

We aim at encapsulating fragrances made of a variety of lipophilic species to slow down their diffusion. Our strategy is to develop capsules by polymerizing the water intermediate phase of an oil-in-water-in-oil double emulsion. In other terms, our system consists in a direct emulsion of fragrance (O1) in a water phase (W) containing monomer, initiator, and cross-linker. To obtain the double emulsion, this direct emulsion, stabilized by a hydrophilic surfactant, is itself dispersed in an external lipophilic solvent used in perfumery (O2) and stabilized by a lipophilic surfactant. Polymerization of the intermediate water phase aims at obtaining a 3D network. Differently from nowadays-proposed capsules, this strategy allows polymerization only taking place in the water phase rather in the phase containing the fragrance. Moreover, the obtained 3D network is supposed to play the role of an effective barrier limiting the diffusion of the inner lipophilic species towards either the external solvent or air. Such an approach implies the combination of a formulation step to elaborate the double emulsion using two antagonistic surfactants, a hydrophilic one and a lipophilic one, and of the polymerization of the intermediate phase. Insertion of the polymerizable species in the double emulsion shall not destabilize it. Some monomers exhibiting interfacial affinity and interfering with the formulation of the double emulsion have to be avoided. By varying the nature of the monomers and the cross-linker to monomer ratio, capsules with high encapsulation efficiencies and with various mechanical properties have been obtained.