The first step of the project has entailed through bibliographic research to determine the appropriate polymers building blocks to be used for this project. These building blocks, either of natural or synthetic origin, have an assessed impact on environment and biodegradability as fundamental prerequisite. At the same time, commercial polymers with known biocompatibility and biodegradability profiles have been used for the proof-of-concept production of capsules, mainly via polymer self-assembly in aqueous environment. The appropriate methodologies have been adapted depending on the desired capsule morphology and size in the presence of the active to be encapsulated. Ultra-turrax homogenization, microfluidic techniques, spontaneous coacervation, and other methods have been considered. We have gained insights in the interactions between the polymers and the actives to be encapsulated, particularly some model perfume materials of natural origin, and the way these actives determine the capsule morphology, resistance to dilution, and stability over time. The physical-chemical characterization of these novel soft matter-based systems has been carried out by means of several available techniques, like several microscopy and scattering methods, to evaluate their morphology and physical properties, and to allow further optimization of the formation process.
The capsules have been introduced in model formulation media, in order to evaluate not only their stability in these concentrated surfactant solutions, but also the release mechanisms of the encapsulated actives. For example, the capsules obtained by means of coacervations can be easily disrupted to release their perfume payload by dilution, a process that can take place during the normal washing cycle of household washing machines. The release can be tracked using microscopy techniques also completed to microfluidics, and model fluorescent molecules mixed with the actives. The effect of medium composition, such as salt concentration, have been also investigated.
The microcapsules were tested for performance and deposition on various surfaces. At present, studies have been conducted on cotton and polyester fabrics. We observed that perfume molecules were deposited more on the hydrophilic cotton than on the hydrophobic polyester, with a further dependance on the molecular structure of the fragrance. This underlined once again the importance of the fragrant molecule’s nature not only on encapsulation but also on its deposition.
