Stimuli-responsive membranes for targeted delivery of actives
- Autores: Rita del Pezzo
- Directores de la Tesis: Marta Giamberini (dir. tes.), Johan Smets (codir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2020
- Idioma: español
- Tribunal Calificador de la Tesis: Veronica Ambrogi (presid.), Bartosz Tylkowski (secret.), Cristina Acebo Gorostiza (voc.)
- Programa de doctorado: Programa de Doctorado en Nanociencia, Materiales e Ingeniería Química por la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
In this work the attention will be mainly drawn on the design, the preparation and the characterization of light sensitive microcapsules, which are able to release the payload under white light irradiation. Although the main reason for encapsulation is the necessity to store and protect an active ingredient into a physically and chemically stable shell, in commercial applications can be important also to control the release over time and to drive it in a specific place and in a specific moment. This is the main reason why we want to develop an easy, cheap and robust chemistry to produce capsules responsive to external stimuli. Among other external stimuli light was selected to control the release of fragrances and optimize it overtime, boosting the release during day-life and deactivating it during night. For this purpose, the core-shell capsules morphology was found to be the most suitable, and the azobenzene, among other chromophores, was selected as photo-isomerizable unit and building block of the capsule’s polymeric shell. Azobenzene derivatives in fact, were designed and synthesised to be incorporated in the capsule’s shell as its main constituent. The design included the functionalization of un-modified azobenzene with proper side groups which allow the isomerization of the whole molecule to undergo with white light, and subsequent incorporation of the new light-sensitive unit into different systems as polymeric linear chains or crosslinked nets.
First, the synthesis and characterisation of the photosensitive azobenzene units will be discussed and analysed; their behaviour, as a consequence of exposure to white light, will be investigated. The synthesis and characterization of linear polymeric chains and crosslinked polymers, both containing the synthesized photosensitive azobenzenes, will be examined and debated in depth.
The preparation of microcapsules based on such photosensitive systems will also be explored in the following sections of this work; the microcapsules are filled with perfumes which have business interest and importance. In some cases, the applicability of such microcapsules in consumer good products is also explored and consumer tests are designed and conducted.
The study of the controlled and triggered release of the active has been carried out in aqueous environment and evaluated mainly via dynamic head space measurements (DHS). Via DHS it is possible to identify and measure what is released from capsules, in a controlled volume, over time and after exposure to different conditions as light or UV irradiation, temperature, aggressive components, pH variations, etc. In this work the aqueous solution was selected as the least aggressive environment for capsules and for the active encapsulated, if compared with real life finish products which always contain a certain amount of surfactants; surfactants in fact, due to their amphiphilic nature, may force the encapsulated active to leak out from the capsules and thus, what is measured with the DHS, would not only be the active released due to light irradiation but also the one released due to forced leakage.
