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Séminaire MCMF

Vendredi 25 septembre à 14h30,
Salle Erwin Bertaut, F418.

Orateur : John Bartlett (Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore, QLD, Australia)
“Cooperative Physical and Chemical Interactions for the Sol-Gel Processing of Organised Films and Nanoparticles”

Abstract

This presentation will explore the use of self-assembly and cooperative physical and chemical interactions for controlling the structural evolution of organised nanohybrid films and nanoparticles via sol-gel processing. The underlying physical and chemical processes will be illustrated through a number of examples.

In the first series of examples, the production of thin films of self-structured silsesquioxane nanohybrids by spin coating, through the sol-gel hydrolysis and condensation of bridged organosilanes bearing self-assembling urea groups, will be described. The resulting nanostructures are shown to be dependent on the type of catalyst used (nucleophilic or acidic), and are further modulated by varying the deposition conditions. FTIR studies revealed the presence of highly organized structures due to strong hydrogen bonding between urea groups and hydrophobic interactions between long alkylene chains. The preferential orientation of the urea cross-links parallel to the substrate is shown using polarized FTIR experiments. A mechanistic model is described to explain such long-range structuring under far-from-equilibrium conditions.

In the second series, a new approach for producing metal oxide nanoparticles via sol-gel processing in reverse micelles is explored, in which the chemical and physical properties of the polar aqueous core of the reverse micelles are modulated by the inclusion of a second polar co-solvent. The co-solvents were selected for their capacity to solubilise compounds with low water solubility (suitable for the encapsulation of species such as oncology drugs) and included DMSO, DMF, EG, n-PrOH, DMA and NMP. A broad range of processing conditions are elucidated that are suitable for preparing nanoparticles with dimensions of 50 nm to 500 nm. In contrast, only a relatively narrow range of processing conditions were suitable for preparing nanoparticles in the absence of the co-solvents, highlighting the key role of the co-solvent in modulating the properties of the polar core of the reverse micelles. A mechanism is described that links the interactions between the various reactive sites on the polar head group of the surfactant and the co-solvent to the nucleation and growth of the nanoparticles. The use of this strategy for encapsulating drugs with low water solubility such as 3-hydroxyquinolinone derivatives, for potential applications in oncology drug delivery will be discussed.

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