La défense publique de la thèse de Monsieur Manuel Reche Tamayo aura lieu le 12 juillet 2021 à 15h par vidéo-conférence, le lien actif sera publié la veille sur ce site.

Promoteur de thèse: Monsieur Patrick Brocorens
Co-promoteur: Mme Laurence Bouteiller (Sorbonne Université)

Résumé de la dissertation:
This work deals with supramolecular organogels. These gels are obtained by dispersing in the organic solvent low molecular weight molecules (Low Molecular Weight Gelators, LMWGs), which are not soluble at room temperature and form a suspension. This suspension is heated, achieving solution, and cooled down back to room temperature where LMWG molecules self-assemble in non-covalently bonded Self-Assembled Fibrillar Networks (SAFiNs), e.g., by hydrogen-bonding, π-stacking, Van der Waals interactions, etc. This entangled network traps mechanically the liquid, principally by surface tension, triggering a gel state.

A precise description of the phenomena remains partially unknown, leaving open questions that still impede to predict beforehand whether a given LMWG candidate will be able to gelate a certain liquid of interest. If design rules could be established between the chemical structure of a LMWG and its gelation properties, it could be possible to design LMWGs for specific liquids of interest while providing insight about organogel formation. Thus, this work investigates sets of chemically diverse LMWG families, with the aim of correlating their chemical structure with their corresponding gelation behavior.

The approach followed in this thesis consists in modelling the self-assembly of different series of LMWGs, bisamide-cyclohexane compounds and thiazole compounds with alkyl chains of different lengths, with the aim of understanding the formation of the gel fibers and determining their structure. Most of the LMWGs that we have studied crystallize to form gels, and for such crystalline systems, our methodology starts with a Crystal Structure Prediction (CSP) of the gel fibers, combining crystal cell generation and powder X-ray diffraction simulations. Then, we determine their crystal morphology using growth kinetics principles, to finally characterize the gelation ability of the gel fibers using surface energy parameters and Hansen solubility parameters. Our modelling activities have been carried out in very close interaction with corresponding experimental efforts undertaken in the groups of Prof. Laurent Bouteiller (Sorbonne Université) and Prof. Pierre-Antoine Albouy (Université Paris-Sud). Their results of gelation experiments, powder X-ray diffraction and SEM characterization were compared with our modelling data.