LEPMI - Rubrique Présentation 2022

PH'D Defense M Saman SALIMI

M Saman SALIMI will present his thesis "Experimental characterization and modelling of OAPS as a precursor for polyOAPS-imide membranes".
Abstract : Gas separation by dense polymer membranes is a promising alternative to the cryogenic distillation or adsorption separation processes due to its much lower energy costs. Unfortunately, polymers tend to lose their structural integrity at high temperatures. To improve the thermomechanical resistance while maintaining the gas-sieving properties, hybrid ultrathin membranes based on inorganic POSS (polyhedral oligosilsesquioxanes) cross-linked with organic imides have recently been developed using interfacial polymerization. These polyPOSS-imide membranes were indeed found to perform under tougher operating conditions than conventional polymers. However, the aliphatic arms of the inorganic POSS precursors used so far were too flexible and prone to thermal degradation.

This work aims to attain more stable hybrid membranes using a new inorganic POSS precursor, the octa(aminophenyl)silsesquioxane (OAPS). This siloxane-based cage has three different isomers depending on the meta, ortho and para position of the amine with respect to the phenyl group. An extensive literature search showed that the isomer ratios were not clearly defined and that several synthesis routes gave different results. This is problematic as the nature of the isomer will strongly affect the resistance and gas selectivities of the resulting membranes. Experimental characterizations including picnometry, infrared spectroscopy (IR), 1-dimensional and 2-dimensional nuclear magnetic resonance (NMR) have been performed for a commercial OAPS containing all three isomers and a controlled OAPS containing only the para and meta isomers. To better identify the isomers, the experimental results were compared to predictions of the IR and NMR spectra by quantum mechanical methods such as Density Functional Theory and by machine-learning methods such as MestreNova. OAPS was then used as a precursor to make new hybrid membranes with increased thermoresistance. These polyOAPS-imide membranes were characterized using IR, thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and permeability measurements. They were found to degrade well over 400°C and to preserve gas selectivity of more than 10 for H2/CH4 and H2/N2 at 200 °C. In parallel, a force-field was developed to carry out molecular dynamics simulations of the three OAPS isomers in order to characterize their differences at the atomic level.

Supervisor : Mme Sylvie Neyertz-Brown

Jury members :
Sylvie NEYERTZ-BROWN Maîtresse de conférences Université Savoie Mont-Blanc Directeur de thèse
José SANCHEZ-MARCANO Directeur de recherche Institut Européen des Membranes - UMR 5635 Rapporteur
Catherine MARESTIN Chargée de recherche Université Claude Bernard Lyon 1 - IMP-INSA UMR5223 Rapporteur
Lionel FLANDIN Professeur des universités Université Savoie Mont-Blanc Examinateur


Date infos
Thesis Defense 29 March 2022  10H30
Address of the thesis defense :  IUT de Chambéry - Université Savoie Mont Blanc 28 Av. du Lac d'Annecy 73370 Le Bourget-du-Lac - Salle des Conseils