Chemical modification of polysaccharides in aqueous media in order to generate new functional bio-based materials ; Modifications chimiques de polysaccharides en milieu aqueux pour générer de nouveaux matériaux biosourcés fonctionnels

Chemical modification of polysaccharides, by using processes conjugating efficiency and sustainability, is an appealing strategy to valorize biomass. Multicomponent reactions (MCR) are highly attractive functionalization routes, allowing for several precursors to be chemically linked in a one-pot manner, without catalysts or coupling reagents. We focused on carboxymethylcellulose (CMC), a widely available ether derivative of cellulose, which is water-soluble due to the presence of carboxylic acid functions that also facilitate its chemical modification, in particular by the MCR employed in this thesis. Two MCR were applied to CMC, namely the four-component Ugi reaction (U-4CR) and the three-component Passerini reaction (P-3CR), both carried out in water and under mild conditions. In particular, through the Passerini reaction we generated: i) a new family of functional and/or reactive derivatives based on CMC, concomitantly modified by ketones of various structures (unsubstituted ketones, pyruvate, acetoacetate, levulinate, diacetone acrylamide) and by an aliphatic isocyanide, as well as ii) CMC-based biohybrid materials, i.e. chemical and physical hydrogels. Thermosensitive chemically crosslinked hydrogels were obtained by a radical polymerization "grafting through" process, between a CMC macromonomer modified by Passerini with a methacrylate-functionalized ketone and ethylene glycol methacrylate-based comonomers. Physical hydrogels, also exhibiting a thermosensitive behavior, were generated from CMC grafted copolymers bearing both PEG-co-PPG (Jeffamine) segments displaying a LCST and aliphatic aldehydes. The thermosensitivity of these systems has been fully studied, and the impact of external and structural parameters has been elucidated by DSC, rheology and SAXS experiments. In particular, we have evidenced the benefits of the dual functionalization provided by the Passerini ligation. ; La modification chimique de polysaccharides, par des procédés conjuguant efficacité et durabilité, est une stratégie de choix ...