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Pigmented inks for inkjet printers, which consist of a solid coloured pigment dispersed in a solvent are a product in increasing demand worldwide. The stringent requirements on inks in terms of long lifetime and tolerance of a broad spectrum of stora~e conditions, as well as careful control over viscosity and wetting behaviour makes the formulation of stables inks challenging. To assist with designing successful ink dispersions, two polymers designed to act as dispersants for pigment were investigated. The focus of the investigation was to understand the adsorption behaviour of the polymers on to pigment surfaces, and how chemical factors affected this. To this end, the adsorption of polymers to a variety of surfaces was investigated, as were solution characteristics that could alter the effectiveness of the polymers as dispersants. The dispersant polymers were found to have a molecular weight of the order of 105 and to be negatively charged at high pH. When the charge was screened or neutralized then the polvrners would precipitate from aqueous solution. The dispersant polymers were found not to adsorb to the majority of surfaces investigated, including both charged and uncharged hydrophilic and hydrophobic surfaces, however they were found to adsorb to the organic, uncharged, hydrophobic polystyrene, suggesting they would be suitable for use stabilizing organic pigments.

Face à l’apparition croissante de troubles pigmentaires liés à l’exposition aux UV, le développement de nouveaux actifs blanchissants représente un enjeu majeur pour l’industrie cosmétique. De plus en plus de consommateurs s’orientent vers des produits eco-responsables, il devient urgent de développer de nouvelles méthodes de biocatalyse pour accéder à des antipigmentants. Certains glycosides, comme l’arbutine présentent des propriétés blanchissantes qui restent toutefois limitées face à l’hydrolyse rapide de la liaison O-glycosidique. L’enjeu du projet consiste à synthétiser des analogues de cette molécule en série thioglycosidique. En effet, cette liaison permet une plus grande stabilité vis à vis de l’hydrolyse. La mutation d’une glycosidase native issue de dictyoglomus thermophilum a permis d’accéder à une thioglycoligase. Cette dernière permet d’obtenir par catalyse enzymatique des analogues de l’arbutine. Six composés en série S- et O-glycosidique ont pu être synthétisés et testés en tant qu’agents dépigmentants. La méthodologie de synthèse a ensuite été appliquée pour l’obtention de thioglycolipides. Ces molécules sont connues pour leurs propriétés hydrogélifiantes permettant d’accéder à des matériaux thermoreversibles. Cinq molécules ont été identifiées en tant qu’agents hydrogélifiants. Les propriétés rhéologiques, thermiques et structurales ont été caractérisées mettant en évidence des différences significatives parmi les composés. Enfin les résultats préliminaires sur la formulation d’un produit à la fois antipigmentant et texturant s’avèrent prometteurs pour la validation d’un concept de matériau intelligent pour l’industrie cosmétique. / Considering the increasing appearance of pigmentation disorders caused by UV exposure, the development of new whitening agents is a major challenge for the cosmetics industry. Consumers are turning to ecoresponsible products, it is urgent to develop new methods of biocatalysis for the access to new depigmenting agents. Some glycosides, such as arbutin, have whitening properties which are still limited because of therapid hydrolysis of the O-glycosidic bond. The challenge of this project is synthesize analogues of this molecule in thioglycoside series. Endeed, this bond allows a greater stability against the hydrolysis. The mutation of anative glycosidase to dictyoglomus thermophilum gives access to a thioglycoligase. This makes possible the enzymatic synthesis of arbutine analogues. Six molécules were synthesized and tested as depigmenting agents. The synthesis methodology was then applied to the preparation of thioglycolipids. These moleculesare known for their hydrogellating properties allowing access to thermoreversible materials. Five molecules have been identified as hydrogellating agents. The rheological, thermal and structural properties have been characterized and showed significant differences depending of the compound structure. Lastly, the preliminary results on the formulation of a product that is both antipigmenting and texturizing are promising for the validation of an smart material concept for the cosmetic industry.