Ce travail de thèse porte sur la synthèse et l'étude physico-chimique de polymères associatifs hydrosolubles à associations complémentaires. Utilisant la chimie covalente réversible, ce système met en jeu l'association d'un poly(diol) et d'un poly(acrylamide) partiellement hydrolysé portant des fonctions d'acide boronique. Ces dernières sont introduites par une technique de greffage qui a été optimisée et finement caractérisée. Le mélange des deux polymères permet d'obtenir des solutions visqueuses et des gels dynamiques et ceci pour de faibles concentrations. La possibilité de viscosifier des formulations en-dessous de la concentration de gélification constitue un résultat marquant qui distingue ce système de nombreux polymères à association hydrophobe. Dans le régime de gel, les propriétés rhéologiques linéaires sont analysées en relation avec l'étude de la force des interactions moléculaires qui ont été mesurées par la RMN du bore et une technique de fluorescence. La rhéologie non-linéaire apporte des informations essentielles sur la relation entre le cisaillement et la structure du réseau réversible formé. L'utilisation d'un système de visualisation de l'échantillon sous écoulement permet l'observation d'effets locaux fortement non-linéaires. L'influence des différents paramètres, comme le pH et la température, sur les propriétés dynamiques des solutions peut être rationalisée et modélisée en termes de lois d'échelles. L'originalité de ce concept de système associatif par associations complémentaires est mise en perspective au travers d'une revue de la littérature rationalisant le lien entre architecture et rhéologie des polymères associatifs hydrosolubles. / This thesis deals with the synthesis and the physical chemistry study of water-soluble complementary associative polymers. Based on reversible covalent chemistry, this system brings into play the association of a poly(diol) and of a partially hydrolyzed poly(acrylamide) bearing boronic acid moieties. The latter are introduced by a grafting technique which has been optimized and finely characterized. The mixing of these two polymers allows obtaining viscous solutions and visco-elastic gels at relatively low polymer concentrations. The possibility to make formulations viscous below the gel point represents a remarkable result, which differentiates this system to numerous associative polymers based on hydrophobic interactions. In the gel regime, the linear rheological properties are analyzed with regard to the strength of molecular interactions which have been measured by boron NMR and a fluorescence technique. Non-linear rheology brings essential information about the relationship between shearing and the structure of the formed reversible network. The use of a visualization setup of samples under flow enables the observation of very non-linear local effects such as wall slip and shear-banding. The influence of various parameters, as pH and temperature, on the dynamical properties of solutions and gels can be rationalized and modeled in terms of scaling laws. The originality of this concept of associative system with complementary associations is put into perspective through a literature review on the relationship between architecture and molecular interactions on one hand, and rheological properties of associative polymers on the other hand.

<p>Highly shear-thinning polymers that can easily flow upon the application of shear but form gels at rest have multiple potential applications in the eye. In the front of the eye, a formulation that can easily be administered via a conventional eye dropper but form a gel within the tear film once applied would be beneficial for prolonging drug release at the front of the eye, either alone or as a medium for entrapping nanoparticles or nano-objects loaded with drugs. In the back of the eye, vitreous substitutes that can be administered through a narrow gauge needle (and, ideally, removed via the same) may be beneficial for retinal surgeries.</p> <p>The overall objective of the proposed research is to chemically modify PVP through grafting strategies to improve its viscometric and mucoadhesive properties while maintaining the beneficial properties, which make it useful in ophthalmic applications.</p> <p>N-vinylpyrrolidone is copolymerized with N-vinylformamide to produce a functionalized grafting platform P(VP-co-VF), which is then grafted with low concentrations of short hydrophobic grafts to introduce non-Newtonian flow profile to the precursor.</p> <p>For applications at the back of the eye, the hydrophobic grafted PVP can be injected into the vitreous cavity of the eye in a liquid form to form subsequently a gel-like substance and function as a substitute for the vitreous humour. For application at the front of the eye, the shear thinning properties of hydrophobic-grafted PVP is combined with the mucoadhesive properties of phenylboronic acids (PBA) to improve the bioavailability of the drugs delivered to the front of the eye with eye drops.</p> <p>Rheological characterization of the solutions has shown the potential to form gel-like materials via hydrophobic associations without sacrificing the facile injectability of the material. Targeted gelation and mucoadhesion properties can be obtained by the synthesis of polymers with desired PBA and hydrophobic graft contents.</p> / Master of Applied Science (MASc)