Extensive Study of Clay-Polymer Composites: Elaboration, Characterization, Exact Adsorption Theory

Résumé

The research work of this thesis is dedicated to an extended experimental and theoretical study of natural clay-polymer composites. Firstly, we theoretically reexamined the problem of determining the architecture of adsorption isotherms for clay-polymer composites using Renormalization Theory we constructed. The latter provided us exact scaling relations, close to the polymer adsorption temperature, which describe the architecture of adsorption isotherms. In fact, these isotherms we determined experimentally, express the evolution of the amount adsorbed at equilibrium, as a function of the polymer concentration, at fixed molar mass and temperature. Then, this theory was tested experimentally, and it was observed that it is in good quantitative agreement with experiment. Secondly, we conducted an experimental and theoretical study of the basal distance and diffraction peak characteristics (peak heights, peak positions, peak intensities, crystallite sizes), as a function of the polymer concentration, at fixed molar mass and temperature, for a natural bentonite-poly(ethylene glycol) composite we elaborated. The natural bentonite was extracted from a deposit located in the eastern Rif mountain chain of Morocco (near Nador city). The basal distance and diffraction peaks characteristics were measured by X-Ray Diffraction (XRD). Then, we developed a theoretical approach based on an introtroduced Renormalization Theory, and obtained exact scaling relations for the physical quantities of interest, which are found to be consistent with our experimental data. Finally, using Fourier Transform Infrared Spectroscopy (FTIR), we studied and discussed the important influence of the polymer concentration on vibration, stretching and bending modes. Thirdly, we were concerned with a derivation of an exact scaling relationship between the basal distance and the amount of adsorbed polymer of any clay-polymer composite. For this purpose, we made use of an elaborated geometric scaling theory. Then, we compared our theoretical predictions with experimental data obtained by XRD. This comparison showed that theory and experiment are in good quantitative agreement. Finally, our fourth objective was the study of a local bentonite-poly(ethylene glycol) composite. More precisely, the goal was to examine the effect of the molecular weight of poly(ethylene glycol) on the basal distance, the amount adsorbed polymer and position and intensity of XRD peaks. On the theoretical level, we established an exact scaling relationships between these physical quantities and the molecular weight of polymer, making use of the geometric scaling theory mentioned above. It was observed that the comparison between our theoretical predictions and our experimental data is very satisfactory.

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