Thesis presented June 27, 2002

Abstract:
The general frame of this thesis is the study of statistical properties of polymer chains at interfaces. This is a theoretical work which aims at linking macroscopic observables (thickness, amount of adsorbed material, surface tension) to the microscopic organization of chains. The polymer layer is described in terms of loops and tails formed by adsorbed polymers, by combining the statistical physics of a loop population of different sizes and scaling laws. First, a formal link is established between this phenomenological approach and first principles of polymer statistical physics, by arguing that this description is a variational theory. Then, this theory is applied to the issue of the surface tension of polymer liquids (semi-dilute solutions and melts). The variations of the surface tension with molecular weight, temperature and volume fraction in the bulk are deduced. A comparison is made with experimental measurements of the surface tension, found in the literature. The involved physical phenomena are then reconsidered. In particular, the role of tensio-activity of chain ends and of the entropy associated to loop distribution are enlightened. This theory is then generalized to describe the adsorption of polyelectrolytes onto an oppositely charged surface in the semi-dilute regime. The layer structure is described analytically and the presence of an external layer made of large loops induces the inversion charge process. Finally, the influence of the concave geometry on the polymer brush structure and the study of mobile polymer connectors are considered. Adhesive properties of such junctions are found to strongly depend on the connected objects geometry and polymer characteristics.

Keywords:
polymer, interface, adsorption, surface tension, polyelectrolyte, scaling laws, polymer brush, mean field, connector, adhesive bridge

On-line thesis. ​