Thesis presented June 10, 2002
Abstract:
This thesis proposes a phenomenological approach for "hairy" membranes, those bilayers with macromolecules grafted to it. Hairy membranes are biomimetic systems and help to understand the coupling between curvature of a membrane and the bidimensionnal organization of the macromolecules on it. In a first part, we underscore the forces due to polymer chains that tend to bend the membrane. An important feature is the fluidity of the membrane. This property allows the polymer to adapt to curvature: a local deformation creates a long-range reorganization of the chains. Furthermore, a preliminary study shows that the coexistence of the hairy membrane with a reservoir of polymer in solution does not modify qualitatively these results. The second part is devoted to a unique macromolecule multiply anchored to the membrane. This macromolecule is considered as a polymer chain in good solvent, grafted by anchors regularly set along the chain. We describe the different phases such a molecule can adopt, and the constraints the various conformations exert on the membrane. The main result is that the effects of the polymer dominate the spontaneous curvature for standard chains. Therefore, the polymer becomes a manageable control parameter of the surface state.
Keywords:
polymer, membrane, biophysical curvature, statistical physics, phase coexistence
On-line thesis.