Structures et propriétés rhéologiques d’auto-assemblages de copolymères amphiphiles cationiques en peigne

摘要

Comb-like amphiphilic copolyelectrolytes (polysoap) based on styrene (hydrophobic unit) and N,N dimethylalkyl(vinylbenzyl)ammonium chloride (surfactant-like unit) have been studied. In aqueous solution, the comonomer ratio influences the morphology of the self-assemblies displayed by these polymers. For a composition of 80 %mol of the surfactant-like unit, the micelles have a cylindrical shape; such topology displays interesting rheological properties at the macroscopic scale. The main goal of this thesis has consisted in characterizing the rheological and structural properties of these self-assembly, in order to correlate them with the chemical structure of the polysoaps.The structural study, with scattering techniques (Light and Neutron) and Cryo-microscopy, have shown that the cylindrical micelles grow in length with increasing polymer concentration and display some hydrophobic defects at their interface which induce their connection leading to the formation of a network. Addition of salt screens cationic charges, increases the density of junction, and leads to a phase separation.Branched cylindrical micelles networks display viscoelastic behaviors, with a narrow distribution of relaxation times. Break-up of the micelles and of the junctions accounts for the origin of the relaxation. Increasing the length of the alkyl side chain affects as well as adding a neutral surfactant affects deeply the relaxation time of the gels.