Résumé:

Model systems of nanocomposites are important for our understanding of the structural and dynamical contributions of the constituents to macroscopic properties, and in particular mechanical reinforcement. Systems in which the filler aggregation can be finely tuned thanks to an aqueous casting route were developed1. The control of the initial colloidal solution stability (mixture of nanolatex and colloidal silica) by the pH enabled to obtain various microstructures for given silica fractions. Using Small Angle Neutron Scattering (SANS) and Transmission Electronic Microscopy (TEM) data, aggregation diagrams were obtained and enabled to study separately the effect of the silica fraction and its aggregation state on mechanical properties2 (see left side of the figure). On the other hand, we studied polymer structure and dynamic in such nanocomposites. SANS experiments were performed on samples prepared with a mixture of hydrogenated (H) and deuterated (D) chains in order to match the silica signal and get independently the polymer signal. A first system made with incompatible H and D latex beads enabled to follow the demixing kinetic for various silica fractions. The evolution of H zone size with annealing indicated that the polymer was immobilized in 15% v silica samples (see right side of the figure)2. A second system made with compatible beads highlighted the dissolution kinetic of latex beads with annealing. With sufficient annealing conditions a molecular mixture of H and D chains was obtained and the effect of silica fraction on chain radius of gyration was studied.