Résumé
Nanocomposites made of hard inorganic nanoparticles (NPs) embedded in a soft polymer matrix may have rheological properties of interest for various applications, and in particular car tires. These properties depend crucially on the dispersion of the filler NPs, which has been studied in simplified industrial (i.e., without crosslinker and related chemistry) styrene–butadiene nanocomposites with silica filler NPs. We have developed a quantitative structural analysis based on a combination of electron microscopy, Monte Carlo simulations, and small-angle X-ray scattering. It allowed us to establish a global structural model, where primary silica beads are organized within small aggregates, which themselves fill large-scale fractal branches. Experimental parameters have been varied independently, starting with the silica volume fraction si, the matrix composition (percentage of graftable chains), and the chain mass. The grafting density on the silica NPs was shown to be the structure- and rheology-determining parameter, and we will show that a simple mechanism is able to explain the evolution of aggregate size and mass with grafting density. Moreover, dynamical properties have been followed by broadband dielectric spectroscopy (BDS) recently, and the detailed characterization of two high-temperature silica-related processes provided evidence that one of them can be linked to the structural evolution of these nanocomposites. Our work thus suggests that such high-temperature BDS-measurements can be used to detect reorganizations in structurally complex silica nanocomposites.Baeza et al, Macromolecules 2013, ibid 2013, ACS Macro Letters 2014, Soft Matter 2014