Résumé
Polymer nanocomposites are used widely, mainly for the industrial application of car tyres. The rheological behavior of such nanocomposites depends in a crucial way on thedispersion of the hard filler particles – typically silica nanoparticles embedded in a soft polymer matrix. It is thus important to assess the filler structure, which may be quitedifficult for aggregates of nanoparticles of high polydispersity, and with strong interactions at high loading. This has been achieved recently using a coupled TEM/SAXSstructural model describing the filler microstructure of simplified industrial nanocomposites with grafted or ungrafted silica of high structural disorder. Here, wepresent an original method capable of reducing inter-aggregate interactions by swelling of nanocomposites, diluting the filler to low-volume fractions. Note that this isimpossible to reach by solid mixing due to the large differences in viscoelasticity between the composite and the pure polymer. By combining matrix crosslinking,swelling in a good monomer solvent, and post-polymerization of these monomers, it isshown that it is possible to separate the filler into small aggregates. The latter have then been characterized by electron microscopy and small-angle X-ray scattering,confirming the conclusions of the above mentioned TEM-SAXS structural model applied directly to the highly loaded cases.