Interplay between Polymer Chain Conformation and Nanoparticles Assembly in Model Industrial Silica/Rubber Nanocomposites

The question of the influence of nanoparticles (NP) on chain dimensions in polymer nanocomposites(PNC) has been treated mainly through the fundamental way using theoretical or simulation tools andexperiments on well-defined model PNC. Here we present the first experimental study about theinfluence of NP on the polymer chain conformation for PNC designed to be as close as possible toindustrial systems employed in tire industry. PNC are silica nanoparticles dispersed into a Styrene-Butadiene-Rubber (SBR) matrix whose NP dispersion can be managed by NP loading with interfacialcoating or coupling additives usually employed in the manufacturing mixing process. We associatedspecific chain (d) labeling, and the so-called Zero Average Contrast (ZAC) method, with SANS, in-situSANS and SAXS/TEM experiments to extract the polymer chain scattering signal at rest for non-crosslinked and under stretching for cross-linked PNCs. NP loading, individual clusters or connectednetwork, as well as the influence of the type, the quantity of interfacial agent and the influence of theelongation rate have been evaluated on the chain conformation and on its related deformation. Weclearly distinguish the situations where the silica is perfectly matched from the unperfected matching bydirect comparison of SANS and SAXS structure factor. Whatever the silica matching situation, theadditive type and quantity and the filler content, there is no thus significant change in the polymerdimension for NP loading up to 15% v/v within a range of 5%. One can see an extra scatteringcontribution at low Q, as often encountered, enhanced for non-perfect silica matching but also visiblefor perfect filler matching. This contribution can be qualitatively attributed to specific h or d chainsadsorption onto the NP surface inside the NP cluster that modifying the average scattering neutroncontrast of the silica cluster. Under elongation, NP act as additional cross-linking junction preventingchain relaxation giving a deformation of the chain with NP closer to theoretical phantom networkprediction than for pure matrix.