Interplay between Polymer Chain Conformation and Nanoparticles Assembly in Model Industrial Silica/Rubber Nanocomposites
Résumé
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 and
experiments on well-defined model PNC. Here we present the first experimental study about the
influence of NP on the polymer chain conformation for PNC designed to be as close as possible to
industrial 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 interfacial
coating or coupling additives usually employed in the manufacturing mixing process. We associated
specific chain (d) labeling, and the so-called Zero Average Contrast (ZAC) method, with SANS, in-situ
SANS and SAXS/TEM experiments to extract the polymer chain scattering signal at rest for non-cross
linked and under stretching for cross-linked PNCs. NP loading, individual clusters or connected
network, as well as the influence of the type, the quantity of interfacial agent and the influence of the
elongation rate have been evaluated on the chain conformation and on its related deformation. We
clearly distinguish the situations where the silica is perfectly matched from the unperfected matching by
direct comparison of SANS and SAXS structure factor. Whatever the silica matching situation, the
additive type and quantity and the filler content, there is no thus significant change in the polymer
dimension for NP loading up to 15% v/v within a range of 5%. One can see an extra scattering
contribution at low Q, as often encountered, enhanced for non-perfect silica matching but also visible
for perfect filler matching. This contribution can be qualitatively attributed to specific h or d chains
adsorption onto the NP surface inside the NP cluster that modifying the average scattering neutron
contrast of the silica cluster. Under elongation, NP act as additional cross-linking junction preventing
chain relaxation giving a deformation of the chain with NP closer to theoretical phantom network
prediction than for pure matrix.
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