The polymer-silica interaction in elastomeric materials composed of 1,4-cis-polyisoprene rubber and silica was studied by magic angle spinning NMR. The relaxation times in the hydrogen domain are informative about phases at the nanometer scale when a spin propagation phenomenon, due to strong dipolar couplings in the solid, prevails. However, magnetization diffusion is quenched in a rubbery phase where spin-spin relaxation rates are slow. The problem was overcome by promoting spin diffusion below the glass transition at low temperature. The interface was then observed under high-resolution conditions by the reciprocal points of view of 13 C and 29 Si nuclei. In particular, a fast transfer of magnetization from the polymer to the silica surface was observed by cross-polarization dynamics following the nonprotonated silicon atoms. Bidentate coupling agents and vulcanization promote a better interaction with the silica surface. The morphological modifications of the silica particles after processing could also be observed.
An investigation into styrene‐butadiene rubber and styrene‐butadiene rubber/butadiene rubber composites was conducted, aimed at investigating the influence of surface modification of silica on polymer‐filler interactions. Two silanes, bis‐triethoxysilylpropyltetrasulfane and octadecyltriethoxysilane, were used as surface modifiers. A morphological investigation by transmission electron microscopy and automated image analysis provided a quantitative evaluation of the filler distribution in the rubber matrix by using morphometric descriptors, such as projected area, perimeter and area/perimeter ratio. The better dispersion of the surface‐modified silica nicely relates with the improved dynamic‐mechanical and tensile properties and accounts for the higher critical concentration necessary to the formation of the secondary network, thus confirming that the surface modification reduces filler‐filler and enhances polymer‐filler interactions.
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