Résumé
Small-angle scattering of neutrons (SANS) or x-rays (SAXS) are powerful experimental methods giving insight in the structure on the nanoscale of typical soft matter systems, like colloids or polymers, in solution or in bulk. In the first part of this lecture, the basic concepts of small angle scattering will be introduced and applied to the structural determination of popular nanostructures, like nanoparticle (NP) sizes, characterization of NP assemblies, including fractal aggregates, as well as polymer chain conformations. Usually, they are all investigated as single component in binary systems, like NPs suspended in a solvent. In the second part, a few examples in the field of polymer nanocomposites will be discussed, see ref. [1] for a review. The formation of aggregates may be tuned by different physico-chemical parameters, like those governing electrostatic interactions, surface modifications of NPs, or chain grafting, with direct consequences on the mechanical reinforcement of such materials [2]. In this context, both model nanocomposites [3] and samples close to industrial applications [4,5] like car tires will be studied. Chain configurations in complex systems like nanocomposites can be studied by SANS experiments. This requires the formulation of ternary systems made of deuterated and hydrogenated polymer, plus the filler NPs, and is possible using zero-average contrast conditions or similar [6]. Finally, a recently proposed model explaining the repeated (and expensive!) failures – including our own – will be discussed [7]. [1] Genix AC, Oberdisse J, Structure and dynamics of polymer nanocomposites studied by X-ray and neutron scattering techniques, Current Opinion in Colloid and Interface Science, 2015, 20 (4), 293-303.[2] Oberdisse J, Soft Matter 2006, 2 (1), 29-36.[3] Banc A, Genix AC, Chirat M et al. Tuning structure and rheology of silica-latex nanocomposites with the molecular weight of matrix chains: a coupled SAXS-TEM-simulation approach. Macromolecules 2014; 47:3219–3230.[4] Baeza GP, Genix AC, Degrandcourt C et al. Multiscale Filler Structure in Simplified Industrial Nanocomposite Silica/SBR Systems Studied by SAXS and TEM. Macromolecules 2013; 46:317-329[5] Baeza GP, Genix AC, Degrandcourt C et al. Mechanism of aggregate formation in simplified industrial silica styrene-butadiene nanocomposites: effect of chain mass and grafting on rheology and structure. Soft Matter 2014; 10:6686–6695.[6] Genix AC, Tatou M, Imaz A et al. Modeling of Intermediate Structures and Chain Conformation in Silica−Latex Nanocomposites Observed by SANS During Annealing. Macromolecules 2012; 45:1663–1675.[7] Banc A, Genix AC, Dupas C et al. On the origin of small-angle scattering from contrast-matched nanoparticles: A study of chain and filler structure in polymer nanocomposites. Macromolecules 2015; 2015, 48, 6596−6605.