Polymer nanocomposites are mixtures of nanoparticles and polymer chains, where the filler particles are usually added to enhance mechanical properties, e.g. of car tire materials. Performance depends to a great extent on the structure of the filler, i.e. its dispersion state in the polymer matrix, which itself depends on mixing protocols, but also on the thermodynamics of the system. The latter can be tuned by performing either chemical surface modifications of the nanoparticles, or by playing with the mass and/or grafting properties of the polymer chains. Some straightforward ways to obtain information from small-angle scattering on the filler structure of nanocomposites will be presented. In particular, we recently developed a quantitative analysis of the scattered intensity in the intermediate q range. It is based on the similarity in local structure between infinitely large homogeneous assemblies of hard spheres or moderately sticky hard spheres with any finite-sized nanoparticle assembly dominated by hard sphere interactions. This method provides direct information on the local volume fraction of particles. It will then be applied to the impact of small molecules on the silica structure in nanocomposites close to industrial applications.Finally, a second issue for the mechanical response of nanocomposites relates to the polymer dynamics, which may also be governed by the filler dispersion. We will present first quasi-elastic neutron scattering results showing the impact of the aggregation state on the segmental dynamics of the same samples by means of incoherent neutron spin-echo.

In this talk, some straightforward ways to obtain information from small-angle scattering on the structure of complex systems, in particular nanocomposites, will be given [1]. Polymer nanocomposites are mixtures of nanoparticles and polymer chains, where the particles – called filler – are usually added to enhance mechanical properties, like e.g. in car tires. Performances depend to a great extent on the structure of the filler, i.e. their dispersion state in the polymer matrix, which itself depends on mixing protocols, but also on the thermodynamics of the system. The latter can be tuned by performing either chemical surface modifications of the nanoparticles, or by playing with the mass and/or grafting properties of the polymer chains.We will present recent results on nanocomposites close to industrial applications, including what is probably one of the first quantitative analyses of such disordered structures by a combination of SAXS, TEM and numerical simulations [2]. The study led to the identification of a unique structure-determining parameter [3]. The generalization of the above-mentioned approach – the correlation hole analysis – will furthermore be illustrated by structural studies by small angle scattering of well-defined model systems, showing the influence of chain mass [4] or surface grafting of small molecules [5]. Finally, if the chairman is nice, a quick outlook on why contrast-matching with SANS in nanocomposites often fails will be proposed [6].[1] A.-C. Genix and J. Oberdisse, Structure and dynamics of polymer nanocomposites studied by X-ray and neutron scattering techniques. Current Opinion in Colloid & Interface Science, 2015, 20, 293-303.[2] G. P. Baeza, A. C. Genix, C. Degrandcourt, L. Petitjean, J. Gummel, M. Couty and J. Oberdisse, Macromolecules, 2013, 46, 317-329.[3] G. P. Baeza, A.-C. Genix, C. Degrandcourt, J. Gummel, A. Mujtaba, K. Saalwächter, T. Thurn-Albrecht, M. Couty, and J. Oberdisse, ACS MacroLetters, 2014, 3 (5), 448–452[4] A. Banc, A. C. Genix, M. Chirat, C. Dupas, S. Caillol, M. Sztucki and J. Oberdisse, Macromolecules, 2014, 47, 3219–3230.[5] C. Schmitt Pauly, A.-C. Genix, J. G. Alauzun, M. Sztucki, P. H. Mutin and J. Oberdisse, Polymer, in press.[6] A. Banc, A.-C. Genix, C. Dupas, M. Sztucki, R. Schweins, M.-S. Appavou, J. Oberdisse, Macromolecules 2015, 48, 6596−6605.

A general overview over the physics of soft condensed matter systems, and how to measure their static and dynamic properties with neutron scattering.

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.

Small-angle scattering applied to microemulsions and liquid crystals

Small-angle scattering applied to the sequence of morphologies of self-assembled structures