Résumé:

The question of the typical structure of nano-objects (nanoparticles, aggregates, fibers, discs, chains, ….) is recurrent in our research, and small-angle scattering of neutrons and X-rays are prominent techniques to answer it. The first part of this presentation will be devoted to a (hopefully) didactical introduction to scattering: how the technique works in practice, and what one can get out of it. In the second part, a few applications in polymer nanocomposites will be discussed. Rubber-based nanocomposites prepared by solid-phase mixing with precipitated silica nanoparticles are typically strongly aggregated systems with different levels of spatial organization, as highlighted by our group in the past [1,2]. The strategy that we developed was to investigate such systems based on the study of simplified industrial samples with ingredients limited to a strict minimum. The analysis of small-angle X-ray scattering data can then be performed on the scale of a micrometric simulation box. Tens of thousands of “model” nanoparticles are embedded in the matrix, and their dispersion strongly affects both the mechanical properties of the material, and the scattered intensity. A statistical method based on a reverse Monte Carlo solution of this many-parameter scattering problem will be presented, showing that some key features like percolation can be described [3]. Another key feature of rubber nanocomposites refers to the influence of the filler surfaces on the polymer structure and dynamics, and some recent progress will be highlighted [4]. In particular, we have studied blends of short and long chains, where one chain type is deuterated, by small-angle neutron scattering. Different degrees of spatial segregation could be identified recently, including a peculiar, “fish-shaped” interfacial gradient characterized also by reverse Monte Carlo simulations, this time of the interface. References [1] Guilhem P. Baeza, Anne-Caroline Genix, C. Degrandcourt, Laurent Petitjean, Jérémie Gummel, Marc Couty, Julian Oberdisse, Macromolecules 2013, 46, 317−329 (cover article) [2] A.C. Genix and J. Oberdisse, Current Opinion in Colloid and Interface Science, 2015, 20 (4), 293-303 [3] Musino D, Genix A-C, Chauveau E, Bizien T, Oberdisse J, Nanoscale 2020, 12:3907. [4] A.C. Genix, V. Bocharova, B. Carroll, P. Dieudonné-George, M. Sztucki, R. Schweins, A. P. Sokolov, and J. Oberdisse, ACS Applied Materials and Interfaces, 2021, 11 (19), 17863-17872