The characterization of polymer nanocomposites on molecular length scales and timescales is a challenging task, which is also indispensable for the understanding of macroscopic material's properties. Neutron scattering is one of the techniques which are very well-suited for studying the structure and molecular motion in such soft matter systems. X-rays can also be used for the same purpose, however, with higher energy and thus a different focus on dynamics, where they are better suited for nanoparticle motion. In this mini-review, we aim at highlighting recent results in the field of polymer nanocomposites, including nanoparticle structure in various experimental systems, from model to industrial, and polymer and particle dynamics. This allows establishing the link between microscopic and macroscopic properties, in particular rheology.

Depuis des années, les déchets collectés lors d’expéditions menées en mer sont triés, comptés etcaractérisés pour quantifier l’ampleur de la pollution plastique. Si la prise de conscience de la pollutionplastique était initialement liée à l'omniprésence des macro-déchets, il est désormais clair que lapollution la plus problématique est "invisible", c'est-à-dire due à des débris de plus petite taille (microet nano-plastiques) provenant de la dégradation des macro-déchets. Néanmoins , la quantité totale, ladistribution en taille des déchets plastiques dans les différents compartiments environnementaux,ainsi que leur évolution temporelle sont toujours source de questionnement. Dans l’état actuel desconnaissances, les données de terrain sur la distribution en taille des particules de plastique collectéesà la surface des océans présentent les caractéristiques suivantes. En parcourant les tailles de la plusgrande à la plus petite, un premier pic d'abondance est observé autour de 1 mm. Entre 1 mm etenviron 150 μm, on trouve très peu de particules. L'abondance augmente à nouveau de 150 μm à 10μm, avec une quantité de particules de plusieurs ordres de grandeur supérieure à celle trouvée autourde 1 mm.Dans cette présentation, nous proposerons une nouvelle approche théorique de la fragmentation d’undéchet, permettant de simuler l’évolution temporelle de l'abondance et la distribution desmicroplastiques. Nous examinerons l’influence du mode de collecte et discuterons de la pertinencedes résultats obtenus en regard des données expérimentales

Thanks to their giant nonlinear optical response, liquid crystals support the existence of spatial optical solitons called nematicons. These solitons can be experimentally imaged in a microscope thanks to the fluctuation-induced scattering of the laser beam, but the associated microscope images are generally hard to interpret due to the partially incoherent nature of light scattering. In this contribution, we introduce a theoretical framework allowing to simulate microscope images originating from bulk scattering sources. We apply this framework to the visualization of laser beams and bouncing solitons in the weak nonlinear regime, and show that our framework could be the basis for a novel tomography technique of optical fields.

This work focuses on the temperature-dependent structural and rheological characterization of polystyrene-b-poly(n-butyl acrylate)-b-polystyrene triblock copolymers (PS-b-PnBA-b-PS) in the melt and, in particular, on their ability to show a lower disorder-to-order temperature (LDOT). To this aim, copolymers of varying block lengths, but keeping the PnBA block as a major component, were synthesized. Smallangle x-ray scattering revealed that the copolymers with short PS blocks (∼10 kg/mol) approach an LDOT but do not cross it. At room temperature, these copolymers exhibit higher moduli compared to a PnBA homopolymer due to the reinforcing effect of the PS but are flowing at temperatures above the glass transition of the PS. Increasing the PS and PnBA block length, to keep the same PS fraction, induces more profound changes in the structural and viscoelastic behaviors. Such a copolymer crosses the LDOT, leading to a microphase-separated and ordered state at high temperature. Contrary to the copolymers with short PS blocks, the flow regime was not reached, even at temperatures well above the glass transition of the PS. Instead, a low-frequency plateau was observed in rheology, showing the increased lifetime of the microphase-separated PS domains. ABA triblock copolymers exhibiting an LDOT behavior could, thus, be of interest for the design of thermoplastic elastomers or pressure-sensitive adhesives that can resist the flow at high temperatures