Elaboration of transparent composite materials based on hybrid core@shell nanoparticles

L’incorporation de particules inorganiques dans une matrice polymère confère de nouvelles propriétés au matériau ou améliore de manière significative les propriétés déjà existantes. Cependant, l’apparence visuelle perçue, telle que la transparence, peut être altérée par des phénomènes de diffusion de la lumière par les particules. Cette diffusion de la lumière est principalement conditionnée par la dimension des particules –ou agrégats de particules- et la différence d’indice de réfraction entre la matrice et les charges. Afin de traiter ces deux problèmes, l’objectif de nos travaux était de contrôler simultanément l’état de dispersion des nanoparticules inorganiques dans la matrice polymère et l’indice de réfraction des nanoparticules de façon à l’ajuster à celui de la matrice. Pour élaborer ce nouveau composite, nous avons synthétisé des nanoparticules hybrides cœur@écorce avec un cœur inorganique qui apporte les nouvelles propriétés et une écorce polymère d’épaisseur contrôlée, obtenue par polymérisation radicalaire contrôlée par voie nitroxyde amorcée à la surface des nanoparticules inorganiques. L’écorce polymère limite l’agrégation des particules et permet de modifier l’indice de réfraction moyen des nanoparticules cœur@écorce. En contrôlant l’épaisseur et la nature chimique de l’écorce polymère, nous cherchons à ajuster l’indice de réfraction des nanoparticules cœur@écorce à celui de la matrice. Les nanoparticules ont ensuite été dispersées dans une matrice de poly(méthacrylate de méthyle). Les propriétés optiques des composites ont été caractérisées par spectrogoniophotométrie, afin d’obtenir des informations sur l’intensité et la distribution angulaire de la lumière transmise par le composite. La transparence des nanocomposites a été fortement améliorée en ajustant l’indice de réfraction des nanoparticules cœur@écorce à celui de la matrice.The incorporation of inorganic particles into a polymer matrix confers new properties to the material or enhances significantly existing properties. However, the perceived visual appearance, such as loss of transparency, might be modified by the scattering of light by the particles. This light scattering is mainly due to the particle –or aggregates of particles- dimensions and the refractive index difference between matrix and fillers. In order to address both issues, the objective of the present work was to control simultaneously the dispersion state of the inorganic nanoparticles into the polymeric matrix and the refractive index of the nanoparticles to match the one of the matrix. To achieve this new composite, we designed hybrid core@shell nanoparticles with an inorganic core that brings new properties and a polymer shell of controlled thickness, obtained by surface-initiated nitroxide mediated controlled radical polymerization. The polymer shell limits the aggregation of the particles and enables us to tune the average refractive index of the hybrid core@shell particle. By controlling the thickness and the chemical nature of the polymeric shell, we targeted to match the refractive index of the hybrid core@shell particle to the one of the polymeric matrix. The nanoparticles were further dispersed into a poly(methyl methacrylate) matrix. Optical properties of composites were characterized by spectrogoniophotometry which gave us informations about the intensity and the angular distribution of the transmitted light by the nanocomposites. The transparency of the nanocomposites was strongly enhanced for core@shell particles fulfilling the refractive index matching conditions

Transparent polymer nanocomposites: An overview on their synthesis and advanced properties

International audienceSince the last decade, there has been an increasing demand for the design of more advanced functional materials. The integration of inorganic nanoparticles to polymer matrices is a powerful tool to confer their fascinating and complementary properties to the polymer materials. Among the different polymer nanocompos-ites, transparent nanocomposites are of particular interest due to their significance in a wide range of applications. To achieve a high level of transparency in the nanocomposites, it is necessary to minimize the aggre-gation of the nanoparticles that induce significant light scattering and thus hamper the application for transparent materials. The basic concepts of light scattering, the refractive index modulation and the methods to characterize the transparency of nanocomposites are provided to introduce this review. The fabrication of the transparent nanocomposites has been the subject of many efforts to develop methods to limit aggregation. To address this challenge, several methods have been implemented to control the polymerization process, the nanoparticle synthesis, and the polymer-nanoparticle interface together with the polymer casting or processing. The main methodologies developed to fabricate transparent nanocomposites are discussed according to four main categories: the blending of nanoparticles and polymer; the in-situ polymerization in the presence of pre-formed nanoparticles; the in-situ nanoparticle synthesis in a pre-formed polymer matrix; and finally the simultaneous polymerization and in-situ nanoparticle synthesis. The few studies dealing with casting of polymer solution loaded with core-shell nanoparticles are also discussed. In light of the literature on polymer nanocomposites, this review focuses on transparent nanocomposites with special attention given to the level of transparency and how this transparency is assessed for each study claiming transparency of the nanocom-posite. For each class of nanocomposites, it is of great importance to provide an overview of the different level of transparency according to the thickness of the polymer material. The second part of the review provides a thorough overview of the properties investigated in transparent nanocomposites with attention paid to the characterization of transparency. The transparent nanocomposites were described according to the targeted properties which are primarily the improvement of mechanical properties, thermal stability, barrier properties, magnetic properties and the optical properties. The optical properties have been the most thoroughly investigated due to the myriad inorganic nanoparticles exhibiting an excellent wide range of optical properties. Thus, the present review also describes the polymer/nanoparticle systems designed for the fabrication of transparent polymer nanocomposites with advanced optical properties: UV or IR-filtering properties, photoluminescence, ability to produce extreme refractive index, dichroism or non-linear optical properties

3D-printing of nano-polysaccharide/collagen composite bio-ink

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Improved 3D-printability of collagen with nano-polysaccharides

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Dual vaccination against IL-4 and IL-13 protects against chronic allergic asthma in mice

International audienceAllergic asthma is characterized by elevated levels of IgE antibodies, type 2 cytokines such as interleukin-4 (IL-4) and IL-13, airway hyperresponsiveness (AHR), mucus hypersecretion and eosinophilia. Approved therapeutic monoclonal antibodies targeting IgE or IL-4/IL-13 reduce asthma symptoms but require costly lifelong administrations. Here, we develop conjugate vaccines against mouse IL-4 and IL-13, and demonstrate their prophylactic and therapeutic efficacy in reducing IgE levels, AHR, eosinophilia and mucus production in mouse models of asthma analyzed up to 15 weeks after initial vaccination. More importantly, we also test similar vaccines specific for human IL-4/IL-13 in mice expressing human IL-4/IL-13 and the related receptor, IL-4Rα, to find efficient neutralization of both cytokines and reduced IgE levels for at least 11 weeks post-vaccination. Our results imply that dual IL-4/IL-13 vaccination may represent a cost-effective, long-term therapeutic strategy for the treatment of allergic asthma as demonstrated in mouse models, although additional studies are warranted to assess its safety and feasibility