Since 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 nanocomposites, 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 aggregation 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 Abbreviations: Ag, silver; Al 2 O 3 , alumina; APTMS, (3-Aminopropyl)trimethoxysilane; ATO, antimony-doped tin oxide; Au, gold; CaCO 3 , calcium carbonate; CaF 2 , calcium fluoride; CdS

International audienceThe first purpose of this paper is to underline a relevant colorimetric co-ordinate characterizing the colour of ochres within their extremely wide range, from pale yellow to dark red. The second purpose is to link together quantitatively the variations of this colorimetric co-ordinate and the various chemical compositions of the samples, mainly hematite, goethite and white pigments. A group of 30 modern ochres and a group of 20 ancient ochres have been investigated. All these natural pigments have been commercialized. Diffuse reflectance spectrometry allows to calculate the colorimetric co-ordinates in the CIE-L*a*b* space and the position of the absorption band of each sample. Physico-chemical analysis has been obtained by quantitative X-ray diffraction, scanning and transmitting electronic microscopy and particle-size analysis by laser diffraction. The positive a* co-ordinate (redness) has been underlined, for the first time, to be the only relevant colorimetric parameter to characterize the colour of the ochres. Its variations are quantitatively connected to the shift of the absorption band due to the charge transfer between the ligand (OH− or O2−) and the Fe3+ ion contained in goethite and/or hematite. For ochres containing both hematite and goethite, the a* co-ordinate linearly increases with the relative amount of hematite while the absorption band progressively shifts towards the high wavelengths. Such a linear shift of the absorption band has never been underlined before. For ochres containing only one iron oxide, a* linearly decreases with the amount of white pigments, whatever the nature of the white charges. Moreover, this study gives the opportunity to show that only the nature, the amount and the size distribution of the white charges allow to discriminate the ochres according to their geographic origin

The aim of this work was to develop a bioresorbable, biodegradable and biocompatible synthetic polymer with good mechanical properties for bone tissue engineering applications. Polylactic acid (PLA) scaffolds were generated by 3D printing using the fused deposition modelling method, and reinforced by incorporation of graphene oxide (GO). Morphological analysis by scanning electron microscopy indicated that the scaffold average pore size was between 400 and 500 μm. Topography imaging revealed a rougher surface upon GO incorporation (Sa = 5.8 μm for PLA scaffolds, and of 9.9 μm for PLA scaffolds with 0.2% GO), and contact angle measurements showed a transition from a hydrophobic surface (pure PLA scaffolds) to a hydrophilic surface after GO incorporation. PLA thermomechanical properties were enhanced by GO incorporation, as shown by the 70 °C increase of the degradation peak (thermal gravimetric analysis). However, GO incorporation did not change significantly the melting point assessed by differential scanning calorimetry. Physicochemical analyses by X-ray diffraction and Raman spectroscopy confirmed the filler presence. Tensile testing demonstrated that the mechanical properties were improved upon GO incorporation (30% increase of the Young's modulus with 0.3%GO). Cell viability, attachment, proliferation and differentiation assays using MG-63 osteosarcoma cells showed that PLA/ GO scaffolds were biocompatible and that they promoted cell proliferation and mineralization more efficiently than pure PLA scaffolds. In conclusion, this new 3D printed nanocomposite is a promising scaffold with adequate mechanical properties and cytocompatibility which may allow bone formation.

A novel route to obtain highly ordered self-assembled honeycomb films has been investigated by a bottom-up process. A polymer with one chain end ionic functionality has been synthesized in a one-step reaction by nitroxide-mediated polymerization. This ionomer synthesis represents a very simple way, and honeycomb structured films have been observed after solvent evaporation in a long-range distance of few hundred microns in a very regular ordered arrangement. These films are simply prepared by spreading out polymers CS 2 solutions without additives over various substrates as well on inorganic surfaces as onto different polymeric substrates such as flexible PVC sheet or rigid PMMA plate. Different experimental parameters, such as polymer concentration or wet thickness, have been checked to tune the pores size and thus the honeycomb morphologies. An elegant technique based on reflected and transmitted light has been used to correlate the pores size inside and on the top of the film. This highly ordered hexagonal pattern on the polymeric surfaces suggests the possibility of taking advantage of the microtextures for inducing optical interferences but also to modify the color of this bioinspired material as a function of their visual angle as in nature.