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This paper presents an efficient way to measure the curing kinetics and gel point, αgel, in epoxy resins from one single experiment. The epoxy curing reaction is herein monitored using in situ and time-resolved near-infrared absorption spectroscopy (NIR). The curing profiles over different isothermal conditions are in good agreement with DSC. Furthermore, the increase of the NIR absorption bands of aromatic rings (unreactive throughout curing) probe the cure shrinkage, as more and more aromatic rings are localized within the fixed sample volume. Therefore, the gel point is determined using the onset of the aromatic absorption increase. The results are in good agreement with the theoretical gel point, as well as DMA results. This innovative approach enables gelation measurements on epoxy neat resins and film composites with an easy-to-perform, accurate, robust, and versatile method.

To date, aqueous stable graphene flakes solutionscan be obtained by simple REDOX reactions.1–5 Most of the current applications regardinggraphene require ordered nanostructuredcomposites materials. Liquid crystal phases orderingrepresent an opportunity to arrange theminto macroscopic assemblies with long-rangeordering. 1,2 Preparing organized materials andthin films from these dispersions then requires agood control of the liquid crystal ordering duringthe deposition and the drying of the films. As amatter of fact, it turns out that graphene flakeseasily align at high shear.3,4 On the other hand,Graphene Flakes Liquid Crystals (GFLC) exhibita very interesting behaviour at low shear or undersmall displacements, thin films often showspeculiar patterns (such as the periodic texturesshown in Fig.72-72). We have shown how tocreate and stabilize large-sized periodic texturesin GFLC. The patterns have been characterizedunder optical and electronic microscopies. Theirstability can be explained by the competition betweenthe anchoring field of the substrate andthe presence of a yield stress resulting fromthe peculiar elastic and rheological properties ofthe GFLC. Our findings also clarify why longstandinghypotheses on the presence of exoticphases1 at large concentrations are present inthe literature.
References[1] Zakri, C.; Blanc, C.; Grelet, E.; Zamora-Ledezma, C.; Puech, N.; Anglaret, E.; Poulin, P. Philosophical Transactions of theRoyal Society A: Mathematical, Physical and Engineering Sciences 2013, 371, 20120499..
[2] Zamora-Ledezma, C.; Puech, N.; Zakri, C.; Grelet, E.; Moulton, S. E.; Wallace, G. G.; Gambhir, S.; Blanc, C.; Anglaret, E.;Poulin, P. The journal of physical chemistry letters 2012, 3, 2425–2430..
[3] Poulin, P.; Jalili, R.; Neri, W.; Nallet, F.; Divoux, T.; Colin, A.; Aboutalebi, S. H.; Wallace, G.; Zakri, C. Proceedings of theNational Academy of Sciences 2016, 113, 11088–11093..
[4] Zamora-Ledezma, C.; Jeridi, H.; Anglaret, E.; Blanc, C. Orientations and periodic textures in graphene liquid crystals. 27thInternational Liquid Crystal Conference (ILCC2018). 2018..
[5] Xu, Z.; Gao, C. Nature communications 2011, 2, 571.

Nowadays, the recovering of both thicknesses and optical properties of nanometric multilayers is still a challenge. We propose a method to recover the effective relative permittivities and the thicknesses of copper/copper oxide layers, from absorbance spectra measured in the visible spectra. The experimental data are fitted with a model of classical light-matter interaction and a combination of two Drude-Lorentz laws to calculate the relative permittivities over the spectrum. The Particle Swarm Optimization and the evolutionary methods are used for the least-square fitting. A two steps study reveals that the relative permittivities of bulk cannot be used to fit adequately the absorbance curves. However, a perturbation of these reference values improves their fitting. The method is applied to the absorption spectra of a set of three copper samples that are progressively oxidized by six successive heat treatments.