Carbon-based nanomaterials have emerged as a subject of enormous scientific attention due to their outstanding mechanical, electrical and thermal properties. Incorporated in a polymeric matrix, they are expected to significantly improve physical properties of the host medium at extremely small filler content. In this work, we report a characterization of various carbonaceous materials by Raman spectroscopy that has become a key technique for the analysis of different types of sp 2 nanostructures, including one-dimensional carbon nanotubes, two-dimensional graphene and the effect of disorder in their structures. The dispersion behavior of the D and G' Raman bands, that is, their shift to higher frequencies with increasing laser excitation energy, is used to assess the interfacial properties between the filler and the surrounding polymer in the composites.

The Raman spectra of (1 − x)(BMITFSI), xLiTFSI ionic liquids, where 1-butyl-3-methylimidazolium cation (BMI + ) and bis(trifluoromethane-sulfonyl)imide anion (TFSI − ) are analyzed for LiTFSI mole fractions x < 0.4. As expected from previous studies on similar TFSI-based systems, most lithium ions are shown to be coordinated within [Li(TFSI) 2 ] − anionic clusters. The variation of the self-diffusion coefficients of the 1 H, 19 F, and 7 Li nuclei, measured by pulsed-gradient spin-echo NMR (PGSE-NMR) as a function of x, can be rationalized in terms of the weighted contribution of BMI + cations, TFSI − 'free' anions, and [Li(TFSI) 2 ] − anionic clusters. This implies a negative transference number for lithium.

In-depth confocal Raman microspectrometry (CRM) studies through a planar interface between materials of mismatched refraction indices are known to be affected by a decrease in both collected Raman intensity and axial resolution as a function of focal depth. A complete treatment of these phenomena would require diffraction and refraction effects to be taken into account. Baldwin and Batchelder have recently modeled the refraction effects by considering the influence of the dimensions of the confocal pinhole aperture on the collection efficiency. Their theoretical predictions are compared here with experimental results obtained for a standard 200 µm thick polyethylene (PE) sample. It is shown that the decrease in Raman intensity as a function of focal depth is weaker than predicted, suggesting that off-axis refraction effects cannot be neglected. We therefore propose a simple two-parameter relation which reproduces the observed Raman intensities down to 150-200 µm focal depths. Other in-depth experiments on various test samples, a silicon wafer buried in Nujol oil, PE films of different thicknesses and a polycarbonate slab, were then performed in order to show how the Raman intensity decrease, the radial resolution and the axial interfacial broadening can be directly estimated as a function of the focal depth position. Also, CRM experiments were carried out on a four-layer polymer laminate in order to find the best optical conditions. 'Edge' analyses remain the most efficient way to investigate polymer interfaces but, when in-depth analyses are needed, we tried to evaluate to what extent interfacial broadenings impede the investigation of interpenetration effects at buried interfaces. It is demonstrated that the refraction effects sharpen the interfacial broadenings and the apparent axial resolution does not drastically deteriorate with increasing depth. Indeed, when focused 120 µm deep into a non-absorbing sample, the interface is found to be broadened by a factor of only 7.5 or 3.7 using a 100× or a 50× objective lens; the axial resolution then takes a reasonable value of about 13 µm.

Raman micro-spectroscopy is used to analyse the plastic behaviour of window glass (a soda-lime silicate glass) under high hydrostatic pressure and Vickers indentation. We show pressure-induced irreversible structural changes, notably an increase of Q(2) species at the expense of Q(3). For the first time, a very accurate [Formula: see text] calibration curve has been established. Local density variations of a Vickers indented window glass have been characterized by micro-Raman mapping using a high spatial resolution device. The effects of glass depolymerization on indentation and hydrostatic compression are discussed. Differences between window glass and pure SiO(2) glass behaviour under high stresses are also highlighted and analysed at a local scale.

The reinforcement of a styrene‐butadiene rubber (SBR) by single fillers—carbon black (CB) or multiwall carbon nanotubes (MWNTs)—or by mixtures of CB and MWNTs, is investigated. The morphologies, mechanical and electrical properties of the composites, are analyzed. A significant improvement in the tensile properties is observed for samples containing a dual phase. Using atomic force (AFM) and transmission electron (TEM) microscopies, we demonstrate that the double loading improves the dispersion of the nanotubes in SBR. Electrical measurements show lower resistivity and a lower percolation threshhold for composites containing blends of fillers, which provides further evidence of better dispersion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 46: 1939–1951, 2008

Gas clathrate hydrates or gas hydrates are made of H-bonded water molecules forming cages, within which gaseous (guest) molecules are encapsulated. The formed clathrate structures, which may be metastable, depend on the nature and on the partitioning of the guest molecules in the water cage. This work focuses on the structural and vibrational properties of nitrogen hydrate in its two clathrate forms (namely, SI and SII) in the thermodynamic ranges 50−200 bar and 150−270 K, together with a comprehensive analysis of the transformation from SI to SII of this gas hydrate. The thermal expansion of both structures has been measured at 1 bar, and the melting of the nitrogen hydrate has been measured at ca. 210 K at 1 bar. Moreover, the SI structure is metastable in the studied pressure region: from time-dependent neutron powder diffraction analysis, it is shown that the SI structure transforms over time to the SII structure with a rate of (1.37 ± 0.17) × 10 5 s −1 at 100 K and at 1 bar. The transformation is also characterized by an induction time (i.e., the lifetime of the pure SI structure) of 0.49 day. We have also investigated the guest partitioning of the nitrogen hydrate using highresolution Raman scattering. Vibrational bands of nitrogen molecules encapsulated in large cages are measured at lower wavenumbers than the one associated with encapsulation in small cages (by 1.1 cm −1 in SI and 0.8 cm −1 in SII). In the case of the thermodynamically stable SII phase, the dependence of the guest partitioning has been characterized as a function of the pressure−temperature conditions. Variation of the relative cage filling is demonstrated. While the small cages remain singly occupied according to previous neutron diffraction analysis, this variation is attributed to large cages of the nitrogen hydrate that easily catch or release nitrogen guest molecules. This study thus provides new opportunities for preparing nitrogen gas hydrates with a "targeted" structure and relative cage filling not only by varying the pressure and temperature but also by playing with the structural metastability.

A symmetric lithium cell Li/P(EO)0 LiTFSI/Li has been studied at 80°C by confocal Raman microspectrometry while current densities of up to 0.5 mA cm are passed through the cell. The Raman observation is performed on the edge of the cell along a line of points extending from one electrode to the other at a depth of about 20 tm within the electrolyte. Local salt concentration is measured in the electrolyte as a function of time, current density I, and electrolyte thickness L (90 and 160 tm). When the steady-state regime is reached, linear and symmetric salt concentration gradients are observed. They are proportional to I and L as expected from the theoretical predictions for a binary electrolyte containing a fully dissociated salt with negligible ionic associations. In addition, preliminary results have been obtained concerning the establishment and relaxation of the steady state. From these data, it is shown that salt diffusion coefficient and ionic transport numbers can be determined with a reasonable precision. Confocal Raman microspectrometry can therefore be considered as a new and powerful spectroelectrochemical method to study transport properties in polymer electrolytes.

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