Binary c–T phase diagrams of organogelators in solvent are frequently simplified to two domains, gel and sol, even when the melting temperatures display two distinct regimes, an increase with T and a plateau. Herein, the c–T phase diagram of an organogelator in solvent is elucidated by rheology, DSC, optical microscopy, and transmitted light intensity measurements. We evidence a miscibility gap between the organogelator and the solvent above a threshold concentration, cL. In this domain the melting or the formation of the gel becomes a monotectic transformation, which explains why the corresponding temperatures are nonvariant above cL. As shown by further studies by variable temperature FTIR and NMR, different types of H-bonds drive both the liquid–liquid phase separation and the gelation.

Wet acid oxidation treatment methods have been widely reported as an effective method to purify and oxidize the surface of industrial multi-walled carbon nanotubes (MWCNT). This work examines the use of a concentrated HNO3/H2SO4 mixture in an attempt to optimize the purification procedure of industrial MWCNT with diameter distribution statistics. It is shown that acid treatments of several hours are enough to purify the nanotubes. The electrical and thermal conductivities of epoxy composites containing 0.05-0.25 wt. % of acid-treated MWCNT has been studied. The electrical conductivity of the composites decreases by more than three orders, whereas the thermal conductivity of the same specimen increases very modestly as a function of the filler content.

Photo-active pi-conjugated molecules (quaterthiophene and phthalocyanine) are either encapsulated into the hollow core of single-walled carbon nanotubes or non-covalently stacked at their outer surface in order to elaborate hybrid nano-systems with new physical properties, providing practical routes to fit different requirements for potential applications. In this study, we are interested in the relationship between the structure and the opto-electronic properties. The structural properties are investigated mainly by x-ray diffraction and/or Transmission Electron Microscopy and Raman spectroscopy. We evidence that the supramolecular organizations of confined quaterthiophenes depend on the nanocontainer size whereas phthalocyanine encapsulation leads the formation of a 1D-phase for which the angle between the molecule ring and the nanotube axis is close to 32°. Confined phthalocyanine molecules display Raman spectra hardly altered with respect to the bulk phase, suggesting a rather weak interaction with the tubes. In contrast, the vibrational properties of the molecules stacked at the outer surface of tubes display important modifications. We assume a significant curvature of the phthalocyanine induced by the interaction with the tube walls and a change of the central atom position within the molecular ring, in good agreement with our DFT calculations.

In this theoretical work, we study the polarized infrared spectra of double-walled carbon nanotubes (DCNTs) as a function of their diameters, chiralities and lengths. For infinite DCNTs, mathematical relations are derived to estimate the diameter of the inner and outer tubes from the knowledge of their experimental mid-infrared spectra. The infrared spectra of DCNTs with a finite length are also calculated using the spectral moments method. We observe additional infrared bands as a function of the relative lengths of the inner and outer tubes. Bands located below 900 cm-1 give reliable information about these lengths.

In this work, we develop the concept of evaporation-induced self-structuring as a novel approach forproducing organised films by exploiting cooperative physical and chemical interactions under far-fromequilibriumconditions (spin-coating), using sol–gel precursors with multiple functional groups. Thin filmsof self-structured silsesquioxane nanohybrids have been deposited by spin coating through the sol–gelhydrolysis and condensation of a bridged organosilane bearing self-assembling urea groups. The resultingnanostructure, investigated by FTIR, AFM and SEM, is shown to be highly dependent on the catalyst used(nucleophilic or acidic), and can be further modulated by varying the spinning rate. FTIR studies revealed thepresence of highly organised structures under acidic catalysis due to strong hydrogen bonding between ureagroups and hydrophobic interactions between long alkylene chains. The preferential orientation of the ureacross-links parallel to the substrate is shown using polarized FTIR experiments.