One-dimensional crystals of 25% C-13-enriched C-60 encapsulated inside highly magnetically purified SWNTs were investigated by following the temperature dependence of the C-13 NMR line shapes and the relaxation rates from 300 K down to 5 K. High-resolution MAS techniques reveal that 32% of the encapsulated molecules, so-called the C-60(alpha), are blocked at room temperature and 68%, labeled C-60(beta), are shown to reversly undergo molecular reorlentational dynamics. Contrary to previous NMR studies, spin - lattice relaxation time reveals a phase transition at 100 K associated with the changes in the nature of the C-60(beta) dynamics. Above the transition, the C-60(beta) exhibits continuous rotational diffusion; below the transition, C-60(beta) executes uniaxial hindered rotations most likely along the nanotubes axis and freeze out below 25 K. The associated activation energies of these two dynamical regimes are measured to be 6 times lower than in fcc-C-60, suggesting a quiet smooth orientational dependence of the interaction between C-60(beta) molecules and the inner surface of the nanotubes.

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We present a route to synthesize polyacetylene filled multi-walled carbon nanotubes (MCNT) by in situ polymerization. We use supercritical carbon dioxide to fill the nanotubes with toluene and then add the Ziegler-Natta catalyst. In order to assure controlled polymerization inside the nanotube, the catalyst outside is removed before the reaction. The resulting polyacetylene filled nanotubes are characterized by H-1 NMR and scanning electron microscope. (c) 2005 Elsevier B.V. All rights reserved.

We describe a novel purification process for single-wall carbon nanotube (SWNT) materials that removes non-nanotube carbon and reduces ferromagnetic impurities to levels at which native SWNT magnetic properties predominate. Ferromagnetism is reduced from 1.04 to less than 0.013 emu/g by magnetic gradient filtration. This procedure creates samples of sufficient quality for spectroscopies such as nuclear magnetic resonance (NMR). The overall cleanliness and purity of the material is confirmed through NIR absorption spectroscopy, X-ray diffraction, C-60 filling experiments with yields exceeding 90%, and high-resolution C-13 NMR.

Supercritical carbon dioxide is an universal tool to impregnate carbon nanotubes with a wide range of organic molecules. In this Letter, we present our results of carbon nanotubes filled with the photo-conducting polymer poly(N-vinyl carbazole) and the conducting polymer polypyrrole which were prepared by polymerizing the monomers inside the nanotubes. The endohedral nanotubes were characterized by HRTEM and H-1 NMR which confirmed that the encapsulated material was indeed the conducting polymer. (c) 2006 Elsevier B.V. All rights reserved.

We report on orientational order and dynamics of a nematic liquid crystal confined in porous silica. 13C NMR lineshape is used as a fingerprint for this study. A procedure based on exchange of non-coupled sites is implemented in order to obtain the corresponding local order parameter S and the characteristic time for molecular reorientation . Our results evidence that in the nematic phase, S decreases when confinement increases. By means of Langevin dynamics simulations of confined liquid crystals, we show that this behavior is due to topological defects, originated by the absorbed-layers phenomenon as a consequence of the strong anchoring of these molecules on silica surfaces.