Unusually structure-selective growth of single-walled carbon nanotubes (SWNTs) has been attained using a CVD method with a solid supported catalyst. In this method, CO feedstock disproportionates on silica-supported catalytic nanoclusters of Co that are formed in situ from mixed salts of Co and Mo. The nanotube products are analyzed by spectrofluorimetry to reveal distributions resolved at the level of individual (n,m) structures. Two structures, (6,5) and (7,5), together dominate the semiconducting nanotube distribution and comprise more than one-half of that population. The average diameter of produced SWNTs is only 0.81 nm, and a strong propensity is found favoring chiral angles near the armchair limit.

Nonisothermal and isothermal crystallization experiments were performed on polypropylene mixed with carbon nanotubes produced by disproportionation of CO on Co−Mo catalysts. Functionalization of the nanotubes with octadecylamine made the tubes hydrophobic and allowed the tubes to be solubilized in an organic solvent. Mixing of the nanotubes with the polymer was accomplished by adding the nanotubes to a Decalin solution that contained dissolved polypropylene, followed by evaporation of the solvent. Dynamic mechanical analysis indicated very little difference in the small-strain mechanical properties between filled and unfilled polymers at the very low solid levels that were tested. By contrast, the crystallization behavior of the filled and unfilled polymer was quite different. Nanotubes promoted growth of the less-preferred beta form of crystalline polypropylene at the expense of the alpha form. In nonisothermal crystallization, the total amount of crystalline material in the sample was the same for the filled and unfilled materials. However, for isothermal crystallization experiments, the percent crystallinity in the filled materials was slightly higher. Most importantly, the rate of crystallization was substantially higher in the filled system. The results presented in this paper clearly show that carbon nanotubes nucleate crystallinity in polypropylene.

Water solubilization of single-walled carbon nanotubes (SWNTs) has been achieved by functionalizing the SWNT with glucosamine. The grafting of glucosamine to the nanotubes was attained by producing acyl chloride on the carboxylic groups associated with the nanotubes. Subsequently, amide bonds were formed between the glucosamine and the SWNT. This grafting results in solubility of SWNT in water, which ranges from 0.1 to 0.3 mg/mL, depending on temperature.

The disproportionation of CO over Co-Mo/SiO 2 catalysts with low Co/Mo ratios results in a high selectivity to single-walled carbon nanotubes (SWNTs) when the reaction is conducted between 700 and 950 °C in a flow of pure CO at a total pressure between 1 and 5 atm. A detailed characterization involving Raman spectroscopy, temperature-programmed oxidation (TPO), and transmission electron microscopy (TEM) shows that the product of this process has a high concentration of SWNTs. Depending on the temperature of operation, the selectivity and nanotube diameter can be varied.

SWNT-filled polystyrene (SWNT-PS) and styrene−isoprene (SWNT-SI) composites prepared by miniemulsion polymerization showed distinctive physical features such as uniform black coloration, high solubility in toluene as well as in tetrahydrofuran (THF), and semiconductor to ohmic electrical behavior. Raman spectra for both hybrid materials suggested a reduced vibrational freedom of the polymer chains as a consequence of the nanotube incorporation. An adsorbed polymer layer on the nanotube bundles contributes to a better dispersion of the inorganic nanoreinforcement.

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