Mark A. Hamon

DISSOLUTION OF SINGLE-WALLED CARBON NANOTUBES

834 Ó WILEY-VCH Verlag GmbH, D-69469 Weinheim, 1999 0935-9648/99/1007-0834

Solution-phase EPR studies of single-walled carbon nanotubes

17.50+.50/0 Adv. Mater. 1999, 11, No. 10 be detected. Furthermore, the mechanical properties of the complex are solid-like at temperatures below the observable glass transition, which would not be the case for a phase separated material containing rubbery microdomains. Instead, we advance an explanation for the extraordinary properties of this liquid crystal complex by invoking a high degree of coupling between mesogenic side groups and the ethylene oxide backbone which thereby inhibits the formation of helical conformations favored by afreeo poly(ethylene oxide) chains. Within such helical arrangements the lithium ions would be tightly coordinated below Tg and effectively trapped. By suppressing the formation of such helical structures, an open ethylene oxide structure is obtained within which lithium ions are free to move and where empty sites exist for the ions to occupy. It is remarkable that a similar (but weaker) effect is observed in the amorphous material. It seems that insertion of rigid isophthalate units also inhibits helical formation, sufficient to provide a measure of ionic decoupling, but for the liquid crystal complex the open structure is further stabilized via the interactions between the liquid crystal side groups. It is worth noting that this view is supported by the continuity of behavior from the melt into the glassy state in both the heat capacity and electrical conductivity, indicating that the structure of the melt is not strongly influenced by temperature. In addition, the dissolution of the ions in the backbone does not swell the smectic layer and thus, the open network must be relatively unchanged at least in the direction normal to the smectic layers. This suggests that by careful engineering of the types of liquid crystal phase present, it should be possible to tailor the conductivity mechanism to particular applications. It is also remarkable that the conductivity in the MeOC6G6 complex increases strongly (by several orders of magnitude) as the AO:Li ratio is decreased from 10:1 to 3:1. We should now be able to employ more concentrated polymer electrolytes than is presently possible with conventional materials. Transport number data for these electrolytes are not yet available, but it is tempting to speculate that the elimination of acation trappingo within the ethylene oxide helix will lead to substantial increases in cation mobility. For many years this has been one of the principal goals of polymer electrolyte research.

Reactivity, spectroscopy, and structure of reduced fullerenes

Abstract We report EPR studies on pristine, purified, shortened and soluble SWNTs in various solution phases. Some of these samples give rise to strong, sharp EPR signals, and this technique is useful for monitoring the presence of SWNTs in aqueous and organic solvents. The soluble SWNTs carry about 1 unpaired electron per 10000 carbon atoms and give a free electron g-value.

Solution Properties of Single-Walled Carbon Nanotubes

Abstract Reduced fullerenes, the simplest covalent derivatives of the fullerene family of carbon allotropes, provide an excellent context for the study of the fundamental chemical reactivity of fullerenes. We have developed a general method for the formation of a number of these compounds. Using Zn(Cu) reduction, we have access to pure samples of several isomerically pure C 60 H n and C 70 H n species. We have completely assigned the 13 C NMR spectrum of C 60 H 6 and have assigned the majority of the resonances in C 60 H 2 .