Revealing the Substructure of Single-Walled Carbon Nanotube Fibers

Abstract

Single-walled carbon nanotubes (SWNTs) uniquely combine characteristics of polymers (e.g., they are molecules composed of repeat units) as well as nanoscale colloids (e.g., they are extremely stiff); because of these characteristics, they may qualify as the ideal building blocks for the long-sought Staudinger's “continuous crystal.” To this end, neat SWNT fibers have been produced by wet-spinning concentrated dispersions of 6−10 wt % SWNTs in 102% H2SO4. A unique protocol that combined UV−ozone dry chemical etching and cryoultramicrotoming was developed to directly visualize the internal voids, alignment, and composition of these SWNT neat fibers. A substructure of large aligned SWNT ropes, 200−500 nm in diameter, was revealed throughout the fibers. This substructure may be linked to the SWNT spaghetti, threadlike liquid-crystalline domains observed in dispersions of SWNTs in H2SO4.