(Invited) The Impact of Carbon Nanotube Length and Diameter on Their Global Alignment by Dead-End Filtration

Abstract

Dead-end filtration on polyvinylpyrrolidone-coated polycarbonate track-etched membranes has proven to be an effective method to prepare macroscopically (3.8 cm²) aligned thin films from solution-based single-wall carbon nanotubes (SWCNTs). However, to make this technique broadly applicable, the role of SWCNT length and diameter on the alignment process must be understood. To date, most groups report the alignment of unsorted large diameter (» 1.4 nm) SWCNTs, but systematic studies on their small diameter (» 0.78 nm) counterparts are rare and in the case of sorted SWCNT species, non-existent. In this work, films are prepared from two series of length sorted fractions comprised of small and large diameter SWCNTs, respectively. The degree of alignment is characterized by cross polarized microscopy, scanning electron microscopy and Raman spectroscopy. For the longest fractions, the two-dimensional order parameter, , values of » 0.66 and » 0.76 are reported for the small and large diameter SWCNTs, respectively, and Raman maps over an area of 2500 μm2 are presented. A comparison of Derjaguin, Landau, Verwey and Overbeek (DLVO) theory calculations with the aligned domain size is then used to propose a law identifying the required length of a carbon nanotube with a given diameter and zeta potential for alignment.