Macroscopic-scale carbon nanotube alignment via self-assembly in lyotropic liquid crystals

Abstract

a b s t r a c tBy dispersing carbon nanotubes (CNTs) in a lyotropic liquid crystalline matrix, uniaxial alignment of the nanotubes can easily be achieved over macroscopic areas. We briefly describe the principles behind the technique and then show that it can be applied to multiwall as well as single-wall nanotubes and that a variety of different dispersing materials can be used, from industrial surfactants to DNA. We also present a new microfluidics-based method for transferring the liquid crystal-dispersed CNTs to a substrate, maintaining a fair control of tube direction.

A new era for liquid crystal research: Applications of liquid crystals in soft matter nano-, bio- and microtechnology

“…The first successful way of drastically raising the nanotube concentration was to switch to lyotropic liquid crystal hosts, where the option to use surfactants for stabilizing the nanotube dispersion allowed a much greater concentration of the nanoparticle guests [78,83,88,89] Particularly high nanotube loading was possible by using two different ionic surfactants of opposite charge, one for dispersing the nanotubes and the other for building the liquid crystal phase. In this way Scalia et al succeeded in reaching such high nanotube loading at such good alignment that the composite behaved like a liquid linear polarizer [90,91], cf. Fig.…”

Filament formation in carbon nanotube-doped lyotropic liquid crystals

“…While this insensitivity to CNT type may at first seem somewhat surprising, it is in fact reasonable since the anisometry even of MWCNTs is exceptional. They are also aligned by the liquid crystal along the director 8 and they can thus also be expected to have the required stiffening effect on the micelles and form chains parallel to n. In contrast, spherical C 60 fullerenes will not stiffen the micelles, even if they are expected to build linear chains due to anisotropic depletion attraction, 22,23 hence they cannot induce the filament formation.…”

“…It may for instance be beneficial to use tailor-designed tips for the extraction, such as tapered tungsten wires. 9 For achieving arbitrarily long filaments one could pump the CNT/LC phase to the drawing well using a microfluidic set-up, 8 allowing continuous replenishment of the source fluid.…”

“…CNTs that are well dispersed in a liquid crystal (LC) spontaneously align along the director n, the preferred orientation of the host phase [2][3][4][5][6] . We recently demonstrated that an efficient approach is to incorporate CNTs dispersed with the anionic surfactant sodium dodecylbenzenesulfonate (SDBS) in an aqueous lyotropic LC phase formed by the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) 7,8 . With this combination liquid crystalline dispersions of single-as well as multiwall nanotubes can be prepared at sufficiently high concentration, with large-scale uniform alignment, that the composite fluid acts as a linear polariser, cf.…”

Phase Separations in Mixtures of a Nanoparticle and a Liquid Crystal

“…Indeed thermotropic (Basu & Iannacchione, 2008;Dierking et.al., 2005;Jayalakshmi & Prasad, 2009;Lynch & Patrick, 2002;Russell et.al., 2006) as well as lyotropic nematic liquid crystals (Courty et.al., 2003;Lagerwall et. al., 2007;Schymura et. al., 2009;Weiss et.…”