Preparation and Characterization of a Carbon Nanotube−Lyotropic Liquid Crystal Composite

Abstract

We present a detailed study on the integration of individual single-walled carbon nanotubes (SWNTs) within a lyotropic hexagonal liquid crystal (LC) for the first time. Two systems are studied in this work; in the first, the same surfactant is used for both the dispersion of the SWNTs and the formation of the LC. In the second system, we use different surfactants for the dispersion of SWNTs and LC formation. Light microscopy imaging combined with small-angle X-ray scattering (SAXS) indicates that the nanotubes (NTs) are well dispersed and aligned along the LC director. The macroscopic property, namely, the viscosity, is strongly enhanced by the presence of the NTs.

Carbon nanotubes in liquid crystals

“…In particular, a switch to DNA or another polyelectrolytic surfactant for dispersing the CNTs should render the system more robust. A hexagonal columnar lyotropic host phase was also used as host for SWCNTs by Weiss et al 51 and for MWCNTs by 5 Jiang et al 55 . While the latter team worked with a nonionic polyoxyethylene surfactant and an ionic liquid solvent for dispersing the CNTs as well as for forming the LC phase, the former worked with water-based systems, using the anionic surfactant Triton X-100 for forming the LC host phase and the 10 CNTs were dispersed either in Triton X-100 or in SDS.…”

Carbon Nanotubes in Liquid Crystals

“…This situation is largely due to the fact that standard surfactants used for preparing high-quality CNT dispersions are perfect as the basis for making lyotropic LC-CNT composites. In contrast to the case of thermotropic LC- 45 CNT composites, one thus always starts by preparing an isotropic low-surfactant-concentration suspension of CNTs, and then this is made liquid crystalline by adding more surfactant [24][25][26] or it is added to an already prepared lyotropic liquid crystal sample 51,55 . Adding dry CNT powder directly to 50 a preformed lyotropic liquid crystal phase works poorly 55 , as it is difficult to break up the large CNT aggregates of a dry CNT sample in such a viscous host.…”

“…While this depletion attraction limits the amount of CNTs that can be suspended, as well as the 70 maximum concentration of surfactant, its exact role in liquid crystalline systems is somewhat unclear, as all modelling of depletion phenomena that we know of has been done for the case of spherical micelles forming an isotropic phase. The fact that lyotropic LC phases have been successfully loaded with 75 CNTs [24][25][26]51 at a surfactant content well beyond the limit where an isotropic aqueous CNT-surfactant system was reported to suffer strongly from depletion attraction 49 suggests that the special conditions of the LC phase has considerable impact on the phenomenon. In particular, one 80 must probably take the impact of long-range orientational order of elongated micelles (both with and without nanotubes) on the total excluded volume into account.…”

“…A hexagonal columnar lyotropic host phase was also used as host for SWCNTs by Weiss et al 51 and for MWCNTs by 5 Jiang et al 55 . While the latter team worked with a nonionic polyoxyethylene surfactant and an ionic liquid solvent for dispersing the CNTs as well as for forming the LC phase, the former worked with water-based systems, using the anionic surfactant Triton X-100 for forming the LC host phase and the 10 CNTs were dispersed either in Triton X-100 or in SDS.…”

Phase Separations in Mixtures of a Nanoparticle and a Liquid Crystal

“…al., 2007;Schymura et. al., 2009;Weiss et. al., 2006) have been applied as nematic solvents for the alignment of nanotubes.…”