Lyotropic liquid crystals as self-organizing templates for ordering carbon nanotubes

During the last few years a number of stimulating reports^1-9 have revealed mixtures of carbon nanotubes (CNTs) in liquid crystals (LCs) to be multifaceted and attractive composites with possible applications in diverse areas of science and technology. The meeting between carbon nanotubes—an extreme example of hard functional anisotropic nanoparticles—and liquid crystals—self-organizing anisotropic fluid soft matter—brings up many new intriguing questions of physics and chemistry. So far, the studies have been motivated mainly by a number of interesting observations of potential interest for applications: on the one hand, the LC host transfers its inherent orientational order onto the nanotube guests^1-6, which can be well dispersed in the LC^4-6, on the other, the CNTs can modify the properties of the LC, in some cases improving their performance in e.g. display devices^7-9.

After having given unambiguous proof of the CNT alignment along the LC director in lyotropic^4,6 as well as thermotropic^3,5 LCs using polarized resonant Raman spectroscopy, we are now broadening the scope of our studies of these fascinating composite systems. In addition to monitoring alignment quantitatively and dynamically while modifying the geometry and type of the LC host and / or type and concentration of the CNT guests, we now focus also on the various effects that the CNTs have on the LC, in particular regarding phase sequence, switching dynamics and free ion content. Moreover, we are looking into the interactions between mesogens / surfactants and CNTs on the molecular to the mesoscopic scales, of great importance for understanding the macroscopic behavior of the composite, as well as the interesting and often surprising electrical properties of composites of CNTs and thermotropic LCs.

Uniform dispersion (top left) and uniaxial alignment (top right) of CNTs in lyotropic liquid crystals. The cartoon at the bottom schematically illustrates the alignment concept.

References

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[3] G. Scalia, M. Haluska, U. Dettlaff-Weglikowska, F. Giesselmann, S. Roth, AIP Conf. Proc., 2005, 786, 114
[4] J. P. F. Lagerwall, G. Scalia, M. Haluska, U. Dettlaff-Weglikowska, S. Roth, F. Giesselmann, Adv. Mater., 2006, in press
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[6] J.P.F. Lagerwall, G. Scalia, M. Haluska, U. Dettlaff-Weglikowska, S. Roth, and F. Giesselmann, Phys. Stat. Sol. B, 243, 2006, 3046
[7] (a) H.-Y. Chen, W. Lee, Appl. Phys. Lett., 2006, 88, 222105
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|9] C.-Y. Huang, C.-Y Hu, H.-C. Pan, K.-Y. Lo, Jap. J. Appl. Phys., 2005, 44, 8077