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π-π Stacking Molecular Interactions Between Carbon Nanotubes and 5CB Liquid Crystal

Published online by Cambridge University Press:  28 March 2011

Georgi Y. Georgiev ,
Erin A. Gombos ,
Michael B. McIntyre  and
Peggy Cebe
Georgi Y. Georgiev
Affiliation:
Department of Natural Sciences, Assumption College, Worcester, MA 01609, U.S.A. Department of Physics and Astronomy, Tufts University, Medford, MA 02155, U.S.A.
Erin A. Gombos
Affiliation:
Department of Natural Sciences, Assumption College, Worcester, MA 01609, U.S.A.
Michael B. McIntyre
Affiliation:
Department of Natural Sciences, Assumption College, Worcester, MA 01609, U.S.A.
Peggy Cebe
Affiliation:
Department of Physics and Astronomy, Tufts University, Medford, MA 02155, U.S.A.
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Abstract

Multiwall Carbon Nanotubes (MWCNT) align by coupling to the liquid crystals’ (LC) nematic director in LC/MWCNT dispersions. This coupling is so strong that the LC molecules act as molecular motors to reorient the MWCNTs when an electric field is applied across oriented electro optic cells. On the other hand, MWCNTs also improve the LC order and modify the crystal phase of LCs. We investigate the physical reasons for those strong effects by studying the molecular interactions between a host LC and MWCNTs. It has been predicted theoretically that the aromatic rings could stack with their π orbitals in 4-Cyano-4’-pentylbiphenyl (5CB) and MWCNT nanocomposites. Experimentally 5CB modifies the MWCNTs Raman breathing modes in the same nanocomposites. In turn, we look for evidence of this interaction between MWCNTs and LCs at the 5CB molecules. Using FTIR spectroscopy we found that the modes corresponding to 5CB aromatic rings vibrations are affected in the presence of MWCNTs which confirms that π-π stacking of 5CB’s biphenyl rigid core to the carbon rings on the MWCNTs’ surface may indeed be major mechanism for MWCNT/LC nematic coupling. It shows also that the Raman breathing mode effects on MWCNTs can be due to this π-π stacking interaction with 5CB. Further investigations of the MWCNTs interactions with 5CB can lead to developing of a complete model of this phenomenon and help applications for electro optic cells, nanoswitches, new crystal forms for optics, communication technology and others.

Keywords

liquid crystalinfrared (IR) spectroscopynanoscale
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1293: Symposium L – Liquid-Crystal Materials—Beyond Displays , 2011 , mrsf10-1293-l09-07
Copyright
Copyright © Materials Research Society 2011

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References

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