Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Abstract: S1.00195 : Carbon nanotubes effects on the order parameter and crystal structure of 5CB liquid crystal
Author:
Carbon nanotubes (CNTs) are elongated anisotropic molecular size
cylinders
that can form a liquid crystal (LC) phase in lyotropic solutions.
When
dispersed in LCs their nematic directors couple. We have observed
a large
downshift in transition voltage during Freedericksz transition in
LC/CNT
nanocomposites. We are interested in the effect that CNTs have on
the order
parameter of LCs and their phase diagram and crystal structure.
We measured
using polarized UV/Vis absorption spectra a systematic increase
of the order
parameter of LC/CNT cells with increase of the CNTs content. The
order
parameter vs temperature slope decreases with increased CNTs
content, which
shows that CNTs support an increased order of the LCs to higher
temperatures. This makes the Nematic-to-Isotropic transition sharper
increasing its first order phase transition characteristics. The
main
mechanism for the strong nematic coupling is pi-pi stacking
between the
aromatic rings of the CNTs and LCs which we measure using FTIR
and Raman
difference spectroscopy. Through Polarized Microscopy,
Ellipsometry and DSC
we observed a change in crystalline order and an increase in
nematic to
crystal phase transition temperature with increasing CNTs
concentration due
to their crystal nucleation activity.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.S1.195
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