Disorder in condensed matter systems can profoundly affect dynamic and thermodynamic behavior, creating novel material properties and unique challenges for statistical mechanics. As part of our effort to investigate problems in disordered and

1
CAREER Structure and Dynamics of Disordered and
Out-of-Equilibrium Systems, pg. 1 Robert L.
Leheny, Johns Hopkins University, DMR-0134377
(A)
Disorder in condensed matter systems can
profoundly affect dynamic and thermodynamic
behavior, creating novel material properties and
unique challenges for statistical mechanics. As
part of our effort to investigate problems in
disordered and out-of-equilibrium systems, we
have been studying liquid crystals confined in
random environments formed by anisotropic porous
media. One example is liquid crystal/colloidal
gel nanocomposites, illustrated in Figs. A and B.
In these materials the anisotropic gel structure
selects an orientation for the liquid crystal
molecules but impedes their translational order.
This experimental realization of such a novel
random environment has permitted detailed tests
of emerging theoretical ideas. Due to the
strongly anisotropic optical properties of liquid
crystals, their unusual behavior under
confinement in these compliant gels also leads to
new material properties that could have potential
application in optical devices.
Figure A Measurement of capacitor containing
liquid crystal. Due to coupling of liquid
crystal order to electric fields, the value
depends on applied voltage. The effect is
reversible for a pure material (blue) but
irreversible for a liquid crystal/gel
nanocomposite (red) as the gel restructures.
(B)
70 Å
Figure B Schematic of a liquid crystal/gel
nanocomposite. The anisotropic gel structure
results from elastic coupling to liquid crystal,
which has been aligned by an external electric
or magnetic field. The anisotropic structure
persists after the field is removed.
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CAREER Structure and Dynamics of Disordered and
Out-of-Equilibrium Systems, pg. 2 Robert L.
Leheny, Johns Hopkins University, DMR-0134377
(C)
Recent x-ray scattering experiments have
characterized the microstructure of these
nanocomposite materials. Figures C and D
illustrate results from these measurements. The
x-ray image in Fig. C provides a quantitative
measure of the degree of anisotropy in the
material. High-resolution measurements of the
scattering intensity, shown in Fig. D, provide
information about the spatial correlations among
liquid crystal molecules that can test recent
theoretical predictions for the behavior of
liquid crystals in such anisotropic random
environments.
Figure C X-ray image of the scattering intensity
from a smectic liquid crystal within an
isotropic colloidal gel. The strongly peaked
intensity near pixels (200,200) and (1000,200)
indicates that the orientation of the liquid
crystal is macroscopically aligned by its
interactions with the gel.
Educational and outreach opportunities made
possible through this award (1) Graduate
research projects for three students working
toward a Physics Ph.D. (Clayton Lapointe, Dennis
Liang, and Hasan Yardimci). (2) Summer research
experience for an undergraduate physics major
(Andrew OBannan). (3) Participation in research
for a high school intern in coordination with the
Ingenuity Project of Baltimore (Clifton Mobbs).
(D)
Figure D High resolution measurement of the
x-ray scattering intensity associated with
smectic ordering in a liquid crystal in an
anisotropic gel.