Surface-Driven Switching of Liquid Crystals Using Redox-Active Groups on Electrodes
Yan-Yeung Luk and
Nicholas L. Abbott*
Electrochemical control of the oxidation state of ferrocene-decorated
electrodes leads to surface-driven changes in the orientations
of thermotropic liquid crystals. When the electrodes possess
nanometer-scale topography, voltages of 0.0 to 0.3 volts (versus
a counter electrode in a two-electrode cell) can drive changes
in the orientation of the liquid crystals in the plane and/or
out of the plane of the electrodes. Electrodes not supporting
ferrocene do not lead to surface-driven orientational transitions.
The in-plane transitions are driven by the reorganization of
the monolayer of ferrocene upon oxidation of ferrocene to ferrocenium.
The out-of-plane transition reflects a dielectric coupling between
the liquid crystal and the diffuse part of an electrical double
layer that evolves upon oxidation of ferrocene to ferrocenium.
These results suggest new ways to couple the orientations of
liquid crystals to chemical and electrical stimuli in electro-optical
devices and chemical sensors.
* To whom correspondence should be addressed. E-mail: abbott{at}engr.wisc.edu
