Exfoliation of graphene oxide and its application in improving the electro-optical response of ferroelectric liquid crystal

Abstract

Near complete exfoliation and reduction of lyophilized graphene oxide (GO) has been carried out at temperature as low as 400 °C. The structural characterizations of the reduced GO have been performed using X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy techniques. The morphological studies were carried out using scanning electron microscopy. The synthesized GO finds an application in improving the switching performance of a liquid crystal (LC) mixture by remarkably modifying the physical properties, such as spontaneous polarization and rotational viscosity of the ferroelectric LC (FLC) material which in turn resulted into faster response of the FLC. The present study explores the possibility of low temperature thermal reduction of GO along with its application in improving the properties of LC based display systems.

Nanostructured Electrospun Hybrid Graphene/Polyacrylonitrile Yarns

“…Considering the DSC thermograms of the twisted yarns, a clear increase in stabilization temperature and a corresponding decrease in Δ H could be realized with inclusion of LCGO [ 41 , 42 ]. The increase in the stabilization temperature of PAN/LCGO fibers upon the addition of LCGO content as well as the decrease in the Δ H could be due to the intermolecular interactions between PAN and LCGO, particularly when being heat treated during thermal analysis.…”

Recent progress and future perspectives on carbon-nanomaterial-dispersed liquid crystal composites

“…the aggregation of CNMs [102,113,[120][121][122]. In some studies, either the vortex mixing or strong homogenization (at speeds up to 35 000 rpm) and/or ultrasonication of the predispersion has been carried out for a time period ranging up to a few hours to ensure the uniform dispersion of CNMs in solvents.…”

“…A small concentration (0.04 wt.%) of the graphene nanoflakes (0.55-3.74 nm) was dispersed in a FLC matrix using a vortex homogenizer followed by 5 h of ultrasonication to achieve a uniform dispersion [102]. The effect of different concentrations of exfoliated GO nanoflakes on the alignment of FLC material (W301) was analyzed and 0.1 wt.% concentration was found to be the limiting value to be added into the FLC matrix without remarkably perturbing the alignment [120]. However, the presence of small GO aggregates was observed in the form of light leakage regions in the dark states of the composites (figure 11).…”

“…However, the phenomenon of trapping of ionic charges by CNMs such as GO could not be generalized. It was found in some reports that the presence of impurity ions and high polarizability of functional groups, such as −COOH, −OH, etc, attached with GO could cause increased magnitudes of ϵ ′ as well as tan δ especially in the low-frequency regime [120].…”

“…the elastic constants. In most of the studies, the presence of CNMs caused a remarkable decrease in the magnitude of η of the host FLC mixture to result in a faster response of the composites [102,104,111,114,120,135]. The investigation on the graphene-flake-dispersed FLC composite revealed that the suspended graphene flakes could enhance the effective value of P S by improving smectic-C ordering due to the π-π electron stacking, and reduced rotation viscosity by trapping some of the free ions of the FLC media [102].…”