Graphene oxide (GO) nanoparticles of two different sizes are dispersed inthe nematic liquid crystal (LC) 5CB covering a wide concentration range. Thedielectric properties, as well as the electrooptic behavior, including thresholdvoltage, elastic constant, and response times are investigated as a functionof GO concentration. It is found that small graphene oxide flakes of meansize of 560 nm are better and easier dispersible than larger flakes of 2.8 μmmean size. The nematic–isotropic transition only increases slightly for the(GO+LC) hybrid systems. For increasing GO concentrations the thresholdvoltage and splay elastic constant dramatically increase, until saturation fora concentration of ≈1% by weight GO. The field driven switching-on time ispractically independent of concentration, while the switching-off time, whichis purely elastically driven, exhibits a strongly decreasing behavior. Dielectricspectroscopy reveals a noncollective relaxation which is absent in the neatliquid crystal. This may be attributed to a drastically slowed down molecularrelaxation related to the rotation around the short axis of the liquid crystalmolecules. When heating the thermotropic liquid crystal into its isotropicphase, the latter acts as a solvent for the GO particles, and a lyotropicnematic phase with largely reduced birefringence is formed.
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