Impact of graphene incorporation on the orientational order of graphene/liquid crystal composites

2H NMR spectroscopy was used to characterize changes in the liquid crystal (LC) phase behavior and orientational order resulting from the dispersion of graphene nanoplatelets within the nematic 4-cyano-4′-n-pentyl-biphenyl (5CB) liquid crystal. The graphene/5CB composites revealed a decreased isotropic to nematic phase transition temperature (TIN) and a reduction in LC orientational order, with increasing graphene volume fraction. In contrast, the graphene/benzene/5CB composites revealed both an increased TIN and an increase in the LC orientational order with graphene addition. These changes result from anisotropic surface interactions between the graphene nanoplatelets and LC, and are discussed in terms of the mean-field theory for nanoparticle doped LCs.