Size-Dependent Liquid Crystal Behavior of Graphene Oxides for Preparation of Highly Ordered Graphene-Based Films

Abstract

Featured Application Graphene films with both excellent mechanical and electrical properties is considered as promising materials for multi-functional electronic devices: flexible sensors, wearable heaters, energy storage and conversion electrodes. We report the preparation of a highly-oriented graphene-based film prepared from liquid crystal dispersion of graphene oxides (GOs). We observed that the liquid crystal behavior of GOs is highly affected by the lateral size of GO flakes: the critical concentration for liquid crystal formation decreased with the increase of the lateral size of GO flakes, which is in a good agreement with Onsager's theory. As a result, we were able to obtain highly-ordered graphene assemblies with large-sized GO flakes (150 +/- 29 mu m) at relatively low concentrations. By applying the shear force, we were able to obtain highly-oriented films from liquid crystal GO flakes. After hydrogen iodide (HI) reduction, GO films showed excellent mechanical strength and electrical conductivity, which were 278% and 283% higher, respectively, than those of films made from smaller sized GO flakes (28 +/- 24 mu m).