Liquid Crystal Phase and Gelation of the Monodisperse Nanosheet Colloids of Magnesium Hydroxide

Here, we demonstrate liquid crystalline (LC) phase formation and gelation phenomena in the colloidal dispersion of magnesium hydroxide monodisperse nanosheets (Mg-Tris-mNS) with highly regulated hexagonal shape and size. Visual observation with crossed polarizers revealed nematic textures with interference colors due to birefringent LC phases in a Mg-Tris-mNS colloid after concentrating the colloid to 0.7 wt %. At 3 wt %, the colloid became a nematic physical gel. Small-angle X-ray scattering revealed that the nanosheet-nanosheet distance in the LC phase is smaller than theoretically expected, indicating that the nanoshee-nanosheet repulsion is partly screened by the coexisting ammonium species. The cationic nanosheets with liquid crystallinity and gelation capability presented here will be applicable for biosensing and the synthesis of inorganic/polymer nanocomposites.