Direct observation of columnar liquid crystal droplets

While the columnar liquid crystalline phase in suspensions of plate-like colloids is by now well-established, little is known about the pathway leading to the formation of this highly ordered, self-assembled structure. Here, we present direct observations of the morphology and structure of micrometer-sized droplets of the columnar phase formed in the nematic phase in suspensions of colloidal gibbsite plates. From polarized light microscopy and optical Bragg reflection measurements we deduce that these droplets consist of stacks of platelets in a hexagonal arrangement, forming a disk-shaped droplet. We discuss the relation of this droplet structure to the nucleation pathway of the columnar phase and to the anisotropic nematic-columnar interfacial tension.