Unusual patterns in the growth of smectic liquid crystals

Abstract

Smectic liquid crystals have a layered arrangement of rod-like organic molecules. In the smectic A phase the average orientation direction of the molecules is parallel to the layer normal while in the smectic C, it is at an oblique angle. Usually when smectic A liquid crystals separate from the isotropic phase, they do so in the form of short rod-like structures called "batonnets" which are made of focal conic domains. It is now known that the batonnets arise because of the positive interfacial tension anisotropy γ∥ - γ⊥ of the smectic, in which the subscripts refer to directions ~arallel and perpendicular to the layer normal.In the present article we summarise our recent studies on some binary systems in which γ∥ - γ⊥ is negative, leading to some unusual structures like highly elongated cylinders which are stabilised by concentration gradients. We find other novel structures like discs, and 'ink-bottles' etc, when the interfacial tension anisotropy changes sign during the growth of smectics. In the smectic C phase, we find additional dynamics when the cylinders grow; soliton-like objects are generated at one end and propagate along the cylinder to the other end. Further, the cylinders as a whole have physical locomotion as they grow from the isotropic phase. We discuss the results in terms of simple physical models.