Cellular structures arising from viscoelastic phase separation in binary mixtures of thermotropic liquid crystals

Abstract

Viscoelastic effects are known to influence pattern formation during phase separation in dynamically asymmetric mixtures. Evidence is shown for such an effect in some binary mixtures composed of liquid crystals made of rod-like (R) and bent-core (BC) molecules. The difference in dynamics at phase separation manifests itself in the form of cellular structures (CSs). This is mainly driven by dissimilarities in flow and rotational viscosities of the two types of molecules which differ in size and shape. The heterogeneous structure has been characterized by optical and confocal microscopy along with X-ray diffraction studies and found to be composed of coexisting liquid crystalline phases. The striking resemblance to CSs of biological systems further enriched by topological defects is unique to this system. The morphology and stability of the CSs are dictated by the smectic ordering influenced by the relative concentration and mutual orientation of the R and BC molecules. This type of phase separation process can also be utilized to form functional ordered assemblies of nanoparticles embedded in a liquid crystal matrix.