Processes occurring during the coalescence of isotopic droplets surrounded by a nematic liquid crystal were examined. Measurements were carried out in flat optical cells with hybrid molecular orientation at the boundary between the liquid crystal and the isotropic liquid and at the interface between the liquid crystal and the inner surface of the cell. Polarized optical microscopy enabled detailed characterization of the evolution of the internal orientational structure of merging droplets. At the initial stage, a bright flash is observed in the neck region between the droplets; this flash is associated with the appearance of birefringence in the plane of the sample induced by material flow. Over a broader time interval, a qualitative transformation of the orientational ordering field of the liquid crystal occurs. A cascade formation of topological defects with positive and negative topological charge and their subsequent annihilation was observed. The birth and annihilation of defects are analyzed on the basis of topological laws.
Dolganov et al. (Mon,) studied this question.