Investigations of nematoids using polarizing microscopy and Pluta birefracting microinterferometry

摘要

Some multicomponent liquid crystal systems show unusual behavior in the phase transition from the isotropic melt to the mesomorphic state. In these systems, the nucleation is performed in the form of filaments, called nematoids, freely suspended in the isotropic melt. The observed aspect ratio (diameter : length) of the nematoids achieves 1:3000. Matured nematoids are rather unstable and undergo rapid shrinkage to droplets. The main features common to essentially all nematoids in the multicomponent (nematic, smectic B, and non-mesogenic chiral dopant) systems are: they can split into two separate threads surrounding homeotropically oriented smectic 'lake' or can undergo the segmentation or double-spiralling before their transformation to droplets. To confirm the supposition that these processes develop the bifilar organization of the nematoids, the microinterferometric analysis was performed by using the Pluta birefracting microinterferometry. This analysis supports the conception that the nematoids represent multiphase systems and are composed of two parallel planar nematic filaments connected with homeotropically oriented smectic wall (gluon). To adjust the mutually perpendicular orientation of molecules, the peripheral filaments and gluon are assumed to be connected with chiral interface. Presumably, the creation of the nematoids is the result of the phase separation in a system with anisotropic surface tensions. It is possible that instability with respect to the segmentation of the nematoid filaments is caused by the anisotropy of the surface tensions at the interfaces within a nematoid whereas the double-spiraling can be the result of a phase transition of the gluon connecting both the filaments or within the chiral interfaces.