Abstract
Smectic-A domains with defects in an isotropic phase have been observed in the mixture of octyloxycyanobiphenyl and dodecyl alcohol using a polarizing microscope. Polarizing-microscope images of possible structures are simulated to determine defect structures of the smectic-A domains. The most frequently observed focal conic domains in a smectic-A phase bounded by substrates are those consisting of confocal pairs of ellipse and hyperbola. In our experiments, the observed focal conic domains in an isotropic phase are those consisting of pairs of circle and straight line. We show that the defect structures of the smectic-A domains in an isotropic phase are not influenced by substrate surfaces and hence are a good system for observing clear geometry of defect structures.
