Figure 4

Recovery of gleaming defects through phase transitions.

The initial states at room temperature (in the nematic state) observed by POM and FOM are shown for both System-(i) (a) and System-(ii) (b). As soon as the liquid crystal becomes isotropic on elevating temperature (~36 °C), the gleaming defects (white arrows) disappear and homogeneous fluorescence intensity is observed. The gleaming defects reappear soon after the transition to the nematic state. In System-(i), the defects reappear at almost the same positions, which is probably due to the surface memory effect^29,30,31. The average intensity in the isotropic state is lower than that in the nematic one, because of the random distribution of the orientation of the transition moment of fluorescent molecules P, in contrast to its distribution in the xy plane in the nematic state (see main text). In System-(ii), the average intensity in the isotropic state is higher than that in the nematic state. This is due to the hybrid alignment formed in System-(ii)^12,22,24,32 in the nematic state; near the liquid crystal-air boundary, P is almost parallel to the optical axis and therefore the fluorescent molecules are hardly excited. (Scale bars: 20 μm).