Liquid-crystallinity of cubic phase of BABH(6) through thermal analysis of solid–solid phase transitions

• Clarification of complicated phase relation of a cubic mesogen by DSC and microscopy.
• Irregularly tiny and spiky anomalies in DSC trace upon collapse of crystals.
• Crystal growth by visiting the cubic phase.
• Demonstration of liquid-crystallinity of the cubic phase.

Phase transition behavior of 1,2-bis(4′-n-hexyloxybenzoyl)hydrazine (BABH(6)) was studied by differential scanning calorimetry (DSC) and polarizing microscopy. While the DSC trace above melting temperature is consistent with the existing report, it is not for crystalline states. A number of tiny and spiky anomalies was observed in the first cooling run whereas the number of anomalies decreases, and finally disappeared in repeated runs. Microscopic observation revealed that the tiny and spiky anomalies arise from collapsing of crystals. When the sample was cooled from the cubic phase (430 K), the tiny and spiky anomalies revived on the cooling process, which can be ascribed to the liquid-crystallinity of the cubic phase.