A binaphthyl derivative with a wide temperature range of a blue phase
We prepared a binaphthyl derivative possessing two 2,3-difluoro-1,4-diphenylbenzene units, and then investigated the phase transition behaviour. On cooling, the compound was found to exhibit a phase sequence of iso liq–blue phase–smectic phase. The temperature of the blue phase with a cubic structure was about 30 K. An electric-field-induced phase transition was observed in the blue phase. On heating, the compound exhibited marked phase separation. Some regions showed a phase sequence of cryst–chiral nematic (N*)–blue phase (BP)–iso liq, whereas others showed that of cryst–iso liq. The temperature range of coexisting crystal and iso liq phases was about 29 K. The phase separation is quite unusual for a single compound. The phase-transition behaviour is discussed in terms of the molecular shape of the binaphthyl derivative.