Thermal phase transition behaviours of the blue phase of bent-core nematogen and chiral dopant mixtures under different boundary conditions†
We have investigated dramatic changes in the thermal phase transition of a liquid-crystalline (LC) blue phase (BP) consisting of bent-core nematogen and chiral dopants under various boundary conditions during cooling from the isotropic phase. Blue phase III, which has arbitrary morphological characteristics, between two glass plates goes to blue phase I, which has a body-centred cubic structure, when the sample is placed on the glass as a droplet form. These two distinctive phase transition behaviours were directly observed by polarized optical microscopy as well as selective reflection spectroscopy, in which the phase transition between BPs started from the air/LC interface. We determined that this transition resulted from the ordered double-twisted cylinders near the air-boundary by confocal laser-scanning microscopy.