Chiral-racemic phase diagrams of blue-phase liquid crystals

Abstract

We have measured the phase diagrams of mixtures of chiral and racemic CE4, CE5, and CE2 in order to study the effect of varying chirality on the existence of blue phases in chiral liquid crystals. We observe three blue phases—BPI, BPII, and BPIII—which progressively appear at the isotropic phase boundary as the chirality is increased. The temperature widths of both BPI and BPIII become wider with increasing chirality, while BPII becomes narrower and vanishes at high chirality. We argue that this may be a universal feature of blue-phase temperature-chirality phase diagrams and discuss our results in light of previous theory and experiment.