Microscopic Observations of the Cholesteric Blue Phase in Mixtures of Varying Pitch

Abstract

Theories for the blue phase proposed recently by Brazovskii and Dmitriev and by Hornreich and Shtrikman predict that this phase can exist only for cholesterics of sufficiently short pitch. In this article we demonstrate this dependence upon pitch through microscopic observations of three sets of binary mixtures, one set consisting of mixtures of cholesterics of opposite chirality and the other two consisting of cholesteric-nematic mixtures.

In the course of these studies we have developed techniques for growing particularly large platelets of the blue phase. We present photographs of these platelets demonstrating, for the first time, the optical anisotropy of the blue phase, which is evident when the platelets are sufficiently large. Characteristic twinning patterns are also evident in the photographs.