Optical activity in CE6 A new metastable blue phase?

Abstract

The optical rotation of a mixture of 60 per cent of chiral and 40 per cent of racemic CE6 as an 18 μm thick sample placed between glass plates treated with PI has been measured. This mixture exhibits one blue phase (BP1) on heating over a temperature range of about 0·1°C. On cooling the sample on the other hand, the BP region is expanded to 0·6°C and is divided into two regions. One region (BP1) (of range about 0·38°C below the isotropic–blue phase transition) shows two Bragg wavelengths which increase with decreasing temperature. For the second region (BPS) (of range about 0·22°C above the cholesteric–blue phase transition), one Bragg wavelength decreases with decreasing temperature, and a third Bragg wavelength appears. At constant temperature both phases remained stable for a period of several days.