Thermal and optical properties of chiral twin liquid crystalline bis(cholesteryl) alkanedioates

Abstract

The thermal and optical properties of a series of bis(cholesteryl) alkanedioates were investigated. The melting points, the cholesteric to isotropic transition temperatures, the entropy changes at this temperature and the selective reflection wavelengths of the cholesteric phase all exhibit an odd-even effect as a function of spacer length. This is attributed to a difference in the ordering of the cholesteric phase as a function of the parity of the spacer. Because the properties of the members of the series with a short spacer could not be measured for several reasons, their properties were also determined as a 5 wt% solution in a cholesteric host. A similar odd-even influence on the cholesteric to isotropic transition temperatures and the optical properties of the host was observed as for the pure compounds. The influence on the properties of the host is stronger for compounds with a short spacer than for compounds with a longer spacer.