Rotatory Sense and Pitch of Cholesteric Liquid Crystals

Abstract

Cholesteryl compounds can be either right-handed or left-handed cholesteric liquid crystals. It is shown that the cholesteryl skeleton is effectively right handed, and that additions at the 3β-carbon of the first ring tend to reduce the right handedness, i.e., increase the pitch. This effect can be expressed as 1/λ0=1/np=7.5d−15.6, where d is a distance measured in the direction of the 3β-carbon bond direction. For d>2.08 Å the liquid crystals become left handed, and the pitch now decreases with increasing distance d.