Influence of temperature and terminal chain length on helical pitch in homologue series nH6Bi

Abstract

The homologous series of three ring chiral esters with terminal chains, one 1-methylheptyl group and, one alkanoyloxyhexyloxy group, were studied. Compounds of these series are liquid crystals with smectic phases, that is, SmA, SmC* (ferroelectric phase) and SmC*_A (antiferroelectric phase). The helical pitch was measured by a spectrophotometric method of selectively reflected light. It was found that the helical pitch increases and then decreases with temperature in the SmC*_A phase for most homologues and in the SmC* phase for one homologue. The temperature characteristics of the helical pitch are related to the change in handedness of the helix.

Keywords:

• liquids crystals
• ferroelectric phase
• antiferroelectric phase
• helical pitch
• helical twist sense

Acknowledgement

This work has been carried out under grant PBW-514.