Electrooptic and Dielectric Spectroscopy Measurements of Binary Chiral-Dopant Antiferroelectric Mixtures

Abstract

Recent examinations on binary chiral-dopant antiferroelectric liquid crystalline mixtures revealed an unusual switching behaviour. In order to investigate the switching processes that take place in the mixtures, both in the bulk and as influenced by surfaces, further electrooptic and dielectric spectroscopy studies have been carried out on two model binary mixtures in the induced SmA*, SmC* and SmC_A* phases. The dielectric spectra feature the different modes typical for these phases, but of varying purity, indicating a more complex phase behaviour than expected. The electrooptic behaviour in the antiferroelectric phase varied from clearly antiferroelectric to near hysteresis-free switching directly between ferroelectric states. We conclude that the phase sequence, and consequently switching behaviour, is a function of both the type of dopant used and of the strength of the surface interactions (cell thickness). In thin cells synclinic (ferroelectric) ordering appears to be favoured.

Key Words:

• liquid crystal
• antiferroelectric
• chiral-dopant mixture
• dielectric spectroscopy
• electrooptics