A Comparison of the Optical and Steric Tilt in Antiferroelectric Liquid Crystals

Abstract

X-ray and optical techniques have been employed to study six materials that exhibit frustrated chiral smectic phases across the entire tilted phase range. The layer spacings are used to deduce the steric tilt angle of the systems which are compared with optical tilt of the phases. In general, the steric tilt is lower than the X-ray tilt, as would be expected. There is evidence of conformation driven inversion phenomena in three of the materials. The ratio of the tilts is strongly temperature dependent in all but two of the materials, and in three of the materials the x-ray tilt is higher than the optical tilt over part of the SmC*phase. The results are discussed in terms of molecular conformations.

Key Words:

• ferroelectric
• antiferroelectric
• x-ray diffraction
• liquid crystal