Behaviour of Smectic Phases in Free Standing Film Geometry: Discontinuous Change in the Tilt Angle of Polar Smectic Phases at the Phase Transition Temperature

Abstract

The temperature dependence of the thickness of thick freestanding Films (FSF) is studied using a novel high resolution film thickness measurement technique. A small discontinuity in the temperature dependence of the smectic tilt angle at every phase transition between the ferro-, ferri-, antiferroelectric phases is observed. An additional term in the total free energy which considers an interaction between the neighboring and the next neighboring smectic layers explains this discontinuity. A comparison of the experimental results with phenomenological theory suggests that the long-range interactions are inversely proportional to the square of the distance between the layers.

Keywords:

• Smectic phases
• chiral smectic liquid crystals
• antiferroelectric and ferroelectric liquid crystals
• tilt angle
• spontaneous polarization
• free-standing film
• thickness measurements
• polar interactions between (next) neighboring layers
• thickness jump ratio

PACS numbers:

• 64.70.Md
• 61.30.Eb
• 61.30.Cz
• 06.30.Bp
• 78.40.-q
• 77.80.-e