High temperature antiferroelectric smectic phase composed of banana-shaped achiral

Abstract

In this paper a report is given on a fluorinated compound, composed of banana-shaped molecules snowing antiferroelectric behavior in the high temperature smectic 63 phase. Dielectric studies performed in the frequency range between 10 Hz and 13 MHz revealed two broad peaks in the low frequency dielectric spectrum of B2 phase. There is only one complex relaxation process in the B₁ phase that transforms into a glassy state where the molecular process responsible for the dielectric spectrum is being frozen out. The Vogel-Fulcher model has been applied to describe temperature dependence of the relaxation time in the vicinity of the glassy transition that is characterized by T_o = 303.95 K and Tg = 316.46 K. At the end some possible mechanisms of dielectric relaxation processes observed will be discussed. Spontaneous polarization computed by integrating of the polarization current peaks is equal to ca. 400 nC/cm² for the B₂ phase.

Key Words:

• banana-shaped molecules
• dielectric spectroscopy
• collective and molecular processes
• spontaneous polarization
• glassy transition