Ferroelectric liquid crystals from bent-core molecules with vinyl end groups

Abstract

New banana-shaped achiral compounds, 1,3-phenylene bis [4-14-(alkenyloxy) phenyliminomethyl}benzoate]s were synthesized by varying the length of alkenyl group; their ferroelectric properties, are described. The smectic mesophases, including a switchable chiral smectic C (Sm C*) phase, were characterized by differential scanning calorimetry, polarizing optical microscopy and triangular wave method. The presence of vinyl groups at the terminals of linear side wings in the banana-shaped achiral molecules containing Schiffs base mesogen induced a decrease in melting temperature and formation of the switchable Sm C* phase in the melt. The smectic phases having the octenyloxy group such as (CH2)(6)CH=CH2 showed ferroelctric switching, and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/cm(2) (X=H) and 225 nC/cm(2) (X=F), respectively. We could obtain ferroelectric phases by controlling the number of carbon atom in alkenyloxy chain of a bent-core molecule.