Stable Ferroelectric Liquid Crystals Derived from Salicylaldimine-Core

Five pairs of enantiomers derived from salicylaldimine-core have been prepared by condensing (R)- or (S)-4-(octan-2-yloxy)­anilines with 4-formyl-3-hydroxyphenyl 4-(n-alkoxy)­benzoates. They have been designed to probe the correlation between molecular structure and mesomorphism, and especially to provide stable mesogens having potential for applications in ferroelectric liquid crystal devices. Thus, they have been substituted with a chiral tail at one end and by n-alkoxy chains of varying length at the other terminal. A detailed study confirms an indistinguishable behavior of all ten mesogens exhibiting an enantiotropic chiral smectic C (SmC*) phase besides blue phase (BP) and chiral nematic (N*) phase. The SmC* phase occurring over a 50–70 °C thermal width shows ferroelectric switching with spontaneous polarization (P s) value crossing over 100 nC/cm2. Circular dichroism spectroscopic study of the mesophases confirms the chromophores of the molecules being in the macroscopic chiral (helical) environment.