Electroclinic and antiferroelectric properties of (R)-(–)-nonan-3-yl 4-(4′-dodecyloxybiphenyl-4-yicarbonyloxy)-3-fluorobenzoate

Abstract

The synthesis of the novel chiral mesogen (R)-(–)-nonan-3-yl 4-(4′-dodecyloxybiphenyl-4-ylcarbonyloxy)-3-fluorobenzoate and a discussion of its various liquid-crystalline properties are reported. Initial optical microscopy studies revealed the presence of a smectic A* phase and what was at first thought to be a smectic C* phase; further examination of this compound as thin film preparations revealed the presence of s± 1/2 disclinations suggesting that the phase is an antiferroelectric subphase. Furthermore, these observations were supported by results from both differential scanning calorimetry and contact miscibility studies using known smectic C*_A standards. The antiferroelectric nature of the phase was confirmed by obtaining sharp threshold characteristic curves during electrical switching studies from the antiferroelectric to an induced ferroelectric phase. Additionally, the chirality of the compound results in a reduction in the environmental symmetry for the smectic A* phase, and this allows electroclinic switching in the pretransitional region of the smectic A* phase close to the smectic C*_A transition to take place under suitable conditions.