Tilt-polarization coupling in a homologous series of ferroelectric liquid crystals

The synthesis of the homologous series 4-[(S)-2-chloro-4-methylpentanoyloxy]-4′-[4-alkylbenzoyloxy]biphenyl and their chiral and mesomorphic properties are reported. The enantiomeric excess is deduced from 1H NMR spectroscopy. For the hexyl derivative, a twist grain boundary state (TGBA*) mediates the cholesteric to SmC* phase transition and its stability is discussed in terms of chirality and surface interactions. In the SmC* phase, measurements of the spontaneous polarization are reported and the temperature dependence of the tilt angle is determined from the electro-optical switching process or deduced from X-ray measurements of the smectic layer thickness, respectively. The tilt-polarization coupling is discussed within the framework of the ‘generalized Landau model’ proposed by Žekš and Blinc.