Psinversion in three homologous series of ferroelectric 5-(2-fluoro-alkyloxy)-2-(4-n-alkylphenyl) pyrimidines

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Abstract
We synthesized members of four homologous series of the general formula Most of the compounds exhibit smectic phases with negative PS, at higher temperatures, changing the sign to give positive PS, at lower temperatures. The inversion temperatures and PS, at a reduced temperature show alternating behavior. The tilt angles measured by X-rays as well as by electrooptical investigation do not possess any anomaly at TPS, and in several cases are practically constant. We discuss the molecular arrangemeit in C and C* phases. In order to explain the PS behavior we use the molecular statistical theory developed by Osipov et al. In this theory Ps is determined by the chiral dipole, the steric dipole and the polarizability properties of the molecules; the interplay of these properties characterizes the binding site. By opposite signs of dipolar and quadrupolar coupling of the molecules and the temperature dependence of the steric dipoles, the Ps inversion can be explained.