title: Formation of smectic phases in binary liquid crystal mixtures with a huge length ratio.
abstract: A system of two liquid-crystalline phenylpyrimidines differing strongly in molecular length was studied. The phase diagram of these two chemically similar mesogens, with a length ratio of 2, was investigated, and detailed X-ray diffraction and electrooptical measurements were performed. The phase diagram revealed a destabilization of the nematic phase, which is present in the pure short compound, while the smectic state was stabilized. The short compound forms smectic A and smectic C phases, whereas the longer compound forms a broad smectic C phase and a narrow higher-ordered smectic phase. Nevertheless, in the mixtures, the smectic C phase is destabilized and disappears rapidly, whereas smectic A is the only stable phase observed over a broad concentration range. In addition, the smectic translational order parameters as well as the tilt angles of the mixtures are reduced. The higher-ordered smectic phase of the longer mesogen was identified as a smectic F phase.
authors.affiliation: Institut für Physikalische Chemie, Universität Stuttgart, D-70569 Stuttgart, Germany.
authors.forename: Nadia
authors.initials: N
authors.lastname: Kapernaum
authors.forename: Friederike
authors.initials: F
authors.lastname: Knecht
authors.forename: C Scott
authors.initials: CS
authors.lastname: Hartley
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Roberts
authors.forename: Robert P
authors.initials: RP
authors.lastname: Lemieux
authors.forename: Frank
authors.initials: F
authors.lastname: Giesselmann