By reaction of di-n-alkyl 4-hydroxybenzylidene-malonates with different acid chlorides three homologous series of swallow-tailed compounds were synthesized. The products were characterized by microscopic and caIorimetric investigations and show nematic and smectic behaviour. As X ray studies prove the relatively broad molecules are statistically antiparallel arranged within the smectic monolayers.Diirch Umsetzung von 4-Hydroxybenzyliden-malonsaure-di-n-alkylestern mit verschiedenen Saurechloriden synthetisierten wir drei Reihen von ,,Swallow-Tail-Verbindungen". Die Produkte wurden durch mikroskopische und kalorimetrische Untersuchungen charakterisiert und zeigen nematisches und smektisches Verhalten. Wie Rontgenuntersuchungen zeigen, sind die relativ breiten Molekiile innerhalb der smektischen Monoschichten statistisch antiparallel geordnet.

possess smectic C phases and at lower temperatures additional optically isotropic phases. According to X-ray investigations these isotropic phases show cubic symmetry. The lattice units consist of aggregations with micellar dimensions. The substances were characterized by microscopic, dilatometric and calorimetric investigations. The new cubic mesophases do not exhibit complete miscibility with the "smectic D" phases.

The substances of the homologous series with n = 6, 12, 14, 15, 16, 18 were investigatec .y calorimetry and microscopy. I n the lower nienibers exist nematic, smectic A and smectic C phases, in the homologs with lz = 16 and 18 appear phases of the type smectic D with cubic structure. The kinetics of these phase transitions, in which smectic D is participating shows a strong dependence upon the experimental conditions. Supercooling, as well as, overheating effects were found. I n the supercooled state we could detect for the first time smectic phases, which are metastable with respect to another liquid crystalline phase (SD).Die Substanzen der homologen Reihe mit n = 6, 12, 14, 15, 16, 18 wurden kalorimetrisch und mikroskopisch untersucht. An den niederen Gliedern treten nematische und smektische A-und C-Phasen auf, an den Homologen mit n = 16 und 18 existieren Phasen des Typs smektisch D mit kubischer Struktur. Die Kinetik der Phasenuniwandlungen, an welchen smektisch D beteiligt ist, zeigt eine starke Abhangigkeit von den experimentellen Bedingungen und laat sowohl Unterkuhlungs-als auch Uberhitzungserscheinungen erkennen. I m unterkuhlten Zustand konnten erstmals sinektische Phasen nachgewiesen werden, die gegenuber einer anderen kristallin-flussigen Phase (S,) metastabil sind.

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Liquid‐crystalline Heterocycloalkanes. I. Synthesis and Properties of Substituted 1,3‐Dioxanes The synthesis of 2,5‐disubstituted 1,3‐dioxanes is described, their melting and clearing points and their physical properties (dielectric anisotropy, viscosity, transition enthalpies, optical birefringence) are investigated. The cyano substituted 1,3‐dioxans 5 and 7 are valuable materials for application in displays.