Liquid crystalline swallow‐tailed compounds I

Abstract

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.

Binary Systems of Swallow‐Tailed and Laterally Branched Liquid Crystals and their Dielectric Behaviour

“…We used di-n-decyl-4[4-(4-n-octyloxy-benzoyloxy)-benzoyloxy]benzylidenemalonate (WEISSFLOG et al 1984 For comparison we took the non-branched 1,4-bis-4-n-hexylbenzoyloxy-benzene.…”

“…There are numerous classes of manyfold branched, discotic and bowlic liquid crystals. Swallow-tailed substances possess pronounced smectic properties due to the antiparallel arrangement of molecules in the short range order (WEISSFLOG et al 1984). Dielectric measurements are an appropriate method to investigate this arrangement because antiparallely oriented molecules lead to the decrease of dielectric constants and absorption intensities in parallel direction (BORDEWIJK, DE JEU;KRESSE et al 1980, KRESSE et al 1988.…”

Chemical Structure and Mesogenic Properties

“…Weissflog et al [201] were able to show that the clearing temperatures with increasing length of the two terminal chains of the swallow tail, after passing a minimum, increase ( Figure 13). This may be considered to indicate a somewhat stretched and parallel orientation of the two alkyl chains.…”

“…3.3.2 of this Chapter) the latter are large enough, they may themselves be considered as mesogenic units and the compounds that contain them then represent a new class of twins. By means of systematic elongation of the lateral substituents, Weissflog et al [220,221] have produced examples of this kind of compound (Table 44). …”

Dielectric investigations on a binary system showing a “filled” SA Phase

“…For the investigations the DST compound 4,4'-bis(di-n-octyl 4-carbonyloxy-benzylidenemelonate)-biphenyl (WEISSFLOG et al 1984) (WEISSFLOG et al 1985). The second compound is the terminal strong polar 4-cyano-phenyl 4-(4-n-hexyl-benzoyloxy)-2-methyl-benzoate which has an enlarged nematic phase range (KRESSE, SCHUHMACHER) : …”