Broad Nematic Phases with High Clearing Points

Unbranched 4-(4′-alkylbenzoyloxy)-, 4-(4′-methylanlinobenzoyloxy)- and 4-(4′dime thylaminobenzoyloxy)benzylidene-4″-cyanoanmlines were synthesized. They show broad nematic phases with high nematic isotropic transitions. Lateral Clsubstituents decrease the clearing points of these liquid crystals by about 80°. The intermediate 4-(4′-alkylbenzoyloxy)benzaldehydes are monotropic nematic.     

Stable Liquid Crystals with Large Negative Dielectric Anisotropy. Part IV

Stable liquid crystals with negative dielectric anisotropy containing the bicyclo [2.2.2]octyl group were synthesized. The incorporation of this moiety in the molecules increased the thermodynamic stability of the mesophase and lowered the smectic tendency. These new compounds can be useful in liquid crystal mixtures for homeotropic nematic displays.     

Polyesters from 12-hydroxymethyltetrahydroabietic acid and 12-hydroxymethyltetrahydroabietanol

The polyester of 12-hydroxymethyltetrahydroabietic acid was prepared by the selfcondensation of the hydroxy acid (I) and from its methyl ester (II). The condensation reaction was studied and different catalysts investigated. The inherent viscosity of the polymers were measured and their DTA diagrams taken. A polyurethane as well as different polyesters of the diol (III) with methylene di-p-phenyl diisocyanate, terephthalic, adipic, suberic, and sebacic acids were synthesized. Mixed polyesters and polyamide ester were also prepared. The properties of the above described polymers were investigated and their behavior on DTA reported.     

Effect of cyclodextrin nanocavity confinement on the photorelaxation of the cardiotonic drug milrinone

We report on steady-state UV-visible absorption, emission, and picosecond emission studies of milrinone (MIR) drug in neutral water and complexed to cyclodextrins (alpha-, beta-, gamma-CD and dimethyl-beta-CD (DM-beta-CD)). The results reveal that MIR forms a 1:1 inclusion complex with CD. Upon encapsulation the emission intensity increases and the fluorescence lifetime changes from approximately 65 ps to 240-350 ps, indicating a confinement effect of the nanocages on the photophysical behavior of the drug. Due to its methyl groups, the DM-beta-CD complex shows the largest effect. The time-anisotropy experiments support the formation of 1:1 inclusion complexes and indicate motion of the drug inside the nanocavity. Furthermore, results of PM3 calculations combined with spectral and dynamical data show that the drug is not fully embedded into the cavities, and the conformation of the included complex explains the relatively short lifetimes and low emission quantum yields of these entities.     

High‐Density Polyethylene Micro‐ and Nanocomposites: Effect of Particle Shape,Size and Surface Treatment on Polymer Crystallinity and Gas Permeability

Summary: High‐density polyethylene (HDPE) micro‐ and nanocomposites with spherical and platelike inclusions were prepared and the effect of filler particles on polymer crystallinity and gas permeability was investigated. Platelike inclusions strongly reduce the polymer permeability coefficient, while spherical ones have no influence on it, irrespective of their size. The reduction in gas permeability depends on the average aspect ratio of the inclusions, which in turn depends on the exfoliation of the organo‐montmorillonites (OM) and consequently on its surface treatment.

A TEM micrograph of 3 vol.‐% 2C18 · M‐HDPE nanocomposite, showing partial exfoliation of the organo‐montmorillonite.     

Activated nitriles in heterocyclic synthesis: Novel syntheses of 3H-1,2,4-triazolo-[1,5-a]pyridine derivatives

A new route for the synthesis of 3H-1,2,4-triazolo[1,5-a]pyridines 7a–j , 12a , b , and 17a , b utilizing the reaction of the hydrazones of cyanoethanoic acid hydrazide 3a , b with ylidene malononitriles 2a–e , malononitrile, and 3-aminocrotononitrile is described.