Das dielektrische Verhalten von Polyäthern zwischen Mikrowellen- und Infrarot-Gebiet

Zusammenfassung Es wurde die Absorption und Dispersion verschiedener Polyäther im Mikrowellengebiet und im fernen IR untersucht. Mit wachsender Sauerstoffzahl in der Kette werden die Torsions- und Biegeschwingungen wachsend IR-aktiv. Ihre Frequenzlagen ändern sich mit dem zunehmend polaren Charakter der Struktur. Die Analogie zwischen der Verschiebung der Schwingungsfrequenzen und dem Verlauf der Schmelztemperaturen wird diskutiert.Mit zunehmend polarem Charakter steigen der Temperaturkoeffizient der Molpolarisation und die Differenz (–n ²) der Dielektrizitätskonstanten im Mikrowellengebiet und im optischen Bereich stark an. Ein Vergleich mit der Höhe der Dispersionsstufen im fernen IR und deren Temperaturabhängigkeit ergab, daß diese zusätzliche Polarisation nicht allein durch die IR-aktiven Banden bedingt ist. Sie muß gekoppelt sein mit dem ebenfalls stark anwachsenden Untergrundverlust im gesamten mm- und sub-mm-Gebiet.

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Summary Absorption and dispersion of several polyethers were measured in the microwave region and in the far infrared. The torsional vibrations become increasingly iractive with increasing number of oxygens in the chain. Their frequencies shift, too, in a manner analogues to the variation of the melting temperatures.The temperature coefficient of the mol polarization at 32 GHz and the difference (–n ²) between microwave and optical dielectric constant rise rapidly with increasing polar character of the structure. It was tried to correlate (–n ²) with the overall absorption of the skeletal vibrations. Height and temperature dependence of the far ir dispersion show, however, that the larger part of this additional polarization cannot be accounted for by the resonance absorption bands. It must be correlated with the background loss which extends over the whole mm and sub-mm range and also increases rapidly with increasingly polar structure.

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Mit 10 Abbildungen in 14 Einzeldarstellungen und 2 Tabellen     

Formation and Crystal Structure of [(F5TeOXe)+·SO2ClF][Sb(OTeF5)6-]

Xe(OTeF₅)₂ reacts with Sb(OTeF₅)₃ under the formation of [Xe₂(OTeF₅)₃]⁺[Sb(OTeF₅)₆]^-. From SO₂ClF solution a yellow solvate [F₅TeOXe]⁺·SO₂ClF· [Sb(OTeF₅)₆]^- is formed with the crystal data: a = 1028.1(1), b = 1040.9(1), c = 1780.2(3) pm, α = 98.07(1), β = 97.68(1), γ = 105.82(1)°, space group . The O-Xe···O fragment is essentially linear (176.1(2)°), and the two Xe-O distances are quite different 197.1(4) and 242.6(4) pm.     

Time dependence of viscosity of dilute polyisobutylene solutions

Summary Shearing at constant gradient of polyisobutylene (PIB) solutions in viscous polybutene oils results in time dependent changes of their viscosities. Two PIB fractions (M=8·10⁶ and 3.8·10⁶) have been studied in a variety of solvents, covering the viscosity range from 5 to 0.5·10⁻² poise. The overall phenomenon is similar to that already observed for polymethylmethacrylate, polystyrene, and polyethylene oxide solutions in Aroclor. Results have been discussed in terms of polymer molecular weight and concentration, solvent viscosity and gradient. The systems investigated are free from strong polar interactions and tendency toward molecular aggregation; time dependent changes of viscosity are therefore observable also for true molecularly dispersed solutions.

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Zusammenfassung Scherung mit konstantem Geschwindigkeitsgradienten von Polyisobutylen (PIB)-L?sungen in viskosen Polybuten-?len ergibt zeitabh?ngige ?nderungen ihrer Viskosit?ten. Zwei PIB-Fraktionen (M=8·10⁶ und 3,8·10⁶) wurden in einer Vielzahl von L?sungsmitteln untersucht, die den Viskosit?tsbereich von 5 bis 0,5·10⁻² Poise überdeckten. Das ph?nomenologische Erscheinungsbild ist ?hnlich dem schon beobachteten für Polymethylmethacrylat, Polystyrol und Poly?thylenoxid-L?sungen in Aroclor. Die Ergebnisse wurden hinsichtlich des Polymer-Molekulargewichts und der Konzentration, der L?sungsmittelviskosit?t und des Gradienten diskutiert. Die untersuchten Systeme sind frei von starken polaren Wechselwirkungen und von Tendenzen in Richtung auf molekulare Aggregation. Zeitabh?ngige ?nderungen der Viskosit?t sind deshalb auch für wahre molekulardisperse L?sungen beobachtbar.

     

DNAzyme amplification of molecular beacon signal

This paper reports an improved catalytic molecular beacon. Addition of the target oligonucleotide activates a DNA enzyme (DNAzyme), which, in turn, activates multiple copies of molecular beacons (MB) and gives rise to a strong fluorescence signal. In a previous design, the activated DNAzyme could oligomerize, especially dimerize, and result in inactivation of the DNAzyme. The current design avoids this problem, upon activated by the target DNA, the DNAzyme will stay constantly active. With the improved method, a detection of 10 pM DNA has been demonstrated, which is 1000 times more sensitive than the method previously reported.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XLIV. Tetrakis(alkoxycarbonylmethyl)titan-Verbindungen

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XLIII. Tetrakis(alkoxycarbonylmethyl)titanium Compounds Organotitanium(IV) compounds of the type (ROCOCH₂)₄Ti (R ? C₂H₅, i-C₃H₇, t-C₄H₉, C₆H₅, C₆H₅CH₂) were obtained by reactions of ROCOCH₂Li derivatives with TiCl₄ at low temperature. The compounds which decompose only above 90°C were characterized by the hydrolysis products, anaerobic reactions with iodine, and the i.r. spectra. The bond conditions are discussed.     

On the determination of polarity parameters of silica by means of solvatochromic probe dyes

Empirical solvent parameters of silica surfaces are determined by means of solvatochromic dyes, e.g., Cu(tmen) (acac)⁺ ClO ₄ ^– /B(C₆H₅) ₄ ^– , Fe(phen)₂(CN)₂, and Michlers Ketone dissolved in 1,2-dichloroethane or cyclohexane. The values obtained by UV/VIS-measurements are compared with both the polarity scales of Kamlet and Taft and with Gutmann's donor and acceptor numbers. Kamlet and Taft's -parameter (the hydrogen-bond donation capacity of a solvent) is determined independently by means of salicylideneaniline. The ^* of silica is determined using 5-N,N-dimethylamino-5-nitro-2,2-bithiophene and the complex of tetracyanoethylene with Michlers Ketone, respectively. Further on the reliabilities of the obtained Kamlet-Taft parameters , , and ^* are checked by comparism with experimental and calculated values of theE _T(30)-parameter of silica by means of multi-parameter regression analysis. The surface properties of silica are influenced mainly by HBD-properties (75%) and dipolarity/polarizability ^* (20%), but hardly by the HBA-properties (<5%). UV/VIS-measurements were carried out in a special equipment with glass fiber optics, A drawing of the apparatus is given.     

Die Strommer-Zykliden des Flaggenraumes

According to H. BRAUNER a flag space is a three-dimensional affine space with an absolute {,f,F}, wheref is a line in the plane of infinity andF a point onf. A cyclide is a surface of order 4 that intersects only atf. A STROMMER-cyclide is a cyclide generated by translation of a circle in an isotropic plane. In this paper we proof that all STROMMER-cyclides can be generated by translation of an isotropic circle along a divergent Newton-parabola or a conic in a full isotropic plane. We give normal-forms and CAD-pictures of these surfaces. Finaly some geometrical results about STROMMER-cyclides are developed.

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Herrn o.Prof. Dr. Gy. Strommer zum 70. Geburtstag gewidmet.