The effect of metal oxides on the oxidation of polybutadiene

Carboxy-terminated polybutadiene (CTPB) was oxidised as a coating on various metal oxides by heating in air on a thermobalance. The oxidation was found to be free from diffusion control and was catalysed by certain of the oxides. The catalysis was shown to be independent of semiconductor type and to be associated with those oxides for which the width of the forbidden zone between the valence and conduction bands (U) is less than 1.9 eV. In general, low values of U result in high catalytic activity. It is proposed that catalysis occurs by a redox mechanism, viz. RO₂H + p → RO₂^. + H⁺, RO₂H + e → RO^. + OH^?.     

Thermal density fluctuations in amorphous polymers as revealed by small angle X-ray diffraction

Summary Thermal density fluctuations in amorphous polymethyl methacrylate, polycarbonate and polyethylene terephthalate were studied by means of small angle X-ray scattering. The measurements were performed in a temperature range from 20 °C up to about 50 °C above the glass transition temperatureT _g of the individual sample.AboveT _g the experimental values of the fluctuations are proportional to the isothermal compressibility and the temperature of the sample as predicted by the fluctuation theory for a system in thermodynamic equilibrium.At temperatures belowT _g this relation is no longer correct. The experimentally determined fluctuations are now proportional to the compressibility of the sample in the equilibrium state atT _g and to the actual temperature of the glassy sample. By considering a statistical ensemble with exchange of energy, particles and order between the systems of the ensemble an equation can be derived for the fluctuations of the number of particles per given volume which predicts the observed behaviour. The order parameter takes into account the fact that the properties of the glassy state depend on the way by which the state was produced.

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Zusammenfassung Es wurden thermische Dichtefluktuationen in amorphem Polymethylmethacrylat, Polycarbonat und Polyäthylenterephthalat mit Hilfe der Röntgenkleinwinkelstreuung untersucht. Die Messungen erstrecken sich über einen Temperaturbereich von 20 °C bis zu etwa 50 °C oberhalb der GlastemperaturT _g der jeweiligen Probe.In Übereinstimmung mit den Ergebnissen der Fluktuationstheorie sind die Fluktuationen oberhalb vonT _g proportional zur isothermen Kompressibilität und zur Temperatur der Probe.Unterhalb der Glastemperatur ist diese Beziehung nicht mehr erfüllt. Hier ist die Fluktuation proportional zur Kompressibilität der Probe im Gleichgewichtszustand beiT _g und zur Temperatur. Auf der Basis einer statistischen Gesamtheit mit der Austauschmöglichkeit von Energie, Partikel und Ordnung zwischen den Systemen der Gesamtheit kann eine Beziehung für die Dichtefluktuation abgeleitet werden, die mit den experimentellen Ergebnissen übereinstimmt. Der zusätzliche Ordnungsparameter berücksichtigt die Tatsache, daß die Eigenschaften im Glaszustand wegabhängig sind.

     

Mikrobestimmung von Kohlenstoff und Wasserstoff, sowie von 14C, Tritium und Deuterium im Stickstoffstrom

Zusammenfassung Eine mikroanalytische Kohlenstoff-Wasserstoffbestimmung wird beschrieben, bei der die organische Substanz im Stickstoffstrom verbrannt und deren Crackprodukte mit Sauerstoff oxydiert werden. Halogene und Schwefel werden vom Verbrennungskatalysator (nach Körbl) absorbiert, während eventuell entstandene Stickoxide an einer Kupferschicht zur Reduktion gelangen. Die entstandenen Verbrennungsprodukte CO₂ und H₂O können gravimetrisch erfaßt oder bei radioaktiven Proben durch entsprechende Absorptionsmöglichkeiten in einem Flüssigkeits-Szintillationszähler zur Zählung gebracht werden.Stark quenchende einfache, sowie doppelt markierte Proben, die man auch durch Modifikationen des Zählgeräts nicht mehr genau auszählen kann, können mit gleich hoher Zählausbeute wie nichtquenchende erfaßt werden (75% für ¹⁴C und 30% für ³H), da keine störenden Fremdgase die Zählung beeinflussen.Deuterium wird durch Ausmessen der OD-Bande bei 2500 cm^–1 mit einem Infrarot-Spektrometer quantitativ bestimmt.

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Microanalytical determination of carbon and hydrogen, ¹⁴C, tritium and deuterium in a stream of nitrogen

A microanalytical method for the determination of carbon and hydrogen is described. The procedure involves the combustion of the organic substance in a stream of nitrogen and the oxidation of the decomposition products with oxygen. Halogens and sulphur are absorbed by the combustion catalyst (according to Körbl), whereas nitrogen oxides are reduced on a copper surface. The combustion products, CO₂ and H₂O are determined gravimetrically; in the case of radioactive samples they are appropriately absorbed and counted in a liquid scintillation counter. Strongly quenching singly and doubly labelled samples, which cannot be accurately counted even by modification of the counting device, give equally high radioactive yields (75% for ¹⁴C, 30% for ³H), since counting is not influenced by other gaseous impurities. Deuterium is quantitatively determined by measuring the intensity of the OD-signal at 2500 cm^–1 with an infrared spectrometer.

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Herrn Prof. Dr. H. Schmid bin ich für das wohlwollende Verständnis meinen Arbeiten gegenüber zu bestem Dank verpflichtet. Sämtliche Glas- und Quarzgeräte wurden in der Glasbläserei unserer Institute von Herrn B. Thueler angefertigt, wofür ich auch ihm an dieser Stelle danken möchte.     

Autoxydationsprodukte des Guaiazulens

Zusammenfassung Guaiazulen wird bei Luftzutritt durch Autoxydation verändert. Die dabei auftretenden Produkte wurden chromatographisch aufgetrennt und die drei als Hauptmenge auftretenden Verbindungen charakterisiert: 3.3-Diguaiazulenyl, 1.4-Dimethyl-3-(3-guaiazulenyl)-6-isopropyl-5H-inden-5-on, 1.4-Dimethyl-3-(3-guaiazulenyl)-5-oxo-6-isopropyl-5H-inden-7-aldehyd.

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Autoxidation products of guaiazulene

Guaiazulene exposed to air undergoes autoxidation. The products were separated by chromatography, and the three major products characterized: 3.3-diguaiazulenyl, 1.4-dimethyl-3-(3-guaiazulenyl)-6-isopropyl-5H-inden-5-one, and 1.4-Dimethyl-3-(3-guaiazulenyl)-5-oxo-6-isopropyl-5H-inden-7-aldehyd.

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Herrn Prof. Dr.H. Nowotny gewidmet.     

Neutronenaktivierungsanalytische Bestimmung von Osmium in Geologischen Proben

A neutron activation analysis procedure was developed for the determination of osmium in geological materials. The method consists in the measurement of the 129.4 keV γ-rays of¹⁹¹Os after radiochemical separation of osmium. The sample decomposition, the chemical separation process and the optimal measuring conditions are described and discussed.      

Distribution of polymer deposition in plasma polymerization. III. Effect of discharge power

Distribution of polymer deposition in an inductively coupled rf discharge system is studied as a function of level of discharge power with acetylene and styrene as monomers. When a fixed flow rate is used, the discharge power has a relatively small effect on the pattern of distribution of polymer deposition as long as values of W/FM, where W is discharge wattage, F is flow rate, and M is molecular weight of monomer, are maintained above a critical level to maintain full glow in the reaction tube. It has been shown that plasma polymerization of two monomers which have different molecular weights can be compared in a fair manner by selecting conditions to yield similar value of W/FM.     

Untersuchungen an Alkylmetallalkoxiden der Elemente Aluminium,Gallium und Indium. III. Eigenschaften und Schwingungsspektren von Dialkylgallium- und Indiumalkoxiden

Studies on Alkyl Metal Alkoxides of Aluminium, Gallium, and Indium. III. Properties and Vibrational Spectra of Dialkylgallium- and Indium Alkoxides The preparation and the properties of dialkyl metal alkoxides R₂MOR′ (with R = CH₃, CD₃, C₂H₅; R′ = CH₃, CD₃ and M = Ga, In) are described. The vibrational data (IR and Raman) of the trimeric methyl derivatives point to puckered six-membered M₃O₃-ring systems.     

Rapid and sensitive liquid chromatographic determination of carbamazepine suitable for use in monitoring multiple-drug anticonvulsant therapy.

A rapid, sensitive and selective method for the determination of carbamazepine and its major metabolite in plasma has been developed. Other commonly used anticonvulsants can be determined in the same procedure without interference. After extraction with dichloromethane, the components are separated by high-pressure liquid chromatography without further clean-up or concentration on a column packed with small-particle silica gel. The mean recovery from plasma is 98.6% with a relative standard deviation of 1.6%. The detection limit for carbamazepine is approximately 2 ng/ml, requiring 1 ml of plasma.     

ON THE LUMINESCENCE OF L-TRYPTOPHANE AND l-TYROSINE IN AQUEOUS SOLUTION AT 77dK INDUCED BY X-RAYS AND U.V.-LIGHT

Abstract— The lumincscence arising from L-tryptophane and L-tyrosine in aqueous solutions at 77K during irradiation with u.v.-light and with X-rays has been studied. The spectra obtained with the two types of radiation were largely similar, differing only in that the yields of phosphorescence relative to fluorescence were considerably enhanced in the case of X-irradiation. The decay times observed for the exponentially decaying phosphorescence, being 6.6 sec and 2.7 sec for tryptophane and tyrosine respectively, were the same for both kinds of irradiation. The G-value of the X-ray induced luminescence was about 10 for both tryptophane and tyrosine. Thus, about 30 per cent of the total energy absorbed from X-rays in these compounds was re-emitted as light.
It was concluded that the X-ray induced fluorescence and phosphorescence originate from the same levels as does the luminescence caused by u.v.-light, i.e. the lowest excited singlet and the lowest triplet level of the aromatic structure of these compounds. In the case of X-irradiation the enhanced ratios between the yields of phosphorescence and fluorescence indicated that some process other than excitation directly from the ground state contributed considerably to the luminescence yields. Assuming this process to be a recombination between the ionized molecule and its electron, it was calculated that the contribution to the luminescence yield from excitations directly from the ground state relative to that from ionizations, was negligible for both compounds.     

Wellenmechanische Absolutrechnungen an Molekülen und Atomsystemen mit der SCF?MO?LC(LCGO) Methode. IV. Das Äthylen (C2H4)

The C₂H₄ was investigated ab initio for the equilibrium distance of the centers, taking all 16 electrons into account, using the Allgemeines Programmsystem/SCF ? MO ? LC (LCGO ) Methode. A total energy of ?76.77 a.u. and an ionization energy of 10.55 eV were found.