Kinetics of γ-ray polymerization of formaldehyde in the presence of carbon dioxide

A kinetic study of the γ-ray polymerization of formaldehyde in toluene solution in the presence of carbon dioxide was carried out at temperatures of + 13 to ?17°C. Two modes of the polymerization, spontaneous and γ-ray polymerization, occur in this system. The γ-ray polymerization, experimentally separated from the spontaneous polymerization, was investigated. The rate of γ-ray polymerization increased slightly with the square root of carbon dioxide concentration. The rate of polymerization was also found to be proportional to the dose rate and the square of monomer concentration. The molecular weight of polymer formed was independent of the reaction condition. The apparent activation energy was estimated to be 10.3 kcal./mole. The kinetics of the γ-ray polymerization in the presence of carbon dioxide are explained quantitatively by a cationic mechanism, and the role of carbon dioxide is as an action of retardation for neutralization of the cationic initiating species, which was produced by γ-radiation, by means of a reverse reaction with an electron. Physical and mechanical properties of the polymer obtained by γ-ray polymerization were also investigated.     

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.     

Density fluctuations in amorphous and semicrystalline polymers

Summary The small-angle scattering of amorphous and semicrystalline polymers contains an intensity component due to density fluctuations within the crystalline and amorphous domains.For amorphous polymers, the density fluctuations aboveT _g correspond to the theoretical value for a fluid system in thermodynamic equilibrium. BelowT _g , a temperature dependence proportional to T is observed over a range of about 50°. At lower temperatures, a linear relationship with a smaller slope has been found which extrapolates to a non-zero value at 0 °K. This value corresponds to the frozen-in disorder, the slope at low temperatures is related to thermal vibrations and can be evaluated in terms of photon-phonon scattering.Semicrystalline polymers show a temperature dependence of the density fluctuation similar to that of the amorphous polymers. At constant temperature the density fluctuations vary linearly with crystallinity.Natural rubber shows an increase of the density fluctuations with increasing cross-linking densities from which information on the density changes in the vicinity of a cross-link and on the statistics of the distribution of cross-linking can be obtained.

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Zusammenfassung Die Kleinwinkelstreuung amorpher und teilkristalliner Polymere besitzt eine Intensitätskomponente, die von Dichtefluktuationen innerhalb der kristallinen und amorphen Bezirke herrührt. Für amorphe Polymere entspricht die Dichtefluktuation oberhalb vonT _g dem theoretischen Wert für ein fluides System im thermodynamischen Gleichgewicht. UnterhalbT _g wird eine Temperaturabhängigkeit proportional zuT über einen Bereich von etwa 50° beobachtet. Bei tieferen Temperaturen wird eine lineare Beziehung mit einer geringeren Steigung gefunden, welche zu einem endlichen Wert bei 0 °K extrapoliert werden kann. Dieser Wert bezieht sich auf die eingefrorene Fehlordnung, die Steigung bei tiefen Temperaturen ist auf thermische Schwingungen zurückzuführen und kann als Photon-Phonon-Streuung ausgewertet werden.Teilkristalline Polymere zeigen eine Temperaturabhängigkeit der Dichtefluktuation, die der von amorphen Polymeren ähnlich ist. Bei konstanter Temperatur ändert sich die Dichtefluktuation linear mit der Kristallinität.Naturkautschuk zeigt eine mit der Vernetzungsdichte ansteigende Dichtefluktuation, aus der man Information über die Dichteänderung in der Umgebung eines Netzpunktes und die Statistik der Netzpunktverteilung erhalten kann.

     

Absolute infrared intensities of hydrocarbons

Dipole-moment derivatives, calculated by both the CNDO/2 method with different parameterizations and the INDO method, are compared to the experimental values determined from absolute infrared intensity measurements for the IR active modes of methane, ethane, ethylene and acetylene. A parameter refinement procedure is introduced in which the CNDO/2 molecular orbital parameters are adjusted through a damped least-squares treatment to give best agreement with the observed dipole-moment derivatives. It is found that the refinement does not substantially improve the agreement obtained with the original CNDO/2 parameterization. The INDO method gives somewhat poorer agreement than the CNDO/2 calculations. As an example of the applicability of the molecular orbital methods toward reproducing relative infrared intensities, the spectrum of cyclopropane in the gasphase is examined.

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Zusammenfassung Die Ableitungen des Dipol-Moments, die nach der CNDO/2-Methode mit verschiedenen Parametrisierungen sowie der INDO-Methode berechnet wurden, werden mit den experimentellen Ergebnissen aus Messungen der absoluten Infrarot-Intensitäten für die IR-aktiven Schwingungen von Methan, Äthan, Äthylen und Azetylen verglichen. Die CNDO/2-Parameter werden mit einer Methode der kleinsten Quadrate den beobachteten Dipol-Moment-Ableitungen angepaßt. Die Ergebnisse sind jedoch nicht wesentlich von denen der ursprünglichen CNDO/2-Methode verschieden. Die INDO-Ergebnisse sind nicht so gut wie die CNDO/2-Ergebnisse. Als Beispiel der Anwendbarkeit der MO-Methoden zur Berechnung von relativen IR-Intensitäten wird das Spektrum des Cyclopropans in der Gasphase untersucht.

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Résumé Les dérivées du moment dipolaire, calculées par la méthode CNDO/2 avec différentes paramétrisations et par la méthode INDO, sont comparées aux valeurs expérimentales déterminées à partir de mesures d'intensité absolue pour les modes actifs dans l'infra-rouge dans le méthane, l'éthane, l'éthylène et l'acétylène. Les paramètres sont ajustés de manière à donner le meilleur accord avec les dérivées du moment dipolaire. Cet ajustement n'améliore pas sensiblement l'accord obtenu avec la paramétrisation CNDO/2 originale. La méthode INDO donne des résultats moins bons que les calculs CNDO/2. Le spectre du cyclopropane en phase gazeuse est étudié comme exemple de l'applicabilité de la méthode des orbitales moléculaires au calcul des intensités relatives infra-rouge.

     

Cationic polymerization of formaldehyde in liquid carbon dioxide. Part I

A cationic polymerization of formaldehyde which gave a high molecular weight polymer was studied in liquid carbon dioxide at 20–50°C. In the polymerization without any catalyst both the rate of polymerization and the molecular weight of the resulting polymer increased rapidly with a decrease in the loading density of the monomer solution to the reaction vessel, and also increased with an increase in the initial monomer concentration. From these results it was concluded that the initiating species could be ascribed to an impurity contained in the monomer solution. Both the rate of polymerization and the degree of polymerization of the polymer also increased with rising temperature. The carboxylic acid added acted as a catalyst in the polymerization because of increase in the polymer yield, the molecular weight of polymer formed, and the number of moles of polymer chain with increasing dissociation constant of acid used. It was concluded that the polymerization in liquid carbon dioxide proceeded by a cationic mechanism. Methyl formate had no influence on the polymerization, but methanol and water acted as a chain-transfer agent.     

121Sb-Mössbauer-Spektren von Antimon(V)-Verbindungen. II

¹²¹Sb Mössbauer Spectra of Antimony (V) Compounds. II The Mössbauer resonance effect of ¹²¹Sb has been studied at 4.2 K in a series of 11 antimony(V) compounds which are in most cases bridged. Isomer shift and quadrupole splitting variations are considered in the light of results of X-ray and vibrational spectroscopy. Preparation and the vibrational spectra of [NMe₄][SbCl₄(n₃)₂] are described. Within the limitations of available structural data related tin compounds are compared with those of corresponding ¹¹⁹Sn Mössbauer spectra.     

Periodic,multiplicative number-theoretical functions

D. Leitmann andD. Wolke [3] proved that multiplicative functions, which are restrictions of continuous, periodic functionsF: with irrational period, are constant equal to 0 or 1. In this note a simpler proof for this result is given.     

A comparison of two approaches to the optimal positioning of a new product in an attribute space

This paper is concerned with the optimal positioning of a new product in an attribute space. A deterministic optimization model that relies on the axiom of choice is compared with the model byShocker/Srinivasan [1974] that incorporates a probabilistic measure of choice. Investigating the assumptions and the construction of both models, it is shown that the probability function byShocker/Srinivasan is based on a controversial assumption and incorporates a parameter that has not been given an economic explanation. Furthermore, both models are applied to complex configurations. It is demonstrated that the optimal positions for the new product resulting from the model byShocker/Srinivasan depend heavily on the parameter just mentioned and may run contrary to plausible consequences of the axiom of choice.

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Zusammenfassung Für die optimale Gestaltung neuer Produkte, d.h. ihrer Positionierung in einem Raum von Produkteigenschaften, wird ein Modell angeboten, das auf einer deterministischen Kaufentscheidung beruht, ein anderes, das eine stochastische Kaufentscheidung unterstellt. Es wird gezeigt, daß der zuletzt genannte Modelltyp stark von der Spezifikation eines ökonomisch bisher nicht erklärten Parameters abhängt und z.T. Konsequenzen aufweist, die dem Wahlaxiom zuwider laufen, auf das das erstgenannte Modell aufbaut. Durch einen Vergleich auch komplexer Konfigurationen von Käuferbeurteilungen neuer Produkte wird gezeigt, welche Gestaltungsentscheidungen auf der Grundlage der beiden Modelle zur Optimierung einer Zielfunktion zu treffen sind.