Untersuchungen zur 3-Phononenabsorption in partiell kristallinen Polymeren

Zusammenfassung In dieser Arbeit wird die Dreiphononenabsorption in Polymeren, die den Hauptanteil an den dielektrischen Verlusten im Millimeterwellengebiet stellt, theoretisch und experimentell untersucht. Aus der Störungsrechnung bis zur 2. Ordnung wird die Temperaturabhängigkeit der Absorption abgeschätzt. Damit ist eine befriedigende Deutung des gesamten Temperaturverlaufs der dielektrischen Verlust-Kurven möglich. Im Hochtemperaturbereich läßt sich die Mehrphononenabsorption eindeutig gegenüber restlichen Relaxationsprozessen abgrenzen. Im Tieftemperaturgebiet konnte erstmals auch für das Millimeterwellengebiet ein temperaturunabhängiger Bestandteil fehlordnungsinduzierter Einphononenabsorption nachgewiesen werden. Im Übergangsbereich durchlaufen die Absorptionskurven einen Wendepunkt bei einer charakteristischen TemperaturT ₀, die dem Schwerpunkt der am Absorptionsprozeß beteiligten Phononenfrequenzen entspricht. Daraus konnten in Übereinstimmung mit dem Experiment die Frequenzen der niedrigsten optisch aktiven Phononen für die verschiedenen Polymeren abgeschätzt werden.

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Summary The 3-phonon absorption in polymers, which gives the main contribution to their dielectric loss in the microwave region, is theoretically and experimentally investigated. Perturbation theory up to the second order is used for the evaluation of its temperature dependence. The theoretical results allow an interpretation of the total absorption-temperature-curves: In the high temperature region 3-phonon absorption can be distinguished from residual relaxation losses (above the glass temperature). In the low temperature region the existence of a low frequency tail of temperature independent disorderinduced one-phonon absorption became evident. At intermediate temperatures (50–150°K) the curves show an inflexion point or plateau at a characteristic temperatureT ₀, which according toT ₀= ⁰, corresponds to the frequencies of those phonons, that mainly contribute to the multiphonon absorption. The plateau gives, in good agreement with the experiment, the frequencies of the lowest optically active phonons in the various polymers.

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Mit 6 Abbildungen in 8 Einzeldarstellungen

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Vorgetragen auf der Arbeitssitzung des Fachausschusses Physik der Hochpolymeren in der Frühjahrstagung 1970 des Regionalverbandes Hessen-Mittelrhein-Saar der Deutschen Physikalischen Gesellschaft in Darmstadt, 10.–13. März 1970.     

Investigations of benzimidazole derivatives

3-(1-Methyl-2-benzimidazolyl)acrylic acid was obtained by the reaction of 1,2-dimethylbenzimidazole with chloral and subsequent hydrolysis of the condensation product. The hydrochloride of the chloride of this acid and its esters and amides were synthesized. The methyl and ethyl esters of the acid were synthesized by the Wittig reaction. The IR and UV spectra of the compounds obtained are presented.See [9] for Communication XXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1566–1568, November, 1970.     

Structure des savons alcalins

Summary This is a systematic X-ray diffraction study of the structure of the mesomorphic phases occurring with potassium soaps ranging from C₈ to C₂₂.Four types of structure have been identified. The first is lamellar with both polar groups and paraffin chains in the crystalline state. The second is also lamellar, but with both polar groups and paraffin chains in the liquid state. The third corresponds to the localization of indefinitely long ribbons on a two-dimensional oblique lattice; polar groups are crystalline and paraffin chains desorganized. The fourth corresponds to the localization of discs on a three-dimensionnalB-faces centered orthorhombic lattice; polar groups are crystalline and paraffin chains disorganized.The structural parameters and the polymorphism of the polar groups have been discussed.

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Zusammenfassung Wir beschreiben hier eine systematische Röntgenstrahlendiffraktionsforschung der Struktur der mesomorphen Phasen von Kalium Seifen von C₈ bis C₂₂.Vier Strukturtypen wurden gefunden. Die erste Struktur ist lamellar; beides, die polaren Gruppen und die Paraffinketten sind kristallisiert. Die zweite Struktur ist auch lamellar; aber in diesem Falle sind beides, die polaren Gruppen und Paraffinketten geschmolzen. Die dritte Struktur entspricht einer Lokalisation von Seifenbändern in einem zweidimensionalen monoklinen Gitter; die polaren Gruppen sind kristallisiert und die Paraffinketten geschmolzen. Die vierte Struktur entspricht einer Lokalisation von Seifenscheiben in einemB-flächenzentrierten orthorhombischen Raumgitter; die Polargruppen sind kristallisiert und die Paraffinketten geschmolzen.Wir haben aus den experimentellen Resultaten einige Schlußfolgerungen gezogen.

     

Synthesis and Structure of the New Ammonium Indium Phosphate (NH4)In(OH)PO4

A new ammonium indium phosphate (NH₄)In(OH)PO₄ was prepared by hydrothermal reaction in the In₂O₃-NH₄H₂PO₄-NH₃/OH system (T=200°C, autogenous pressure, 7 days). The formula (NH₄)In(OH)PO₄ was determined on the basis of chemical and thermal analysis (TG/DSC), X-ray powder diffraction and IR-spectroscopy. (NH₄)In(OH)PO₄ crystallizes in the tetragonal system with space group P4₃2₁2 (No. 96); a=9.4232(1) Å, c=11.1766(1) Å, V=992.45(2) ų; Z=8. The crystal structure was refined by the Rietveld method (R_w=6.35%, R_p=5.10%). The second-harmonic generation study confirmed that structure of (NH₄)In(OH)PO₄ does not have a center of symmetry. The cis-InO₄(OH)₂ octahedra form helical chains, parallel to the c-axis. The In-O-In bonds are nearly equidistant. The chains are interconnected by phosphate tetrahedra and create tunnels containing the NH₄⁺ ions along the c-axis. (NH₄)In(OH)PO₄ is isostructural with RbIn(OH)PO₄.     

Ion-exchange properties of silica gel with covalently bonded histidine

The ion-exchange and acid-base properties of Silasorb 600 (10 μm) with immobilized histidine (His-SiO₂) were investigated. The acid-base properties of the sorbent were estimated from the dependence sof the retention of organic acids and bases on the eluent pH. The effect of various organic modifiers (benzoic, citric, oxalic, and sulfuric acids) and the eluent pH on the retention of inorganic ions was studied. It was shown that His-SiO₂ exhibits anion-exchange properties in acidic and weakly acidic media at pH < 5.7. Eight anions were separated under optimal conditions on a 150 × 4.6-mm column in 21 min using a 5 mM oxialic acid solution as an eluent.     

Quantitative estimation of the α-effect in the reactions yielding phosphorus-containing thiosemicarbazides

The α-effect in the reactions of O,O-diaryl phosphorohydrazidothioates with phenyl isothiocyanate in benzene at 25°C was quantitatively evaluated from the kinetic data. The probable reaction mechanism was suggested, and the causes of the α-effect in these reactions are discussed. An approximate linear correlation is observed between the α-effect in the reactions of O,O-diaryl phosphorohydrazidothioates with phenyl isothiocyanate, basicity constants of the hydrazides, and σ^p constants of the substituents at the P atom. The value of the α-effect is largely determined by the structure of the transition state.     

Isoscalar factors for tetragonal,orthorhombic, monoclinic and triclinic shubnikov point groups

The relations between isoscalar factors for corepresentations of antiunitary magnetic point groups are discussed in the case of associated corepresentations. The tables of the isoscalar factors for the single- and double-valued corepresentations of all tetragonal, orthorhombic, monoclinic, and triclinic Shubnikov point groups are given. Some peculiarities of the calculation method of the isoscalar factors for corepresentations are considered.     

Synthesis and properties of N-methylmorpholinium 4aryl-6-methyl-5-phenylcarbamoyl-3cyano-1,4dihydropyridine-2-thiolates. Molecular and crystalline structure of 2allylthio-6-methyl-5-phenylcarbamoyl-4-(2chlorophenyl)-3-cyano-1,4-dihydropyridine

By the condensation of an aromatic aldehyde, the anilide of acetoacetic acid, cyanothioacetamide, and Nmethylmorpholine, substituted N-methylmorpholinium 1,4-dihydropyridine-2-thiolates have been synthesized and subsequently used in the synthesis of the corresponding thiones, 2-alkylthiopyridines, thieno[2, 3b]pyridines, and disulfides. X-ray diffraction has been used to establish the structure of 2-allylthio-6-methyl-5phenylcarbamoyl-4-(2-chlorophenyl)-3-cyano-1, 4-dihydropyridine.T. G. Shevchenko Lugansk State Pedagogical Institute, Lugansk 348011. A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, Moscow 117813. N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1243–1251, September, 1996. Original article submitted May 13, 1996.     

Effect of modified fibre glass on the structure and thermophysical properties of pentaplast(pentane)

The results of experimental investigations of the effects of ground fibre glass on the structural parameters and thermophysical characteristics of pentaplast(pentane) were assessed.The degree of crystallinity, thermal conductivity, specific heat and density of pentaplast containing various amounts of modified fibre glass were determined experimentally.The results obtained are discussed in terms of modern theories of the effects of fillers on the properties and structures of polymers.

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Zusammenfassung Es werden die Ergebnisse der experimentellen Untersuchungen des Einfl usses von gemahlenem Fiberglas auf die Strukturparameter und thermophysikalischen Eigenschaften von Pentaplast (Pentan) gewertet.Der Kristallinitätsgrad, das Wärmeleitvermögen, die spezifische Wärme und die Dichte von Pentaplast mit verschiedenem Gehalt an modifiziertem Fiberglas wurde experimentell ermittelt.Die erhaltenen Ergebnisse wurden hinsichtlich moderner Theorien über den Einfluß von Streckmitteln auf die Eigenschaften und die Struktur von Polymeren diskutiert.

     

13C-NMR. Spectroscopy of naturally occurring substances. XXXII. Vincaleucoblastine and related alkaloids.

The total assignment of the ¹³C-shifts of the complex Vinica rosea L. alkaloids vincaleucoblastine, leurosidine and leurosine and of a synthetic isomer of the latter is presented. The structure of leurosidine is corrected and a tentative structure for the acid-catalyzed product of isomerization of leurosine is proposed.