Dielectric behavior of polyethyleneoxide (polyox)

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Isolation,chemical characterization and structure of ansamitocin,a new antitumor ansamycin antibiotic

In this paper we report the isolation, chemical characterization and structural elucidation of Ansamitocin, a new antitumor antibiotic obtained from Nocardia No. C-15003 (N-1). Ansamitocin P-3, P-3' and P-4 with molecular formulae C₃₂H₄₃ClN₂O₉, C₃₂H₄₃ClN₂O₉ and C₃₃H₄₅ClN₂O₉, respectively, were identified as novel antibiotics. Their UV spectra resemble that of maytansine obtained from a plant source. Analysis of the PMR spectrum and spin-decoup studies of P-3 demonstrated that its skeletal structure was the same as that of maytansine. Reductive cleavage of each antibiotic gave maytansinol (P-0). Alkali hydrolysis of P-3, P-3' and P-4 gave isobutyric, butyric and isovaleric acids, respectively. P-3, P-3' and P-4 were concluded to be the isobutyrate, butyrate and isovalerate ester of maytansinol at C-3, respectively. An antitumor plant product, maytanacine, and its semisynthetic derivative, maytansinol propionate, were also produced by the same strain.     

Formation of kink bands by compression of the extrudate of solid linear polyethylene

Extrudates of solid linear polyethylene prepared under proper pressure and temperature conditions have a high c axis orientation along the extrusion direction, with lamellar crystals and amorphous layers stacked alternately along the extrusion direction. Kink bands were formed by compressing the oriented extrudate at room temperature along the extrusion direction. Inspection of the kink bands by wide-angle and small-angle x-ray diffraction and electron microscopy revealed that the fiber axis was rotated from the original axis direction by 70–75° and that the lamellar crystals were inclined to the fiber axis in the kink band by 55–60° and stacked nearly parallel to the kink boundary. The superstructural change during the formation of the kink band could not be interpreted in terms of uniform c axis shear alone. In addition to such a mechanism, it was necessary to take into account intermicrofibril and/or intercrystallite slip.     

ESR study of radical sites in crystalline texture of irradiated polypropylene by means of nitric acid etching

Bulk-crystallized isotactic polypropylene samples with different crystalline textures were etched by fuming nitric acid to remove the disordered region. The radicals produced by irradiation of γ-rays or ultraviolet light on these etched samples in vacuum at liquid nitrogen temperature were investigated by the ESR method. A triplet spectrum in addition to the original spectrum of polypropylene radicals was separated for the etched samples. It was concluded that this triplet was caused by radical species associated with nitro groups introduced on the surface of the crystalline residues by etching. The difference in the intensity of this triplet among the samples was ascribed to differences in crystalline textures and interpreted in a quantitative way. The concentration of polypropylene radicals corrected for the triplet differed among the quenched, annealed, and cold-drawn samples and the sample annealed one after drawing. This fact was interpreted on the basis of the hypothesis that radical sites were almost concentrated in the defects of crystal domain. The well known nonet spectrum, which can be observed at liquid nitrogen temperature after annealing the irradiated samples at room temperature, was also confirmed to be attributable to the defects of crystals. The behavior of free methyl radicals induced by ultraviolet irradiation was also found to be strongly dependent on the state of aggregation of the polymer molecules.     

Radical formation during tensile deformation of highly drawn crystalline poly[p-(2-hydroxyethoxy)benzoic acid] fibers

The micromechanism of tensile deformation of poly[p-(2-hydroxyethoxy)benzoic acid] fibers is discussed on the basis of a detailed esr study of radical formation. The concentration of primary phenoxy radicals, which were detected during deformation at room temperature as a direct indicator of main-chain rupture, was determined by extrapolating the radical decay curves at various strains to zero time. The relation between the initial radical concentration and the strain is well expressed by the cumulative normal distribution curve. By use of this relation and a model of fiber structure, the distribution of the contour length of tie chains was determined. No radicals were detected during a second stretching cycle until the maximum strain in the first run was exceeded. The deformation model which includes alternating crystalline and amorphous regions connected by tie chains, a distribution of contour lengths of tie chains, and a phase transformation of molecular chains in the crystalline region accounted fairly well for the observed stress–strain behavior of monofilaments in first and second stretching cycles. The comparison between the observed and the calculated radical concentration suggests that statistical factors and other deformation mechanisms have to be taken into account.     

Dielectric properties of poly [3,3-bis(chloromethyl)oxacyclobutane] (Penton)

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Effects of degree of crystallinity upon dielectric behaviors in some aromatic Polyesters

Zusammenfassung An vier polymerhomologen Reihen von Oligomeren des Nylon 6-, Nylon 66- und Polyurethantyps wurde der Einfluß einer Temperaturvorbehandlung, der Phenolquellung und der Kristallisationsbedingungen auf die Langperiode röntgenographisch untersucht. Es wurde der Polymerisationsgrad festgestellt, bei dem die Oligomeren der vier Reihen erstmalig moleküllängenunabhängige Langperioden nach Art der vonHeß undKießig in Röntgenogrammen von Polyamiden und Polyestern entdeckten Kleinwinkelinterferenzen liefern.Das Auftreten vonHeß-Kießig-Reflexen in denKratky-Diagrammen der höheren Oligomeren wird durch Kettenüberfaltung erklärt.XXVII. Mitt. über Oligomere. XXVI. Mitt. vgl.Zahn, H., J. Kunde undG. Heidemann, Makromol. Chem.43, 220 (1961).Dem Andenken anKurt Heß gewidmet.Wir danken dem Bundeswirtschaftsministerium (Forschungsvorhaben J 272), dem Fonds der Chemischen Industrie, Düsseldorf, sowie der Deutschen Forschungsgemeinschaft, Bad Godesberg, für die Förderung dieser Arbeit.     

Studies on dielectric properties of polyvinylidene chloride

Colloid and Polymer Science - The ?′ and ?″ for polyvinylidene chloride investigated were measured at frequencies from 100 c/s to 2 M c/s, at various fixed temperatures from...