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101.
102.
Dr. Tohru Takenaka Mr. Yoshiyuki Shimura Prof. Dr. Gotoh Rempei 《Colloid and polymer science》1970,237(1):193-199
Summary In order to obtain informations on the molecular nature and mechanism of rheological processes on polymers, simultaneous measurements of stress and infrared dichroism were made of polychloroprene (Neoprene Type AC) films during the course of continuous elongation at the constant rate 25%/min and of stress relaxation at 400% elongation. The time dependence of the infrared dichroism was obtained by measuring the intensity change at fixed wavenumbers of absorption band maxima on the differential polarized infrared spectra. Both the degree of crystallinity of sample films and the orientation function of transition moments were calculated from the results of the infrared dichroic measurements under the assumption of uniaxial orientation, which was confirmed to be the case by X-ray diffraction and birefringence measurements.In the continuous elongation experiments, it was found that the orientation functions for crystalline-sensitive bands showed maxima at 25% elongation and then decreased rapidly, changing their signs from positive to negative. There also appeared the yield point in the stress-strain curve and the beginning of sharp decrease of crystallinity at the same degree of elongation 25%. These facts were interpreted in terms of the orientation of the crystalline phase followed by the degradation of crystallites and drawing out of the molecular chain from the crystallites. In the stress relaxation experiments, moderate changes in the orientation functions were found for various characteristic absorption bands. Little difference was observed between changes in the orientation functions for the amorphous and crystalline-sensitive bands. This makes a contrast with the previous results for vulcanized natural rubber, where the orientation of the crystalline phase was completed almost immediately after elongation, while in the amorphous phase the molecular chains were oriented gradually during the course of stress relaxation.
With 8 figures in 9 details and 1 table 相似文献
Zusammenfassung Um Informationen über die molekulare Natur und den Mechanismus rheologischer Prozesse von Polymeren zu erhalten, wurden gleichzeitige Messungen der Spannung und des Infrarot-Dichroismus an Polychloropren-Filmen (Typ AC-Neopren) während der kontinuierlichen Verstreckung bei konstanter Verstreckungsgeschwindigkeit von 25%/min und während der Spannungsrelaxation bei 400% Verlängerung durchgeführt. Die Zeitabhängigkeit des Infrarot-Dichroismus wurde aus der Intensitätsänderung im festen Wellenzahlbandmaximum eines Kristallisationsbandes mit einem differenz-polarisierten Infrarot-Spektrographen festgestellt. Beide, der Kristallanteil der Probe und die Orientierungsfunktion für die Übergangsmomente lassen sich aus den Resultaten unter Annahme einachsiger Orientierung auswerten. Letztere, die einachsige Orientierung, wurde mit Röntgenbeugung und Doppelbrechung sichergestellt.In den Experimenten mit kontinuierlicher Verlängerung zeigten die Orientierungsfunktionen der Kristallempfindlichen Banden bei 25% Verlängerung ein Maximum. Danach sanken sie rasch unter Wechsel ihres Vorzeichens von positiv nach negativ ab. Der Fließpunkt in der Spannungs-Dehnungs-Kurve und der Beginn des scharfen Abfalls der Kristallinität zeigen sich vom gleichen Verlängerungsgrad 25% ab.Diese Tatsachen werden aufgrund der Orientierung der kristallinen Phase erklärt, gefolgt von einem Abbau der Kristallite und einem Herausziehen der Molekülketten aus den Kristalliten. In den Spannungsrelaxationsversuchen wurden gewisse Änderungen der Orientierungsfunktionen für die verschiedenen charakteristischen Absorptionsbanden gefunden. Es ergaben sich geringe Differenzen in der Änderung der Orientierungsfunktionen für die amorphen und kristallempfindlichen Banden. Das steht im Gegensatz zu früheren Resultaten an vulkanisiertem Naturkautschuk. Bei letzteren war die Orientierung der Kristallphase beinahe unmittelbar nach der Dehnung vollständig, während in der amorphen Phase die molekularen Ketten nach und nach im Laufe der Spannungsrelaxation orientiert wurden.
With 8 figures in 9 details and 1 table 相似文献
103.
Conflicting pecificities were observed in electro-chemical 2e-reductions of NAD+ analogs: 1-phenyl-3-aminocarbonylpyridiniums gave quantitatively 1,4-dihydronicotinamides whereas 1-benzyl and 1-methyl derivatiives gave 1,6-isomers. 相似文献
104.
Yoshiyuki?KowadaEmail author Toru?Ozeki Tsutomu?Minami 《Journal of Sol-Gel Science and Technology》2005,33(2):175-185
Gel films with various pH indicators were prepared by the sol–gel method without catalysts. The obtained gel films showed good response for various pH solutions as optical pH sensors and no leaching of the indicators was observed. The feature of absorption spectra of the indicators in the gel films was almost the same as that in the aqueous solutions. pKa of the indicators in the gel films was shifted with the increase of the TMOS content in the starting solutions. These results suggest that the pH indicators in the gel films were trapped in similar environment as in the solutions. 相似文献
105.
Tin chlorides, SnCl2 and SnCl4.5H2O are excellent catalysts for the reactions of trioses, dihydroxyacetone and glyceraldehyde with alcohols (MeOH, EtOH and nBuOH) to give alkyl lactates, whose reaction mechanism involves the intermediary formation of pyruvic aldehyde followed by its esterification, which is distinctively promoted by tin halides. 相似文献
106.
The ν(N-H) vibrations of trialkylthioureas observed in the dilute solutions are interpreted in relation to the trans—out isomerism. Occurrence of the out form is discussed from the point of view of steric hindrance. The two forms are characterized by the behavior of ν(N—H) vibrations at several concentrations. Solid DiPTUtB and DcHTUtB exhibited one sharp band at the same position as the ν(N—H) band in solution. This indicates that they are in the out form in the solid state as well as in solution. 相似文献
107.
Yoshiyuki Kitaoka 《Journal of Number Theory》1980,12(2):224-229
Let L be a positive Z-lattice with level N = cd, (c, d) = 1. Then the Fourier expansion at cusp of the theta function associated to L is a theta function associated to L1, where a lattice L1 is defined by ZpL1 = ZpL for , ZpL1 = the dual of ZpL for p | c. 相似文献
108.
Observations of the direct l-type resonance transitions in the microwave spectrum of the v6 = 1 state of CHF3 and CDF3 have been extended to J = 37. Accidental degeneracies were found between J = 34, in both molecules enabling the C rotational constants of CHF3 and CDF3 to be determined, using 118 observed frequencies for CHF3 and 104 for CDF3. After suitable correction the B and C rotational constants were used to determine the r0, r2, and re structures for CHF3 and CDF3.The equilibrium structure was determined to be , and ∠FCF = 108.58 ± 0.34°. 相似文献
109.
Shoji M Kato E Nakamura Y Fujii T Manabe Y Ueda M 《Chemical record (New York, N.Y.)》2006,6(6):344-355
The chemical aspects of the circadian leaf movement known as "nyctinasty" are discussed in this paper. Each of the nyctinastic plants of five different genera so far examined contained a pair of factors, one of which induced leaf closure and another induced leaf opening. The relative contents of the closing and opening factors changed correlating with the nyctinastic leaf movement. The use of fluorescence-labeled and photoaffinity-labeled factors revealed that the factors bind to specific cells, the motor cells, present in the pulvini, and that the membrane fraction of the motor cells contained two proteins of 210 and 180 kDa, which can bind to the factors. 相似文献
110.
Hisakazu OGITA Yoshiyuki RIKITAKE Jun MIYOSHI Yoshimi TAKAI 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2010,86(6):621-629
Nectins have recently been identified as new cell adhesion molecules (CAMs) consisting of four members. They show immunoglobulin-like structures and exclusively localize at adherens junctions (AJs) between two neighboring cells. During the formation of cell–cell junctions, nectins function in cooperation with or independently of cadherins, major CAMs at AJs. Similar to cadherins, which are linked to the actin cytoskeleton by binding to catenins, nectins also bind to afadin through their C-terminal region and are linked to the actin cytoskeleton. In addition to nectins, there are nectin-like molecules (Necls), which resemble nectins in their structures and consist of five members. Nectins and Necls are involved in the formation of various kinds of cell–cell adhesion, and also play key roles in diverse cellular functions including cell movement, proliferation, survival, and differentiation. Thus, nectins and Necls are crucial for physiology and pathology of multicellular organisms. 相似文献