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  • Polymer and Materials Science  (187)
  • SPACE RADIATION  (53)
  • Organic Chemistry
  • 1970-1974  (178)
  • 1960-1964  (77)
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  • 1
    Digitale Medien
    Digitale Medien
    Spectres de résonance paramagnétique électronique des catalyseurs de polymérisation à base de TiCl3. II. Etude théoriqueDédié à Monsieur le Professeur CH. SADRON à l'occasion de son 70me anniversaire. (1972)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 162 (1972), S. 135-146 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Aus der Analyse des E.S.R.-Spektrums einer Probe von Titantrichlorid (Stauffer H) resultieren fünf Elementarsignale, von denen drei 85% des ganzen Spektrums darstellen und eine axiale Symmetrie aufzeigen. Mit Hilfe der Ligandenfeldtheorie und den Ergebnissen der diffusen Reflexion im ultravioletten und sichtbaren Bereich gelangt man zu dem Schluß, daß diese Signale aus inneren Kristallstruktur-Fehlern stammen. Diese Schlußfolgerung stimmt mit verschiedenen experimentellen Beobachtungen überein.
    Notizen: Le spectre de résonance paramagnétique électronique d'un échantillon de TiCl3 (Stauffer H) est analysé comme la somme de cinq signaux élémentaires dont trois représentent 85% du total et présentent une symétrie axiale. A l'aide de la théorie du champ cristallin et des résultats d'une étude spectroscopique UV-visible en réflexion diffuse, on arrive à conclure que ces signaux proviennent de défauts internes de la structure cristalline; cette conclusion est en accord avec plusieurs observations expérimentales.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1972.021620113
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  • 2
    Digitale Medien
    Digitale Medien
    Induced optical activity in poly-L-lysine-methyl orange system (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2423-2430 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The absorption and cicular dichroism spectra of the complex of poly-L-lysine (PLL) in the random coil form with methyl orange (MO) have been measured in aqueous solution. A new absorption band is observed at the shorter wavelength compared with that of the free dye. Although MO does not show a formation of dimer or aggregation with an increase in concentration, circular dichroism bands are observed at the wavelength corresponding to the wavelength of the new absorption band. These induced circular dichroism bands may arise from the dimeric MO molecules bound to PLL in the random coil form. The main contribution to the interaction between MO molecules is shown to be the electro static interaction. The observed circular dichroism spectra and the configuration of dimeric MO molecules bound to PLL can be explained by the dipole couping mechanism.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1973.360121019
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  • 3
    Digitale Medien
    Digitale Medien
    Stereospecific bulk polymerization of methyl methacrylate initiated by its tactic polymers (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 989-1001 
    Details
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Methyl methacrylate (MMA) was polymerized by radical initiation at 90°C by its own preformed tactic polymers, i.e., conventional (c-PMMA), isotactic (i-PMMA), and syndiotactic (s-PMMA) PMMA, and also by a preformed 1:1 stereocomplex of i-PMMA and s-PMMA. The collected polymers were separated into two fractions by extraction with boiling acetone and characterized by 60 MHz NMR spectra and viscometry. Higher polymerization rates were obtained in the presence of stereo-regular PMMA than in the presence of c-PMMA. Moreover, it appeared that i-PMMA promoted the formation of s-PMMA, and conversely s-PMMA the formation of i-PMMA, especially in the initial stages of the reaction. A higher M̄v of the preformed polymer yielded a higher rate and a higher stereospecificity of the polymerization. No polymerization took place in the absence of performed PMMA. The results support a replica mechanism proposed by Szwarc, in which polymerization is preceded by a specific arrangement of monomeric units along the polymeric chain into a distinctive pattern. Such arrangement coupled with a strong tendency of the isotactic and syndiotactic species to associate may lead to the present stereospecific replica polymerization. This association is demonstrated by rapid gelation during polymerization and by lowering of reduced viscosity in very dilute mixtures of i-PMMA and s-PMMA in MMA.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1973.170110506
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  • 4
    Digitale Medien
    Digitale Medien
    Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). IV. Influence of solvent type (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 2975-2989 
    Details
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Methyl methacrylate (MMA) was polymerized by radical initiation at 25°C or 35°C in various solvents in the presence of stereoregular poly(methyl methacrylate) (PMMA). The occurrence of stereospecific replica polymerization appeared to be related to the capability of stereoassociation of isotactic and syndiotactic PMMA. The solvents can be roughly divided into three types. Type A solvents are polar solvents, which promote stereoassociation resulting in gelation and precipitation. Examples are dimethylformamide, dimethyl sulfoxide, and acetone. Type B solvents are nonpolar aromatic solvents like benzene and toluene, wherein stereoassociation is weaker but still leads to gelation. Type C solvents are very good solvents, in which stereoassociation does not occur. Chloroform and dichloromethane belong to this class. In solvents of type A as well as type B, polymerization in the presence of i-PMMA as a polymer matrix was syndiospecific. However, in the presence of s-PMMA as a polymer matrix the polymerization was isospecific only in type A solvents. The syndiotactic or isotactic triad contents of the polymer formed could be as high as ca. 90% at low conversions. In solvents of type C, polymerization in the presence of stereoregular PMMA proceeds according to a normal radical mechanism. Syndiotacticity was always less than 70%. Stereocomplexes formed in situ during replica polymerization were partly crystalline as detected by x-ray diffraction. The highest crystallinity was detected in those formed in type A solvents.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1973.170111116
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  • 5
    Digitale Medien
    Digitale Medien
    Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). II. Syndiotactic PMMA as matrix (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 1003-1011 
    Details
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Methyl methacrylate (MMA) was polymerized by radical initiation at 25°C in DMF in the presence of preformed syndiotactic PMMA (sMA) with about 90% syndiotactic triads and of different M̄v, viz., sMA-1, 1.6 × 105; sMA-2, 3.0 × 105; and sMA-3, 8.7 × 105. The MMA:sMA ratio was 6:1. The collected polymers were separated into two fractions by extraction with boiling acetone and characterized by 60 MHz NMR. In all cases isotactic PMMA (i-PMMA) was produced, especially in the initial reaction stages, which associated with the syndiotactic substrate to form acetone-insoluble 1:2 i/s-stereocomplexes. The isotacticity decreased with conversion and was highest in the presence of sMA-3. Characterization of the acetone-soluble fractions indicated that i,s-stereoblock polymers were also produced. From these results it is concluded that this reaction can be considered a stereospecific replica polymerization, the driving force being the strong tendency of i-PMMA and s-PMMA to associate. With sMA of M̄v below about 1.2 × 105, no i-PMMA is formed; in other words, no replica polymerization occurs. For polymerizations in the presence of sMA-2, the critical M̄v of propagating chains, with has to be exceeded before stereoassociation is strong enough to effectuate replica polymerization, has been estimated to be 0.6 × 105.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1973.170110507
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  • 6
    Digitale Medien
    Digitale Medien
    Chemical structure of poly(vinyl alcohol)/methyl methacrylate graft copolymers prepared by various methods (1970)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 139 (1970), S. 183-196 
    Details
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Pfropfcopolymere aus Polyvinylalkohol (PVA) mit Methylmethacrylat (MMA) wurden durch direkte Bestrahlung, Vorbestrahlung und nach der katalytischen Methode mit Kaliumpersulfat hergestellt; außerdem wurde eine Methode verwendet, die keine Katalysatoren benötigt.Nachdem die reinen Pfropfcopolymeren von unaufgepfropften PVA und Homo-PMMA durch erschöpfende, wechselseitige Extraktion isoliert worden waren, wurden die Hydroxylgruppen in den Copolymeren quantitativ acetyliert, damit einerseits osmotische Messungen möglich wurden und andererseits die Zusammensetzung durch hydrolytischen Abbau bestimmt werden konnte. In einem anderen Versuch wurden die aufgepfropften Seitenketten durch oxydative Spaltung der 1.2-Glykol-Bindungen im PVA-Molekül mit Perjodsäure isoliert, und das Molekulargewicht wurde osmometrisch bestimmt. An Hand dieser Ergebnisse wird gezeigt, daß die gebildeten Pfropfcopolymeren aus nur einer Seitenkette und einem Ausgangs-PVA-Molekül bestehen und daß ihre Struktur von den verwendeten Aufpfropfungsmethoden unabhängig ist.
    Notizen: Poly(vinyl alcohol) (PVA)/methyl methacrylate (MMA) graft copolymers were prepared by mutual irradiation, pre-irradiation, and by a catalytic method with potassium persulfate (KPS); a technique to prepare graft copolymer using no initiator was also adopted. After pure graft copolymers were isolated from the graft films by vigorous alternate extraction unreacted PVA and homo-PMMA, hydroxyl groups in the copolymers were completely acetylated to carry out osmotic pressure measurements and determine the chemical composition by hydrolysis. Graft branches were separated by cleaving C—C bonds of 1.2-glycol structure in backbone PVA with periodic acid. The chemical structure of the graft copolymers was made clear on the basis of the measured number-average molecular weights of the pure graft copolymer, separated branch and mother PVA molecule, and the chemical composition of the graft copolymer. It was shown that the graft copolymer has only one branch and one mother PVA molecule, irrespective of the grafting methods employed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1970.021390114
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  • 7
    Digitale Medien
    Digitale Medien
    Reactive polypeptides I synthesis of poly-γ-cinnamyl-L-glutamate (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 12 (1974), S. 715-718 
    Details
    ISSN: 0360-6384
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1974.130121208
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  • 8
    Digitale Medien
    Digitale Medien
    Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). III. Influence of temperature (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 1013-1024 
    Details
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Methyl methacrylate (MMA) was polymerized by radical initiation at 0, 25, 50, 75 and 100°C in DMF in the presence of preformed isotactic PMMA (iMA) or preformed syndiotactic PMMA (sMA) with different M̄v and also without preformed PMMA (“blank” polymerizations). From the tacticities of the formed polymers it is concluded that blank polymerization does not conform to simple Bernoulli statistics, but follows at least first-order Markov statistics. The formation of long syndiotactic sequences in the presence of iMA and long isotactic sequences in the presence of sMA denotes still higher-order Markov statistics. The stereoregulating action is improved by higher M̄v of the preformed polymer (matrix) and lower reaction temperature. These influences can be explained by assuming an equilibrium between polymer growth on the matrix and in the “free” solution. For polymerizations in the presence of iMA or sMA below 300°K, the differences in activation enthalpies (ΔHs/i
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1973.170110508
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  • 9
    Digitale Medien
    Digitale Medien
    Radical polymerization of methyl methacrylate in the presence of isotactic poly(methyl methacrylate) (1972)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 10 (1972), S. 1031-1049 
    Details
    ISSN: 0449-296X
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Methyl methacrylate (MMA) was polymerized by radical initiation at 25°C in DMF in the presence of preformed isotactic PMMA (iMA) with about 90% isotactic triads and different M̄v's, viz., iMA-1: 7.2 × 105; iMA-2, 5.0 × 105; iMA-3, 3.5 × 105; iMA-4, 1.25 × 105; and iMA-5, 1.15 × 105. The MMA:iMA ratio was 6:1. The collected polymers were separated into two fractions by extraction with boiling acetone and characterized by 60 MHz NMR. It is found that the M̄v of the polymer formed ran parallel to the M̄v of iMA. In all cases syndiotactic PMMA (s-PMMA) was produced which associated with the isotactic substrate to form acetone-insoluble stereocomplexes. The syndiotactic polymers probably consist of long syndiotactic and heterotactic sequences. The syndiotacticity decreased with conversion and was generally highest in the presence of iMA-1. With iMA-1 even the formation of some additional i-PMMA (in the acetone-insolubles) was indicated, especially in the later stages of the polymerization. Characterization of the acetone-soluble fractions indicated that i,s-stereoblock polymers were also produced, of which the persistence ratios ρ increased with the M̄v of iMA. From these results it is concluded that this reaction differs from the conventional radical polymerization and can be considered a stereospecific replica polymerization, the driving force being the strong tendency of i- and s-PMMA to associate. The formation of i,s-stereoblock polymers and additional i-PMMA indicates that s-PMMA in its turn can also act as a polymer matrix.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1972.150100408
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  • 10
    Digitale Medien
    Digitale Medien
    Calorimetric measurement of enthalpy change in the isothermal helix-coil transition of poly-L-lysine in aqueous solution (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 657-680 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The heat ΔH° for converting an uncharged lysine residue from a coil to an α-helical state in poly-L-lysine in 0.1N KCl has been determined calorimetrically to be -1200 cal/mole at both 15°C and 25°C. Essentially the same value has been obtained for the conversion of an uncharged residue from a coil to a β-pleated sheet state. Titration data provided information about the state of charge of the polymer in the calorimetric experiments, and optical rotatory dispersion data about its conformation. In order to compute ΔH°, the observed Calorimetric heat was corrected for the heat of breaking the sample cell, the heal of dilution of HCl, the heat of neutralization of OH- ion, and the heat of ionization of the ε-amino group in the random coil. The latter was obtained from similar Calorimetric measurements on poly-D,L-lysine, which was shown to be a good model for the random coil form of poly-L-lysine. The measured transition heat was ∼0.7 cal., which is only 7% of the total heat liberated when a 40 ml solution of 0.25% w/v poly-L-lysine is brought, from pH 11 to pH 7; nevertheless it could be determined with a precision of ±8%. The conformation of poly-L-lysine at pH 11 appears to be completely helical at 15°C, but a mixture of 90% α-helix, 5% β form, and 5% coil at 25°C. Since ΔH° ∼ 0 for the α ⇌ β conversion, the polymer behaves like one of 95% α-helix and 5% coil in the calorimeter at 25°C. At neutral pH, poly-L-lysine is an extended coil, like poly-D,L-lysine.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360100406
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