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  • 1
    ISSN: 1520-4804
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary We focused on the stage preceding the thermally-induced phase separation of aqueous solution of poly(ethoxyethyl vinyl ether) (PEVE). Previously, we observed an interesting dynamic quenching just below the phase separation temperature. The dynamic fluorescence quenching disappeared by addition of a surfactant. In systems without the phase separation of both the hexane solution of PEVE and the PEVE bulk, the fluorescence lifetime decreased monotonically with the increase of temperature. These results indicated that the marked decrease is due to the dynamic quenching by the collision between the fluorescent probe and the PEVE segment induced by the thermal fluctuation precedent to the phase separation.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Polymer bulletin 3 (1980), S. 285-290 
    ISSN: 1436-2449
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Summary Asymmetric induction copolymerization and Diels-Alder reaction were investigated between acrylic monomer and olefin or diolefin with use of an optically active aluminum compound as the complexing agent. In the copolymerization, only benzofuran gave an optically active alternating copolymer, while butadiene and indene gave alternating copolymers but with no optical activity. EtAlCl2-l-menthol was the most effective complexing agent. However, EtAlCl2-d-neomenthol was ineffective. On the other hand, Diels-Alder reaction was in general more easily stereocontrolled. For instance, both complexing agents were effective for the synthesis of optically active Diels-Alder adducts with butadiene or cyclopentadiene, perhaps due to the rigid cyclic structure in a transition state of the reaction.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 175 (1974), S. 237-245 
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die protonenentkoppelten 13C-Kernresonanzspektren (natürliche Isotopenhäufigkeit) des äquibinären (cis-1,4 - 1,2)-Polybutadiens wurden gemessen. Alle Resonanzen im aliphatischen Bereich wurden zugeordnet; hierbei wurden geschätzte Korrekturterme für die chemischen Verschiebungen im vorliegenden System zusammen mit den GRANTschen Parametern verwendet. Für jeden Peak wurde außerdem angegeben, ob er zu einer Diade oder Triade von cis-1,4- und 1,2-Einheiten gehört. Die gemessenen relativen Intensitäten der Peaks stimmten mit den berechneten Intensitäten überein; der Rechnung wurde eine regellose Verteilung der cis-1,4- und der 1,2-Einheiten zugrunde gelegt. Die gaschromatographische Analyse der Ozonolyseprodukte der Polymere zeigte ebenfalls eine regellose Verteilung der beiden Einheiten an.
    Notizen: The proton decoupled natural abundant 13C-NMR spectra of equibinary (cis-1,4 - 1,2)-polybutadiene were measured. Assignments of spectra were made for all peaks of the aliphatic range using chemical shift corrective terms estimated for the present system together with GRANT's parameters. Each peak was interpreted in terms of the diad or triad of cis-1,4 and 1,2 units. The relative intensities of the peaks were in good agreement with the calculated ones from the random assumption with respect to the distribution of cis-1,4 and 1,2 units. The gas-chromatographic analysis of the ozonolysis product of the polymers also showed that the sequence distribution of cis-1,4 and 1,2 units was random.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A novel addition polymerization of 1,4-diethynylbenzene (1) with 1,4-benzenedithiol (2) was studied under UV-irradiation in toluene solution at -20°C. The addition polymerization was found to proceed rapidly and a pale-yellowish polymer precipitated with the progress of the reaction (M̄n = 7500). A soluble polymer was recovered from the toluene solution by evaporation. Its M̄n value was estimated to be 3000. When an excess amount of 2 was used (mole ratio 1:2 = 2:3), the yield of the insoluble polymer increased. TG of the polymer indicated its decomposition point to be ≈500°C in air. The electroconductivity of the insoluble and soluble polymers was found to be 10-2 S · cm-1 and 10-5 S · cm-1 when doped with I2 at room temperature, respectively, and the conductivity was reversibly increased with increasing temperature up to 90°C. At T 〉 90°C the iodine was released and the conductivity decreased.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The living cationic polymerization of isobutyl vinyl ether (IBVE) with 1-(isobutoxy)ethyl acetate (1)/C2H5AlCl2 as initiating system in hexane at +40°C in the presence of carboxylates was investigated in regard to the effect of the basicity and the steric hindrance of the added esters on the rate and living nature of the polymerization. The effect of the basicity was evaluated by use of four p-substituted ethyl benzoates (X—C6H4—COOC2H5; X: CH3O, CH3, H, Cl). Despite of the difference in basicity, all the benzoates gave living polymers with narrow molecular-weight distributions (ratios of weight- to number-average molecular weights Mw/Mn ≤ 1,1), whereas the polymerization rate depends on the p-substituents as follows: CH3O 〈 CH3 〈 H 〈 Cl. Another series of experiments showed that the steric environment around the carbonyl group also affects the polymerization rate. Namely, using carboxylates with various carbonyl substituents (R—COOCH3; R: CH3, C2H5, (CH3)2CH, (CH3)3C), the polymerization rate increases with increasing bulkiness of the substituent R in the order: (CH3)3C 〉 (CH3)2CH 〉 C2H5 〉 CH3. These electronic and steric effects are consistent with the stabilization of the carbocation by the nucleophilic interaction of added bases. Fast living polymerization of IBVE can be obtained using the initiating system 1/C2H5AlCl2 in the presence of methyl chloroacetate, an ester with a strongly electron-withdrawing group.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 1759-1768 
    ISSN: 0025-116X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Fast living cationic polymerization of isobutyl vinyl ether (IBVE) was examined using the initiating system 1-(isobutoxy)ethyl acetate (1)/C2H5AlCl2 in the presence of various esters in hexane between 0°C and +40°C. Methyl chloroacetate as added ester turned out to be effective: the apparent polymerization rate constant k was larger by a factor of 400 - 500 than that in the presence of methyl acetate. The rate difference was explained on the basis of the basicity of the esters and their nucleophilic interaction with the propagating species. The polymers obtained in the presence of both esters had a narrow molecular-weight distribution (MWD) (Mw/Mn ≤ 1,1), and Mn was directly proportional to monomer conversion. As low reactive monomers, 2-chloroethyl vinyl ether (CEVE) and tert-butyldimethylsilyl vinyl ether (SiVE) were polymerized under similar conditions. By selecting methyl chloroacetate as an additive, in the case of CEVE, fast living polymerization was achieved to give quantitative conversion within 10 min at 0°C; in the case of SiVE, polymers with a narrow MWD were obtained even at -20°C in high yield, whereas hardly any polymerization of SiVE occurred in the presence of methyl acetate.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 597-609 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Low molecular weight, M̄n 1800-2400, and soluble copolymers of acetylene and butadiene were prepared by nickel naphthenate-diethylaluminum chloride catalyst. These copolymers possess high cure tendency to give insoluble and highly crosslinked films. The curing ability can be controlled by the amount of acetylene content in the copolymer and is in the following order: acetylene-butadiene copolymer 〉 tung oil 〉 cis-1,4-polybutadiene ≫ linseed oil, 1,2-polybutadiene, butadiene-isobutylene copolymer. Chemical modifications of the copolymer such as maleic reaction, metallation by lithium or sodium, graft polymerization by methyl methacrylate, 4-vinylpyridine or vinyl acetate, and epoxidation were also examined. The divinyl methylene in the copolymer gives a high cure tendency and high chemical reactivity.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 879-887 
    ISSN: 0887-624X
    Schlagwort(e): living cationic polymerization ; isobutyl vinyl ether ; added Lewis base ; EtAlCl2 ; Et1.5AlCl1.5 ; polymerization mechanism ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In the living cationic polymerization of isobutyl vinyl ether (IBVE) by the CH3CH (OiBu) OCOCH3 (1)/EtAlCl2 initiating system in the presence of the added base in hexane at +40°C, the stability of the initiating system 1/EtAlCl2, which form initiating species CH3CH⊕ (OiBu) derived from 1, was investigated. In the presence of the Lewis base such as ethyl acetate or 1,4-dioxane, the active species was stable for 300 min even at +40°C in the absence of IBVE, and the living polymers were quantitatively obtained by adding IBVE. However, the active species was partly consumed by side reactions during the standing time for 60 min in the presence of a less basic additive such as ethyl benzoate, and about 50% of the active species was deactivated in the presence of methyl chloroacetate. Consequently, in the case of a less basic additive such as methyl chloroacetate (which was effective for the fast living polymerization), it can be seen that the careful selection of polymerization conditions was required. The living polymerization rate was dependent on the second order of EtAlCl2 concentration. EtAlCl2 induced the cleavage of 1 into CH3CH⊕ (OiBu) and EtAl⊖Cl2(OCOCH3), and the reactivity of CH3CH⊕ (OiBu) and propagating carbocation may be controlled by EtAl⊖Cl2(OCOCH3) with the aid of other EtAlCl2. Et1.5AlCl1.5 exists as a bimetallic complex of EtAlCl2 and Et2AlCl, and it is expected that the polymers having a bimodal molecular weight distribution will be obtained due to two kinds of counteranions coming from EtAlCl2 and Et2AlCl. However, in the cationic polymerization of IBVE by 1/Et1.5AlCl1.5 in the presence of ethyl acetate, the living polymer exhibiting a unimodal and very narrow molecular weight distribution was obtained. Thereby, it was suggested that the counteranions, EtAl⊖Cl2(OCOCH3) and Et2Al⊖Cl(OCOCH3), exchange rapidly with each other. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1195-1198 
    ISSN: 0887-624X
    Schlagwort(e): cis polymerization of butadiene ; copolymerization of butadiene and styrene ; gadolinium tricarboxylate ; effect of pKa of ligand ; polymerization mechanism ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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