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  • Wiley-Blackwell  (142)
  • American Physical Society  (68)
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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 805-815 
    ISSN: 0887-624X
    Keywords: polystyrene ; sorption ; desorption ; evaporation ; polymer-inclusion complexes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The results obtained in time studies that monitored evaporation from liquid-saturated poly(styrene-co-divinylbenzene) to virtual dryness at temperatures ranging from 20 to 80°C confirm those reported earlier for multireplicated time studies at 23 ± 1°C; i.e., when the residual composition (αt, in sorbed molecules per phenyl group) attains the glassy state composition, the value of αt thereafter is given by a linear combination of no more than six exponential decay functions. The logarithms of the rate constants (ki) for decay of these populations at a given temperature decreased linearly with i, the population identification number in the order of decreasing decay rate. The Arrhenius activation energy (ΔEi) for increase in ki with temperature was characteristic of the sorbed species, but it was independent of i. The logarithms of the frequency factors (Ai) decreased linearly with i, the slope of which was numerically equal to that observed for the corresponding ki relationships, signifying that the stepwise decrease of the latter at a given temperature is attributable primarily to a corresponding incremental decrease in entropy. It is suggested that this reflects discrete changes in the molecular structure of polymeric inclusion complexes formed during the transition from the rubbery to the glassy state, as discussed in the text. © 1993 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 65 (1909), S. 117-135 
    ISSN: 0863-1778
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 224 (1935), S. 23-24 
    ISSN: 0863-1786
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Weder durch Anbau von Wasserdampf an Orthoborsäure noch beim Abbau gesättigter Borsäurelösung konnte bei O° ein höheres Borsäurehydrat in festem Zustand gefaßt werden.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 649-667 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In these time studies of evaporation from liquid-saturated microporous composite film samples, comprised of poly(styrene-co-divinylbenezene) particles enmeshed in poly(tetrafluoroethylene) microfibers, the samples were preswelled to saturation in a good solvent, such as toluene, which was then replaced via solvent exchange in excess test liquid before the start of the time study that monitored the residual weight (Wt) of sorbed liquid to virtual dryness. The patterns of change with time (i.e., Wt. vs. t and Log Wt vs. t) obtained thereby were compared with the corresponding time studies already reported for evaporation from equivalent polystyrene-liquid (PS-L) systems that did not have a history of preswelling in a better solvent. These comparisons show that the history of the samples in its liquid-saturated gel state can affect markedly the kinetics of desorption from the PS-L system in its glassy state, and also during the interval of transition from the rubbery state to the glassy state, as discussed in the text. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 5
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This kinetic restudy of the physical changes that occur during evaporation-induced transition from the rubbery to a glassy state of polystyrene-liquid systems shows that such transitions occur via two mechanistic pathways. The first is random nucleation of microdomains of self-associated polymer segments owing to a time-dependent logarithmic decrease in the number of adsorbed volatile molecules per phenyl group of residual mobile polymer segments. The second is a therodynamically driven self-association of adjacent monomer units with concomitant explusion of the adsorbed molecules, which appears to propagate via a “dominolike” chain reaction. Conceptually this is a three-dimensional “zippering-up” of suitably close polymer segments to produce the corresponding macrostructural network of self-associated polymer. The kinetics of the latter is zero-order, and this dominates the overall kinetics of evaporation during the latter portion of the transition interval, presumably owing to changes in entropy of the system as it progresses from the mobility characteristic of the rubbery state to the rigidity characteristic of a glassy state. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 224 (1935), S. 1-22 
    ISSN: 0863-1786
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1. Der Abbau von Na2B4O7·10H2O schlägt, wie durch tensimetrische Messungen und durch Entwässerungsversuche über Trockenmitteln erkannt, je nach Vorbehandlung der untersuchten Präparate zwei grundsätzlich verschiedene Wege ein: Ein zuvor auf etwa 50° angetempertes Zehnhydrat geht in scharf ausgeprägter Stufe (10 mm isobar bei 20°) reversibel in kristallines Fünfhydrat über  -  „stabiler Abbau“  - , und dessen weiteres Verhalten entspricht ganz dem des oberhalb 60° aus Lösung kristallisierenden Pentahydrates. Frisch umkristallisiertes, „ungeschmortes“ Zehnhydrat hingegen wird bei gleicher Temperatur unter Entwicklung eines sehr viel kleineren Dampfdruckes, selbst nach langen Reaktionszeiten, zu einer viel wasserärmeren Stufe abgebaut. Der Bodenkörper zeigt bei einem Restgehalt von 5Mol H2O noch deutlich, bei 3 Mol und darunter abklingend die Interferenzen des Zehnhydrates neben zunehmend amorpher Beschaffenheit, die mit 2 Mol Restwasser praktisch voll erreicht ist. Dieser „instabile Abbauvorgang“ ist nicht reversibel; vorsichtige Wiederanwässerung der Rückstände aus dem Dampfraum oder auch leichtes Antempern der zwischen 10 und 3H2O liegenden Bodenkörper, etwa auf 50°, fuhrt diese „instabilen“ Abbausysteme in die „stabilen“ Verhältnisse über, d. h. veranlaßt  -  rontgenographisch festgestellt  -  die Bildung des Fünfhydrates.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 277-280 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of the number of oxyethylene repeating units in the oligomeric derivatives of ethylene bis(4-chlorocarbonylbenzoate) (1, n = 3, 6,4, 13, 22,3, 45 and 68) on the reactivity of the chlorocarbonyl end groups in the acceptor-catalytic esterification was determined by means of thermodynamic and kinetic investigations in diluted solutions. The violation of the principle of equal reactivity was found to be caused by the far-order effect, when with increasing chain length the effective local concentration of oxyethylene repeating units increases in the environment of the end group whose reactivity is determined by the ratio between the “solvating ability” of the repeating units and the solvent. The far-order effect influences not only the kinetics, but also the reaction mechanism.
    Additional Material: 6 Ill.
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  • 9
    ISSN: 0947-3440
    Keywords: Heck reaction, intramolecular ; α-Amino acids ; Isoquinolines ; Palladium ; Heterocycles ; Synthesis, enantioselective ; High pressure ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkylation and acylation of the alkenes 9b, c and 10a, b, which are easily prepared from the corresponding α-amino alcohols, with 2-halobenzyl and 2-halobenzoyl halides respectively, gives 11-15. These compounds cyclize with excellent diastereo- and regioselectivity to the enantiomerically pure N-heterocycles 18-20 in an intramolecular Heck reaction using 5 mol-% of Pd(OAc)2 in the presence of PPh3, TPAB and KOAc. Under the same conditions substrate 17 leads to the enantiomerically pure benzazepine 24. The reaction of the bromoarene derivatives 14-15 must be performed under high pressure to give good results.
    Additional Material: 1 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 887-891 
    ISSN: 0947-3440
    Keywords: Heck reaction, intramolecular ; Isochromane ; Palladium ; Heterocycles ; High-pressure chemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The iodoarenes 9 and 10, bearing (E)- and (Z)-alkene moieties, respectively, easily prepared by alkylation of the corresponding alcohols 7a-c and 8a-c with 2 iodobenzyl iodide, undergo intramolecular Heck reactions to give the isochromanes 12-15a-c in good yields. The selectivity of the reaction depends on the size of the substituent R in 9 and 10; increasing bulkiness of R leads to a decrease in diastereoselectivity and an increase in regioselectivity. High-pressure experiments confirm the proposed mechanism and show that bromoarenes such as 11, which tend to be unreactive at ambient pressure, give good results when the cyclisation is performed under high pressure.
    Additional Material: 1 Tab.
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