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  • 1
    Electronic Resource
    Electronic Resource
    Tetragonal-to-Cubic Structural Phase Transition in Pollucite by Low-Temperature X-ray Powder Diffraction (1997)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The tetragonal-to-cubic structural phase transition in pollucite (CsAlSi2O6) was investigated using low-temperature X-ray powder diffraction in the temperature range of 93 to 298 K, and the lattice constants were refined with Rietveld analysis. It was found that CsAlSi2O6 had a tetragonal phase with a space group of I41/acd in the temperature range of 93 to 248 K, a = 1.36337(4) nm, c = 1.36988(6) nm at 248 K, and underwent a phase transition from tetragonal to cubic with a space group of Ia-3 in the temperature range of 248 to 273 K, a = 1.36645(3) nm at 273 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1997.tb03175.x
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  • 2
    Electronic Resource
    Electronic Resource
    Solid-state polymerization of long-chain vinyl compounds. II. Effect of molecular arrangement on polymerizability of octadecyl acrylate (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 2947-2959 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To clarify the effect of a molecular arrangement of long-chain monomers on polymerizability, γ-ray-initiated postpolymerization of polymorphic crystals of octadecyl acrylate and the melt has been investigated. According to thermal, x-ray, and infrared (IR) analyses octadecyl acrylate exhibit three crystalline modifications similar to, but different in transition behavior from, those of octadecyl methacrylate. The α-form is stable in the range of 19-32°C (mp) and at lower temperatures the β-form is stable, whereas the sub-α-form appears transiently in α → β transition. The monomer molecules in triclinic packing (α-form) show little tendency to polymerize, whereas those in hexagonal packing (β-form) have high polymerizability that increases with temperature. The polymerizability in the molten state at fairly high temperatures is rather low, however. Thus the polymerization rate, saturated conversion, and polymer molecular weight exhibit maxima just above the melting point of α-form. It is concluded that the hexagonal packing of monomer molecules with particular orientation in the layered structure and rotational freedom around the molecular axis, together with some conformational freedom of functional group, is favorable to the polymerization reaction. In addition, the mechanism of polymerization in the layered structure is discussed, assuming a cone-type distribution for the polymerization probability.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170930
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  • 3
    Electronic Resource
    Electronic Resource
    Solid-state polymerization of long-chain vinyl compounds. IV. Effects of chain length on the polymorphic behavior and postpolymerization of n-alkyl methacrylates (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 2437-2449 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymorphic behavior and γ-ray-initiated postpolymerization of the even-numbered long-chain Methacrylates (C18-C12) have been investigated. Phase transition behaviors of octadecyl, hexadecyl, tetradecyl, and dodecyl methacrylates are respectively, which become simpler with shortening of the chain length. The methacrylate monomers with sufficiently long hydrocarbon chains, such as octadecyl and hexadecyl, can be polymerized rapidly in the α-form crystal (hexagonal packing) by a fully two-dimensional mechanism, whereas in the β-form crystal (triclinic packing), polymerization can hardly occur. In the case of dodecyl methacrylate, however, an accelerated polymerization in the β form occurs after an induction period of several hours and the resultant polymer is gel-like. This can be interpreted by the propagation reaction across the polymer chain already formed. It has been found that the solid-state post-polymerization of n-alkyl methacrylates is affected by the chain length through the packing mode of the monomer molecules and also by the aggregation state of side chains in the resultant comblike polymer.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180803
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  • 4
    Electronic Resource
    Electronic Resource
    Solid-state polymerization of long-chain vinyl compounds. VI. In-source polymerization of octadecyl acrylate by γ-ray irradiation (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 443-449 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The in-source polymerization of octadecyl acrylate in the lamellar crystal (hexagonal packing) by γ-ray irradiation has been investigated, as compared with the two-step and one-step postpolymerizations. The viscosity-average molecular weight is very high even in the initial stage and is practically saturated after 3-5 hr, although the conversion increases successively with time. The molecular weight distribution of poly(octadecyl acrylate) obtained by in-source polymerization is very wide (Mw/Mn = 13.1, at 20°C). The results of in-source polymerization of the long-chain vinyl compounds can be interpreted using the cone model for polymerization probability, similar to those of one-step and two-step postpolymerizations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190219
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  • 5
    Electronic Resource
    Electronic Resource
    Solid-state polymerization of long-chain vinyl compounds. I. Effect of molecular arrangement on polymerizability of octadecyl methacrylate (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 2387-2400 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: γ-Ray-initiated postpolymerization of octadecyl methacrylate in polymorphic crystals and melt has been investigated to clarify the effect of molecular arrangement of the monomer on polymerizability. From thermal, x-ray, and infrared (IR) analyses this long-chain monomer exhibited three crystalline modifications that we refer to as α-, sub-α, and β-forms. The β-form (mp 28.7-29.7°C), which is obtainable from solution, is a stable state with triclinic chain packing. The α-form (mp 19.5-20.0°C), which is obtained first from the melt but transforms into β-form on storing, is a metastable state with hexagonal chain packing. The sub-α-form appears transiently in α→β transition. The polymerizability of octadecyl methacrylate in the β-form is extremely low, whereas the α-form can polymerize easily and the initial polymerization rate, saturated conversion, and polymer molecular weights increase with temperature. Polymerizability in the molten state at fairly high temperature is rather low, however. Thus maximum polymerizability is obtained just above the melting point of α-form. It has been found that particular orientation and suitable packing mode with some freedom of rotational motion of the monomer molecules in layered structure accelerate the polymerization reaction.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170811
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  • 6
    Electronic Resource
    Electronic Resource
    Solid-state polymerization of long-chain vinyl compounds. III. Mechanism of γ-ray-initiated postpolymerization in layered structures of octadecyl methacrylate and acrylate (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 1693-1709 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism and kinetics of the γ-ray-initiated postpolymerization of octadecyl methacrylate and acrylate in lamellar crystals were investigated by a simple model. This model assumes that the initiation points are distributed as in a checkerboard and that polymerization probability of the monomer molecules decreases conically around each initiation point. The two-dimensional polymerization can be characterized in this cone model by two parameters, a and r; a represents the polymerizability of the monomer for a given condition, and r depends on the number of initiation points per unit area. G values for the initiation reaction of octadecyl methacrylate and acrylate were estimated as 0.8 and 1.6, respectively. The two-dimensional postpolymerization of long-chain compounds proceeds in two stages. The rate of polymerization is very high and zero order with respect to monomer concentration in the first stage. It is lower and obeys first-order kinetics in the second stage. The rate constants of the zero-and first-order polymerizations were kp0 = 1.73 molecule sec-1 and kp1 = 0.93 sec-1, respectively, for octadecyl acrylate at 20°C.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180605
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  • 7
    Electronic Resource
    Electronic Resource
    Solid-state polymerization of long-chain vinyl compounds. V. Two-step postpolymerization of octadecyl acrylate by temperature increase and by stepwise γ-ray irradiation (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 257-270 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of two-dimensional polymerization of octadecyl acrylate in lamellar crystal was investigated in two-step postpolymerizations by temperature increase and stepwiseγ-ray irradiation in lieu of the usual one-step reaction. Two-step postpolymerizations by these procedures are interpreted satisfactorily by the cone model, which assumes that the polymerization probability of the monomer molecules in a single layer is distributed conically around the initiation point. It was found that the propagating radicals were living, even in the saturated stage, and the effect of the polymer chains already formed on the propagating and terminating reactions was evident. Furthermore, molecular weight distributions of the resultant poly(octadecyl acrylate) measured by gel permeation chromatography (GPC) were broad. The values of Mw/Mn for the two-step post polymerizations were 4.71-7.03, whereas those for one-step reactions were 3.26-5.54.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190204
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  • 8
    Electronic Resource
    Electronic Resource
    Solid-state polymerization of long-chain vinyl compounds. IV. Effects of chain length on the polymorphic behavior and postpolymerization of n-alkyl methacrylates (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 849-849 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190325
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  • 9
    Electronic Resource
    Electronic Resource
    Boundary effect on the thermal degradation of copolymers (1967)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 5 (1967), S. 21-34 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of thermal degradation of vinyl-type copolymers at high temperatures was investigated theoretically and experimentally. A parameter β was proposed to account for the boundary effect. Values of β for acrylonitrile-styrene and methyl methacrylate-styrene copolymers were determined experimentally. It was ascertained that the value of β was independent of the distribution of monomer sequence lengths in a copolymer, but dependent on the pyrolysis temperature and on the nature of the copolymer. The boundary effect is attributed to differences in the dissociation energies of C—C bonds connecting terminal monomer units to adjacent monomer units in copolymer chain radicals.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1967.150050103
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  • 10
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    Study on microstructures of mixed monolayers of poly (octadecylacrylate) and octadecanol in relation to the retardation of water evaporation (1998)
    Elsevier
    Details
    Publication Date: 1998-08-01
    Print ISSN: 0040-6090
    Electronic ISSN: 1879-2731
    Topics: Physics
    Published by Elsevier
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