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  • 1
    Electronic Resource
    Electronic Resource
    Use of deuterium to investigate extent of branching in polystyreneThis paper was presented at the 123rd National Meeting of the American Chemical Society in Los Angeles, California, March 15, 1953. (1954)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 14 (1954), S. 513-520 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The extent of branching in polystyrene is attributed to a polymer transfer step occurring during polymerization. In this process a radical abstracts a hydrogen atom from along a chain which then adds monomer at the site of the abstraction. The rate of this process should be decreased if the hydrogen is replaced by deuterium, and consequently deuterated monomers should polymerize to form polymers less branched than those from the nondeuterated monomer. Polymers of α- and β-deuterostyrene were synthesized and thier intrinsic viscosity and molecular weight by light scattering determined. In the case of the α-deuterostyrene, the polymer was also fractionated and measurements were made on the fractions. The data for the deuterated styrenes fit quite closely the same relationships as a normal styrene sample prepared simultaneously and under the same conditions, i.e., 70°C. and without catalyst. The results indicate, therefore, that branching is quite small in polystyrene prepared under such typical conditions. A check of the isotope effect on the transfer process was made utilizing S-deuterobutyl mercaptan. A value of 4.0 was obtained at 60°C. for the relative rate of transfer with butyl mercaptan to that for the deuterated mercaptan.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1954.120147801
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  • 2
    Electronic Resource
    Electronic Resource
    Pyrolysis of α- and β-deuterostyrene polymers (1955)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 15 (1955), S. 157-166 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recently the depolymerization of addition polymers has been treated in terms of four elementary reactions: initiation, propagation, transfer, and termination; analogous to those reactions which operate in the polymerization process. It is the transfer process which, according to its relative importance, gives rise to differences in polymers in the monomer yield, in the rate vs. conversion behavior, and in the molecular weight vs. conversion behavior. The transfer process is assumed to operate through the abstraction of a hydrogen from the polymer chain by a radical. By substituting a deuterium for the hydrogen at selected points in the polymer chain, the amount of the transfer process should be decreased due to an isotope effect. Two deuterated polymers were made from α- and β-deuterated styrenes and their depolymerization behavior studied. In the case of the α-deuterostyrene polymer the results are compatible with a ½ decrease in the rate of the transfer process and also an increase in the rate of the propagation. The results with the β-polymer imply an increase in both the transfer and propagation rates. The data obtained indicate that in polystyrene the intermolecular transfer process is mainly responsible for the fall in molecular weight of the polymer residue during depolymerization.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1955.120157913
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular weight standards from sulfonation of polystyrene (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 1039-1046 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polystyrene was sulfonated with sulfur trioxide-triethyl phosphate complexes in dichloroethane, the object being to prepare polystyrene sulfonates substantially free of sulfone links between polymer chains. Variations in the sulfone content with reaction conditions were conveniently followed by exclusion chromatography, the sulfone peak appearing at about twice the molecular weight of the main peak. The desired products were obtained from polystyrenes with molecular weights between 1.1 × 105 and 8.7 × 105 by using (at -20 to +25°C) a 5:1 excess of a 1.5:1 complex, the last at a concentration of 0.5M. Completely soluble polystyrene sulfonate was also obtained from polystyrene of molecular weight 2.05 × 106. Requirements for the successful use of the 1.5:1 complex include careful purification of the dichloroethane and, if 2 g or more polystyrene is to be sulfonated, formation of the complex at -20°C. A method is given for measuring the sulfonating capability of the reagent before adding the polymer.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170409
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  • 4
    Electronic Resource
    Electronic Resource
    Melanin-concentrating hormone: A structural and conformational study based on synthesis, biological activity, high-field nmr, and molecular modeling techniques (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 609-622 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of Melanin-concentrating hormone (MCH) fragments have been synthesized and their biological activities compared with the parent peptide. The substructural units, 5-14 linear and 5-14 cyclic, have been used as models for MCH -  in 1H-nmr conformational studies. Conformational features predicted by molecular dynamics analyses find support in the nmr experiments.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290314
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  • 5
    Electronic Resource
    Electronic Resource
    Accessible conformations of melanin-concentrating hormone: A molecular dynamics approach (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 623-637 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular dynamics simulations have been used to search for the accessible conformations of the melanin-concentrationg hormone (MCH). The studies have been performed on native MCH and two of its peptide fragments, a cyclic MCH(5-14) fragment and a linear MCH(5-14) fragment. An analysis of the molecular dynamics trajectories of the three peptides indicates that two regions of the peptide have characteristic conformational properties that may be important for the biological activity. One is a region around Gly8, which is conformationally mobile, and the other is around Pro13, which shows unusual rigidity. The molecular dynamics simulation results are discussed in terms of backbone structural features like β turns, side-chain interactions, and orientations of the disulfide bridge. The results of this analysis are used to suggest new analogues that will modify the conformational features of the peptide and further define the conformational requirements for activity. Finally, the results are related to nmr studies of the peptide and reveal agreements between the experimental nuclear Overhauser effect constraints and some of the accessible conformations obtained from the simulation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290315
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  • 6
    Electronic Resource
    Electronic Resource
    Radiation-induced polymerization and other reactions of n-perfluoropentadiene-1,4 at high temperature and pressureBased on research supported by the U.S. Army Research Office, Durham, North Carolina. Presented in part at the Division of Polymer Chemistry, 145th National American Chemical Society Meeting, New York, New York, September 1963, Preprints p. 426. (1965)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 3 (1965), S. 1641-1660 
    Details
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The radiation-induced polymerization of n-perfluoropentadiene-1,4 was studied at temperatures of 100-170°C. and pressures of 8,000-15,000 atm. Kinetic evidence indicates that polymerization occurs by a free radical reaction; the activation energy is between 14 and 17 kcal./mole and the activation entropy is -8 ± 5 e.u./mole. Transfer with monomer limits the number-average degree of polymerization to values of 40 or less except in special circumstances. Dimerization and double bond migration occur to some extent; n-perfluoropentadiene-1,3 is formed in the latter process. It and the 1,4-diene copolymerize; the latter undergoes cyclic addition so that the polymers are soluble and have little perfluorovinyl unsaturation. The polymers are brittle if the fraction of 1,3-diene in the polymer is less than 0.1. They are rubbery and of considerably higher molecular weight if the fraction of 1,3-diene is greater than 0.4. The thermal stability of the polymers decreases as the content of 1,3-diene increases.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1965.100030431
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  • 7
    Electronic Resource
    Electronic Resource
    Electron spin resonance spectra of aged, γ-irradiated polystyrenesPaper presented before the 140th National Meeting of the American Chemical Society, Chicago, September 4, 1961. (1963)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 1 (1963), S. 1521-1529 
    Details
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The electron spin resonance spectrum of polystyrene that has been γ-irradiated at -196°C. changes gradually with time from a broad three-peaked structure with outer derivative peaks at ±46 gauss to a much narrower structure with poorly separated outer derivative peaks at ±21-24 gauss. The deuterated polystyrenes behave likewise in general. The aged radicals of α,β,β-trideuterostyrene and β,β-dideuterostyrene exhibit only a single peak with derivative maxima at ±7 or 8 gauss from center. The aged spectra are all consistent with the hypothesis of major hyperfine interaction with β hydrogens. During the aging about 80% of the original radicals are lost, but the remainder are very long-lived. Poorly evacuated samples or those with added benzene decay much more rapidly.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1963.100010506
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  • 8
    Electronic Resource
    Electronic Resource
    Radiation-induced polymerization of hexafluoropropylene at high temperature and pressure (1966)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 4 (1966), S. 2229-2240 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radiation-induced polymerization of hexafluoropropylene was studied in the pressure and temperature ranges of 4,500-15,000 atm. and 100-230°C., respectively. Retardation was a serious problem; data thought to apply to the unretarded polymerization are summarized below. At 1,500 rad/hr. the polymerization rate was 15%/hr. at 230°C. and 15,000 atm. The activation enthalpy and volume are 9.5 kcal./mole and -10 cc./mole, respectively. The rate varies as the square root of the radiation intensity. The largest intrinsic viscosity of the polymer is 2.0 dl./g.; values increase with temperature and pressure. At 130°C. and 10,000 atm. the intrinsic viscosity was the same at two radiation intensities.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1966.150040917
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