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  • Polymer and Materials Science  (35)
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  • 1
    Electronic Resource
    Electronic Resource
    Helix-Coil transition in polypeptides: A microscopical approach (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 357-367 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analogous with the Potts model that describes the helix-coil transition in the isolated polypeptide chain (a Hamiltonian model allowing for the energy U of hydrogen bond formation) the number Q of conformational states of a repeating unit of the chain and the topology of Δ = 3 hydrogen bond formation (the hydrogen bond fixing three pairs of ϕψ chain rotations) has been constructed and the corresponding transfer-matrix has been obtained. In the thermodynamical limit, the partition function is expressed through the principal root of the cubic equation. The degree of helicity, the transition point and range, the correlation length, the number of junctions between the helical and coiling sections as well as the mean length of helical and coiling sections are calculated. Empirically introduced parameters of the Zimm-Bragg theory, constants of hydrogen bond formation s, and the cooperativity parameter σ as functions of microscopic parameters U, Q, and Δ are obtained by direct calculations. The behavior of this model was investigated at other topologies of the hydrogen-bond closing Δ = 2 and Δ = 4, and it was suggested that the actual polypeptide chain (Δ = 3) provides the optimum correlation of helical structure of the order of globule dimensions. An expression was obtained for the maximum correlation length of the order ξ ∼ Q(Δ-1)/2. For a System with solvent competing for the formation of hydrogen bonds with peptide groups a Hamiltonian model was constructed that took account of the energy E of the formation of hydrogen bond with the solvent and the number q of orientations of a solvent molecule about the peptide groups. It is shown that by the redefinition of the temperature parameter, the model with solvent reduces to the model of an isolated chain. Aside from the definition relationship that exists between the parameters of the theory U 〈 2E 〈 Uq and the ordinary helix-coil transitions (“melting”), the model also describes the transition from the coiling state to the helical one (“arrangement”) under heating. The change in temperature and transition range with solvent parameters was discussed and it was shown, that despite the difference in ΔT for the given polypeptide chain (Q = constant) with different solvent parameters, at “melting” and “arrangement,” the transition occurred at the same correlation length (the same cooperativity).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300313
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  • 2
    Electronic Resource
    Electronic Resource
    The helix-coil transition in polypeptides: A microscopic approach. II (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 75-84 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the framework of an earlier constructed model [N. S. Ananikyan et al. (1990) Biopolymers, Vol. 30. pp. 357-367], some analytical estimates for the correlation length and degree of helicity near the transition point were obtained in the case of an arbitrary topology of hydrogen bond closing (Δ). It was shown that the Zimm-Bragg cooperativity parameter σ is determined by the set of (Δ-1) amino acid residues and so is nonlocal. An analytic expression for cooperatively parameters in a heteropolypeptide chain was obtained and numerical calculations showed that in case of heteropolypeptide with random primary structure the nonlocality of cooperativity parameter influenced the temperature dependence of helicity degree. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350108
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  • 3
    Electronic Resource
    Electronic Resource
    Graft polymerization of methyl methacrylate onto nylon 6 using pentavalent vanadium as initiator (1981)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 96 (1981), S. 59-68 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde die durch 5wertiges Vanadium induzierte Pfropfcopolymerisation von Methylmethacrylat auf Nylon 6 untersucht. Die Pfropfausbeute sowie der Gesamtumsatz wurden in Abhängigkeit von der Vanadiumkonzentration, des Lösungsmittelgemisches sowie der Reaktionstemperatur bestimmt.
    Notes: Pentavalent vanadium ion (Vv)-induced graft polymerization of methyl methacrylate onto nylon 6 was investigated under a variety of conditions. Increasing the Vv-concentration up to 2 mmol/l was accompanied by an enhancement in grafting; the latter was not affected by further increase in Vv-concentration. Unlike grafting, the homopolymer and total conversion tended to increase by increasing Vv concentration. The graft yield enhanced significantly when the MMA-concentration was increased up to 3% further increase in MMA-concentration had no effect on grafting. Raising the polymerization temperature from 50° up to 70°C caused a significant increase in the rates of grafting, homopolymerization and total conversion. Using a solvent-water mixture as medium for polymerization affected considerably the magnitude of grafting. While using methyl alcohol, ethyl alcohol and acetone at any ratio in the solvent-water mixture resulted in decreased grafting, using an isopropyl alcohol-water mixture up to a ratio of 25 : 75 gave rise to increased grafting.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1981.050960105
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular parameters and conformational conversions of poly(N-vinyl-2-pyrrolidone) on complex formation with cobalt ions (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 6 (1984), S. 277-285 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The hydrodynamic properties of dilute solutions of poly(N-viny1-2-pyrrolidone) (PVP) and its Co(II) complexes were studied by high-speed sedimentation and viscosimetry methods. Unperturbed dimensions of PVP in two solvents (ethyl alcohol and water) and those of PVP complexes with the cobalt ions in water were determined. Unperturbed dimensions of PVP coils were shown to be dependent on the solvent nature, and those of polymer-metal complexes on metal concentration.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.020061984121
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  • 5
    Electronic Resource
    Electronic Resource
    Hetero-chain polymers based on natural amino acids. Synthesis of polyamides from Nα, Nε-bis(trimethylsilyl)lysine alkyl esters (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 939-954 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: High-molecular-weight polyamides based on the natural amino acid lysine were synthesized by condensation of Nα, Nε-bis(trimethylsilyl)lysine alkyl esters (1a-c) with derivatives of aromatic dicarboxylic acids (2a-c). The best results were obtained with diacyl dichlorides. However, in the case of aliphatic dicarboxylic acid derivatives, preference should be given to their active diesters. The properties of the resulting polyamides were shown to be determined, to a considerable degree, by the nature of the reaction medium. Polyamides with free carboxyl groups, capable of further polymeranalogous conversions, were obtained by means of saponification of the side chain alkyl ester groups. The substituted phenols, resulting from the polycondensation of 1a-c with active diesters, could be used for the synthesis of polyamides with active ester groups in the side chains.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021860506
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  • 6
    Electronic Resource
    Electronic Resource
    Ring-opening metathesis polymerization of norbornenes with organosilicon substituents. Gas permeability of polymers obtained (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 1-9 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymers of norbornenes with SiMe3 and Si(Me2)CH2SiMe3 groups were synthesized and mass transfer properties of the polymers were studied. Ring-opening polymerizations of these monomers were realized in the presence of homogeneous WCl6-based and heterogeneous Re2O7-based metathesis catalysts. Introduction of silicon-containing groups in the polynorbornene main chain results in a drastic increase of the permeability (P) and diffusion (D) coefficients for different biatomic and multiatomic gases. Comparison of polymers having SiMe3 and Si(Me2)CH2SiMe3 substituents shows lower permeability and diffusion coefficients in the latter case. The combination of transport properties (Pi values) and separation factors aij = Pi/Pj of the two new silicon-containing polynorbornenes permits one to consider them as representatives of the most permeable and sufficiently permselective group of polymers. Transport properties of the polymers studied were analysed on the basis of the free volume approach.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920101
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  • 7
    Electronic Resource
    Electronic Resource
    Reactivity of individual stereoisomers based on 4-(3-buten-1-ynyl)-1,2,5-trimethyl-4-piperidinol in radical polymerizationRevised Manuscript of August 29, 1991. (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 1557-1566 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The radical polymerization of individual stereoisomers of 4-(3-buten-1-ynyl)-1,2,5-trimethyl-4-piperidinol (1) was investigated. The reaction order with respect to the monomer and the initiator, and also the kinetic and energetic parameters of the polymerization reaction were determined. The values of constants of polymerization of the stereoisomers were found with the help of the “rotating sector” method. It was established that the spatial orientation of the reactive centres with respect to the six-membered heterocycle influences the reactivity of the monomers and leads to a change of the polymerization rate of the stereoisomers by a factor of about 1,5 to 3. To ascertain the influence of the spatial structure on the reactivity of the stereoisomers, quantum chemical calculations for model structures were performed. By means of IR and Raman spectroscopy it was established that the polymerization of 1 occurs via the double bond of the 3-buten-1-ynyl groups.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930631
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  • 8
    Electronic Resource
    Electronic Resource
    Alternating copolymerization of maleic anhydride with allyl chloroacetate (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 711-717 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some regularities of radical alternating copolymerization of maleic anhydride with allyl chloroacetate are studied. The formation of donor-acceptor complexes between comonomers with complexing constant Kc = 0.052 L/mol is found using 1H NMR spectroscopy. The kinetic parameters for this copolymerization reaction are found and the quantitative contribution of monomer complexes to chain-growth radical reactions is calculated. It is shown that either a “free-monomer” mechanism (dilute solutions) or a “mixed” mechanism (concentrated solutions) prevails for chain growth during radical copolymerization depending on total monomer concentration. It is found that inhibition of degradative chain transfer in the course of the reaction studied takes place owing to the presence of α-chlorine atom in the allyl chloracetate molecule and formation of charge transfer complex.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080250222
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  • 9
    Electronic Resource
    Electronic Resource
    Über Oxydationsfiguren auf Metalloberflächen (1957)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 8 (1957), S. 733-735 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: On the figures of oxidation on metal surfacesThe contribution presents some supermicroscopic investigations which demonstrate that oxide layers on metal surfaces are genniue figures of oxidation. By their means you can determine the lattice type of metals and alloys.
    Notes: In dem vorliegenden Beitrag wird sinnfällig gezeigt, daß sich die auf Metalloberflächen befindlichen Oxydhäute bei der elektronenmikroskopischen Untersuchung als echte Oxydations-figuren erweisen, die Auskunft über den Gittertyp der Metalle und Legierungen geben.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19570081202
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  • 10
    Electronic Resource
    Electronic Resource
    Studies on the Pitting Corrosion of the Delta-52 Steel in aqueous solutions. 2. Variation of the pitting potential in relation to the concentration of the aggressive anion (1976)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 27 (1976), S. 630-636 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Untersuchungen zur Lochkorrosion des Stahls Delta-52 in wässerigen Lösungen. -2. Änderung des Lochkorrosionspotentials in Abhängigkeit von der Konzentration des angreifenden AnionsDie potentiodynamischen anodischen Polarisationskurven wurden für eine Elektrode aus dem Stahl Delta-52 (0, 40, C, 0, 78Mn, 0, 045S, 0, 06p, 0, 23Si) aufgenommen; als Prüflösung diente verdünntes KOH mit und ohne Zusatz von Kaliumchlorid, -bromid und -jodid. Der auf dem Stahl vorhandene Oxidfilm beeinflußt die aktive Auflösung nicht, erst bei Potentialen über+2 V (ges. Calomal) tritt Passivität auf. Das Polarisationsverhalten des Stahls wird durch Zusatz der Halidionen nicht beeinflußt; oberhalb einer bestimmten Konzentration der Halide nimmt jedoch der Auflösungsstrom plötzlich steil zu, was auf den Beginn von Lochkorrosion hinweist; zwischen dem Lochkorrosionspotential und der Konzentration der Anionen besteht eine eindeutige Beziehung.
    Notes: Potentiodynamic anodic polarization curves have been traced for an electrode of the steel Delta-52 (0.40, 0.78Mn, 0.045 S, 0.06P, 0.23 Si): the aggresive media used were potassium hydroxide without and with additions of potassium chloride, bromide and iodide. The oxide film present on the steel surface does not inhibit active dissolution; only at potentials exceeding+2 (S. C. E.) passivity sets in. The polarization behaviour of the steel is not influenced by the addition of the halide salts; above a certain salt concentration, however, there is a sharp increase in dissolution current. This phenomenon is an indication of the start of pitting. Between the pitting potential and the anion concentration there exists a well defined relation.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19760270905
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