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  • 1
    Electronic Resource
    Electronic Resource
    Molecular aspects of rubberlike elasticityPaper presented at the meeting of the GDCh Fachgruppe “Makromolekulare Chemie” on “Kautschukelastische Polymersysteme” in Bad Nauheim (Germany), March 30-31, 1992 (1992)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 202 (1992), S. 1-30 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular theories of rubberlike elasticity are surveyed, starting with the earliest attempts carried out in the 1930's and ending with work still very much in progress. The models are variously based on phenomenological arguments, affinely-deforming networks, phantom networks, constrained junctions, constrained chains, slip-links, molecular tubes, van der Waals concepts, or rotational isomeric chains. Most of the theories are analytical, but some involve computer simulations based on Monte Carlo methods. The theories are generally for networks of Gaussian chains, but there have been significant advances for non-Gaussian networks as well, and these are particularly important with regard to a better understanding of ultimate properties. The major outstanding problem on the theory side, however, seems to be a quantitative treatment of chain entanglements.There have also been numerous advances on the experimental side. These include preparation of model networks of known structure, accumulation of elasticity data for deformations other than the much-studied simple elongation, development of new characterization techniques (such as fluorescence polarization, and X-ray and neutron scattering), investigation of the phenomenon of gel collapse, borrowing of ideas from the area of bioelastomers, and preparation of novel reinforcing fillers.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1992.052020101
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  • 2
    Electronic Resource
    Electronic Resource
    Conformational aspects of polypeptides. XXIV. Conformational energies of poly-N-methyl-L-alanine chainsFor previous paper in this series, see Goodman and Falxa. (1967)
    New York : Wiley-Blackwell
    Biopolymers 5 (1967), S. 809-814 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energies of the poly-N-methyl-L-alanine chain have been calculated as a function of the rotational angles of its skeletal bonds, taking into account torsional potentials, van der Waals repulsions, and London attractions. Four pronounced minima in the energy were found; the relative magnitudes of the energies at these minima suggest that the preferred conformation of this chain is either a right-handed, approximately threefold helix, or a slightly distorted, left-handed α-helix. Inclusion of an estimate of the dipolar contribution to the total conformational energy does not significantly affect this conclusion.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1967.360050903
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  • 3
    Electronic Resource
    Electronic Resource
    The dependence of the swelling of elastin on elongation, and its importance in fluorescence probe analysis (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1853-1856 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150919
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  • 4
    Electronic Resource
    Electronic Resource
    Recent studies of rubberlike elasticity (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 2 (1979), S. 87-97 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New synthetic techniques are now available for the preparation of “model” polymer networks of known and carefully controlled molecular structure. The preparation of such networks and their utilization in elucidating molecular aspects of rubberlike elasticity are illustrated using highly elastomeric, unfilled networks of polydimethylsiloxane. In one such preparative technique, hydroxyl-terminated chains are end-linked using either a tetrafunctional or trifunctional silicate, in either the undiluted state or in solution. Because of the selectivity and completeness of the reaction, the molecular weight and molecular weight distribution of the network chains are to good approximation those of the chains prior to their end-linking into the network structure. The experimentally determined stress-strain isotherms and degrees of equilibrium swelling of the resulting networks are then used to evaluate the molecular theories of rubberlike elasticity, particularly with regard to the dependence of the elastic modulus and ultimate properties on the degree of cross linking and the cross-link functionality. Another preparative technique employs random and block copolymers containing reactive vinyl groups in known amount and known distribution along the chains. Selectively cross-linking through these sites then yields model networks ranging from random to highly non-random in chain length distribution. These networks are particularly useful for characterizing the effects of very short chains on the average degree of cross-linking or average network chain length as obtained from stress-strain and swelling equilibrium measurements.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.020021979107
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  • 5
    Electronic Resource
    Electronic Resource
    Configurational characteristics of the polysulfides, 1. Dipole moments of poly(pentamethylene sulfide) (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 2555-2563 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(pentamethylene sulfide)Structure-based name: poly(thiopentamethylene). (P5MS) [—S(CH2)5—]x was prepared by the condensation polymerization of nearly equimolar amounts of pentamethylene dibromide and the sodium salt of 1,5-pentanedithiol. Selective precipitations were used to obtain a fraction of the polymer, and dielectric constant measurements on solutions of it in benzene were used to obtain dipole moments over the range 20-60°C. Rotational isomeric state calculations based on conformational energies obtained from semiempirical potential energy functions gave results in fair agreement with experiment. Since extensive previous studies on a number of polyoxides have demonstrated the difficulty in calculating the energy of the O…CH2 interactions, the energy of the corresponding S…CH2 interactions in P5MS was adjusted to obtain better agreement between theory and experiment.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1982.021831025
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  • 6
    Electronic Resource
    Electronic Resource
    Comparisons among some tetraalkoxysilanes in the hydrolytic precipitation of silica into elastomeric networks (1986)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 2861-2866 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Four tetraalkoxysilanes Si(OR)4 were absorbed into networks of polydimethylsiloxane and then hydrolyzed, using a variety of catalysts, to give reinforcing silica particles. On the basis of the amount of silica precipitated and the extent of reinforcement, the (decreasing) order of effectiveness was found to be tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and tetramethoxysilane.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1986.021871213
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  • 7
    Electronic Resource
    Electronic Resource
    Configurational characteristics of the polysulfides, Part 1, cf.15. Dipole moments and gauche effects in poly (1,3-dithiocane) (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 2565-2572 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several earlier studies of poly(alkylene sulfides) have not yielded evidence for a sulfur gauche effect, in contrast to the large attractive gauche effect found particularly in the lower members of the poly(alkylene oxides). In this study the dipole moments at 25°C and the corresponding temperature coefficient of poly(1,3-dithiocane)Structure based name: poly(thiomethylonethiopentamethylene). [—SCH2S(CH2)5—]x are calculated in the rotational isomeric-state approximation, and the results compared to the values determined by experiment. In the calculations the energy Eσ′ = [Eg± - Et] associated with S. . .CH2 interactions in the SCH2—SCH2 segment is adjusted to attain agreement between theory and experiment. The results indicate that an extra stabilization energy of ca. 0,9 kcal . mol-1 must be added to these gauche states relative to the trans state (beyond that determined by conformational energy calculations based on semiempirical potential energy functions). This provides the first evidence of a large attractive sulfur gauche effect in the polysulfides, about equal in magnitude to that found for the analogous poly(methylene oxide).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1982.021831026
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  • 8
    Electronic Resource
    Electronic Resource
    Configurational chracteristics of the polysulfides, 3Parts 1 and 2. cf.14) and 10).. Dipole moments of poly(trimethylene sulfide) and comparisons between some polysulfides and the corresponding polyoxides (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 2573-2581 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Conformational energy calculations indicate that poly(trimethylene sulfide) (P3MS) approximates the idealized freely-rotating chain in that gauche-trans energy differences in this molecule are very small. This occurs because the relatively long S—C bond tends to relieve congestion within the P3MS chain. The bonds in poly(trimethylene oxide) (P3MO) are much more constrained to a particular rotational state because the O—C bond is shorter than the S—C one, and in this sense P3MO is considerably less flexible. In this study the dipole moments 〈μ2〉0 of P3MS are measured as a function of temperature, and the results analyzed in terms of the rotational isomeric-state theory. Using conformational energies derived from semiempirical potential energy functions, a three-rotational-state model gave values of the dipole moment in good agreement with experiment. Theoretical and experimental values of the temperature coefficient of 〈μ2〉0 were in disagreement, however, and a five-rotational-state model based on that adopted by Flory in a similar study of polymethylene failed to remove this discrepancy. Some statistical properties are tabulated for the n-alkylene polysulfides studied to date and for structurally related polyoxides. In these types of molecules, strong preferences for pairs of gauche states in CH2S—CH2—SCH2 and CH2 O—CH2—OCH2 sequences give rise to unusually small values of the dipole moment.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1982.021831027
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  • 9
    Electronic Resource
    Electronic Resource
    The effects of various catalysts in the in-situ precipitation of reinforcing silica in polydimethylsiloxane networks (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 185 (1984), S. 2609-2617 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A variety of inorganic and organic acids, bases, and salts were studied as catalysts for the hydrolysis of tetraethyl orthosilicate, the reaction previously employed for the precipitation of silica within already-cured elastomeric networks of polydimethylsiloxane. These substances were compared with regard to the amount of silica precipitated at room temperature, and the extent of reinforcement as judged by the upturns in the stress-strain isotherms at high elongations. On this basis, the acids were the least effective and the salts the most effective.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.021851212
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  • 10
    Electronic Resource
    Electronic Resource
    Some spectroscopic evidence on deformation mechanisms in elastomeric networks at very high elongations (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 499-506 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Bimodal elastomeric networks are unusually tough materials in that they generally show large increases in modulus at high elongations. In the present study such networks were prepared by end-linking mixtures of very short and relatively long chains of poly(dimethylsiloxane) (PDMS) [—Si(CH3)2O—]n, which is known to have easily deformable Si—O—Si bonds. Their stress-strain isotherms were then determined in order to locate the range of elongations over which the upturns were most pronounced. Raman and infrared spectra were then obtained in this range using both a double monochromator Raman spectrophotometer and a Fourier transform infrared spectrophotometer with attenuated total reflection. The elongations imposed were found to cause small but not negligible frequency shifts for the stretching and bending modes of the Si—O—Si backbone. These shifts are probably due to rotational isomerization of the PDMS skeletal bonds, but there could also be a small contribution from bond-angle deformations. The results thus support the usual assumption that the increases in modulus observed for bimodal networks are primarily due to the very limited number of spatial configurations available to the short network chains, particularly in the case of chains having skeletal bonds that are less easily deformed than those in PDMS.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920303
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