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  • Polymer and Materials Science  (23)
  • ASTROPHYSICS  (21)
  • Astrophysics  (9)
  • 1995-1999  (15)
  • 1990-1994  (26)
  • 1975-1979  (6)
  • 1960-1964  (6)
Collection
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 178 (1977), S. 465-474 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A systematic study of the effect of potassium hydroxide on the autoxidation of poly(propylene oxide)s with number average molecular weights, M̄n, in the range 400-3000 has been made in the range of temperature 110-140°C. For all the polymers a considerable increase in the induction time was produced by KOH in solution in the polymer, the increase being most marked for the polymer of lowest molecular weight. For the polymers of molecular weight 1000 and lower, the rate of the subsequent autoxidation was considerably reduced by the KOH, the effect being greatest for the polymer of molecular weight 400. For polymers of molecular weight 2000 and above no change in rate was observed. The effectiveness of KOH as an antioxidant is shown to depend on the concentration of terminal hydroxyl groups and is explained by the non-radical decomposition of RO-2 ions.
    Additional Material: 5 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 3099-3109 
    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: A series of six Hytrel/PVC blends were prepared by solution blending Hytrel in methylene chloride and PVC in tetrahydrofuran. The samples were subsequently prepared in sheet form by hot pressing at 170°C. Physical and mechanical properties of the homopolymers and the blends were investigated. The copolyester homopolymer is a partly crystalline elastomeric material. The level of crystallinity was measured by x-ray diffraction and the sensitivity of this level to heat treatments and quenching determined by DSC. A Morgan pulse propagation meter was used to measure sonic velocity and, indirectly, acoustic impedance of the blends. Dynamic mechanical studies indicated that blends containing 25%-50% by weight of Hytrel were completely compatible in the sense that a single glass transition was observed; but as the Hytrel level was increased to 60% and 65%, a shoulder became apparent on the low-temperature side of the glass transition peak. At 80% Hytrel, two peaks were observed, indicating incompatibility. The glass transition temperatures of these blends were found to decrease linearly with added Hytrel.
    Additional Material: 9 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 5 (1961), S. 580-588 
    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: Torsional modulus-temperature data have been obtained on heterogeneous polymer compositions prepared by several procedures. Both the state of aggregation of the component chain molecules and their degree of compatibility are significant variables. Modulus curves similar to those for crystalline polymers can be obtained from incompatible polymers having glass temperatures sufficiently far apart. Detailed interpretations are presented for modulus curves of both individual homopolymers and bicomponent heterogeneous polymer mixtures.
    Additional Material: 8 Ill.
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  • 4
    ISSN: 0887-624X
    Keywords: oligocyclosiloxanes ; hydrosilation ; heptamethylcyclotetrasiloxane ; siloxane redistribution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of oligocyclosiloxanes via hydrosilation reactions has been investigated. Hydrosilation reactions employing heptamethylcyclotetrasiloxane and vinyl-containing silanes and siloxanes yielded a variety of oligocyclosiloxanes with various numbers of cyclosiloxane rings connected through tri-, tetra-, penta-, hexa-, hepta-, or octafunctional junctions. The oligocyclosiloxanes were characterized by gas chromatography, IR spectroscopy, 29Si-, 1H-, and 13C-NMR spectroscopy, elemental analysis, and vapor phase osmometry. The polycyclics were redistributed with hexamethyldisiloxane and the resulting fragments analyzed by gas chromatography. All results were consistent with the formation of isomeric oligocyclosiloxanes due to a lack of absolute regioselectivity of the hydrosilation reaction. © 1993 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 5
    ISSN: 0006-3525
    Keywords: AIDS ; DNA structure ; polymerase structure ; protein - DNA interaction ; x-ray crystallography ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of the DNA and the interactions of the nucleic acid with the protein in a complex of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) and a 19-mer/18-mer double-stranded DNA template-primer (dsDNA) are described. The structure of this HIV-1 RT complex with dsDNA serves as a useful paradigm for studying aspects of nucleotide polymerases such as catalysis, fidelity, drug inhibition, and drug resistance. The bound dsDNA has a bend of approximately 41° at the junction of an A-form region (first five base pairs near the polymerase active site) and a B-form region (the last nine base pairs toward the RNase H active site). The 41° bend occurs smoothly over the four base pairs between the A-form portion and the B-form portion in the vicinity of helices αH and αI of the p66 thumb subdomain. The interactions between the dsDNA and protein primarily involve the sugar - phosphate backbone of the nucleic acid and structural elements of the palm, thumb, and RNase H of p66, and are not sequence specific. Amino acid residues from the polymerase active site region, including amino acid residues of the conserved Tyr-Met-Asp-Asp (YMDD) motif and the “primer grip,” interact with 3′-terminal nucleotides of the primer strand and are involved in positioning the primer terminal nucleotide and its 3′-OH group at the polymerase active site. Amino acid residues of the “template grip” have close contacts with the template strand and aid in positioning the template strand near the polymerase active site. Helix αH of the p66 thumb is partly inserted into the minor groove of the dsDNA and helix αI is directly adjacent to the backbone of the template strand. Amino acid residues of Β1′, αA′, αB′, and the loop containing His539 of the RNase H domain interact with the primer strand of the dsDNA. © 1997 John Wiley & Sons, Inc. Biopoly 44: 125-138, 1997
    Additional Material: 8 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 5 (1961), S. 337-348 
    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: The predicted general incompatibility of mixtures of polymers has been further confirmed. Thirty-one mixtures of homopolymer pairs showed phase separation in a common solvent. These included closely related polymers such as polyacrylates with both polymethacrylates and other polyacrylates and pairs of different polymethacrylates. Typical immiscible combinations are PMA/PEA and PEMA and PEMA/PMMA. It was also found that the presence of a common monomer constituent did not result in complete compatibility of either a homopolymer with a copolymer or a mixture of two copolymers. Apparently, none of the combinations tried were sufficiently similar to result in heats of interaction small enough to be counteracted by the small entropy change involved. Since another possibility for attaining miscibility is through polar interactions, the effects of ionic and hydrogen-bonding substituents upon polymer-polymer compatibility were considered, and selected experiments were done on a series of carboxyl-containing polymers and their sodium salts. It was concluded that hydrogen bridging occurs preferentially either intramolecularly or between polymer and solvent rather than between two different types of chains each having hydrogen-bonding ability. Thus, poly(acrylic acid) and poly(methacrylic acid) show two-phase separation in water. Although poly(sodium acrylate) and poly(sodium methacrylate) are completely miscible, mixtures of the partially neutralized acids, e.g., PAA and PNaMA mixtures, show separation. In contrast to predictions for less polar polymers, compatibility of mixtures of polymers containing high mole fractions of carboxylic acid monomers showed a pronounced dependence upon solvent. Thus, the two copolymers 45/53 EA-MAA and 47/53 MMA-MAA are incompatible in methanol or ethanol but form homogeneous solutions in DMF or DMS.
    Additional Material: 1 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 999-1004 
    ISSN: 0887-6266
    Keywords: latex ; polystyrene ; luminescence ; particle ; micron-diameter ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A technique for rapid determination of the presence of polystyrene in individual micron-diameter polymer particles of mixed composition is presented. This technique is based upon observation of visible emission from conjugated regions of the polymer backbone, generated photochemically, while the particle is held in an optical trap. Particle emission characteristics are dependent upon particle size and suspending solvent. Emission spectra are provided for single component polystyrene particles and mixed polymer particles containing poly(methyl methacrylate), poly(N-vinyl pyrrolidone), and polystyrene. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 999-1004, 1998
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 485-496 
    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: A new route (“direct forming”) was developed for forming dense PBI shapes from PBI powder. The new process affords the possibility of automated PBI powder shaping (“cold compaction”) and densification in batches of multiple parts by a “powder-assisted hot isostatic pressing” process. Direct forming is a more productive alternative to hot compression molding. Two developments enable PBI direct forming: (1) the discovery that PBI powders that are porous and plasticized with moisture can be shaped by compaction at ambient temperatures (cold-compacted), and (2) a finding that cold-compacted shapes can be densified in large batches by a powder-assisted hot isostatic pressing. The porous PBI powder is formed from PBI in solution by a spray-precipitation process. When plasticized with moisture, this powder is cold-compactible to PBI shapes with densities up to 94% of that of ultimate density of PBI. These shapes, which have sufficient strength to be handled, are then further consolidated via powder-assisted hot isostatic pressing to shapes with excellent thermal and mechanical properties and densities of about 99% of the ultimate. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 9
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The need for alternatives to autogenous bone grafts is widely recognized. This study compared the torsional strength of canine femora 1 year after grafting with one of three forms of a collagen/hydroxyapatite/tricalcium phosphate bone grafting material (COLLAGRAFT15), autogenous bone, or no graft. The groups were compared to each other and to the unoperated contralateral femora. Results of torsional testing were evaluated for torsional strength, torsional displacement, total energy to fracture and White fracture mode. Data analysis showed lower torsional strength of the operated vs. unoperated femora with the exception of morsellized COLLAGRAFT15 material, which had higher strength. However, the only difference in the operated groups was that the morsellized COLLAGRAFT15 had greater strength than several groups including the autogenous bone group. There was no difference found in angular displacement between any of the groups. However, there was a difference in the energy to fracture in both strip forms of the COLLAGRAFT15. The final conclusion is that in this model, grafting with COLLAGRAFT15 provided torsional properties at one year postoperatively at least equivalent to autogenous bone. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 7 (1963), S. 59-69 
    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: The isolation of two graft copolymers of styrene on polyethyl acrylate from the ungrafted homopolymers by solvent extraction procedures is discussed. For the grafts and their corresponding mixtures ηsp/c versus c plots were determined, and no anomalies were observed. Qualitative data on the solubilities and phase properties of the grafts are given. Torsional modulus-temperature curves are shown for graft copolymer and the individual homopolymers.
    Additional Material: 2 Ill.
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