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  • Articles  (17,923)
  • Springer  (13,618)
  • American Chemical Society  (4,305)
  • 1995-1999  (17,923)
  • 1997  (17,923)
  • Physics  (17,923)
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  • Articles  (17,923)
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  • 1995-1999  (17,923)
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  • 1
    Electronic Resource
    Electronic Resource
    Effect of Ca doping on the structural and superconducting properties of EuBaSrCu3O7−δ (1997)
    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 645-647 
    Details
    ISSN: 1557-1947
    Keywords: EuBaSrCu3O7−δ superconductor ; Ca doping ; orthorhombicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The effect of Ca doping in EuBaSrCu3O7−δ has been investigated by X-ray diffraction, ac susceptibility, and electrical resistivity measurements. X-Ray diffraction analyses of the samples showed that up to 30 at.% Ca can be substituted for Sr in EuBaSrCu3O7−δ, which has orthorhombic symmetry. The orthorhombicity decreases with increase inx, in EuBaSr1−xCax Cu3O7−δ, the material becoming tetragonal atx=0.2. Ac susceptibility and dc electrical resistivity measurements as function of temperature from 10 to 300 K showed that the superconducting transition temperatureT c decreases monotonically from 84 to 75K as the Ca concentrationx increases from 0.0 to 0.3 The decrease inT c can be attributed to the structural change taking place in EuBaSrCu3O7 as a consequence of replacement of Sr by Ca.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02471926
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  • 2
    Electronic Resource
    Electronic Resource
    New research opportunities in superconductivity IV (1997)
    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 583-621 
    Details
    ISSN: 1557-1947
    Keywords: Superconductivity ; research opportunities ; state of the art
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract This report surveys the considerable progress made over the last five years—such as the marketing of superconducting quantum interference devices (SQUIDs), cellular wireless filter systems, and high current leads—and assesses needs and opportunities in the areas of fundamental science, materials development, thin film and device applications, and wire and bulk applications. It examines the challenges facing high-temperature superconductivity: from the need to understand the mechanism of high-temperature superconductivity and the unusual “normal” state to the need for new instrumentation for material characterization. Advances in thin film and bulk materials are reviewed, and obstacles impeding the commercialization of HTS materials are examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02471924
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  • 3
    Electronic Resource
    Electronic Resource
    High-resolution electron microscopy and low-temperature electron diffraction studies of a Bi2212 single crystal grown by the floating zone method (1997)
    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 649-655 
    Details
    ISSN: 1557-1947
    Keywords: Single crystal of Bi2Sr2CaCu2O8 ; high-resolution electron microscopy ; low-temperature electron diffraction ; lattice anomaly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract High-resolution electron microscopy of a Bi2Sr2CaCu2O8 (Bi2212) single crystal prepared by the floating zone method shows that the single crystal is of high quality; there is no intergrowth faulting in the layered structure along thec-axis. Low-temperature selected area diffraction and convergent beam electron diffraction (CBED) studies of this high-quality single crystal show that there is no detectable change for both the point group symmetry of the basic structure and the modulated structure from room temperature to about 15 K. However, a lattice anomaly around 215 K was suggested by measuring the temperature dependence of the ratio between the cross-point distances of the HOLZ lines in high-index CBED patterns. The presence of the lattice anomaly was further confirmed by low-temperature X-ray diffraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02471927
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  • 4
    Electronic Resource
    Electronic Resource
    The crystal field in rare earth based high-temperature superconductors (1997)
    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 623-643 
    Details
    ISSN: 1557-1947
    Keywords: Superconductivity ; crystal field ; rare earth ; relaxation ; gap symmetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Neutron spectroscopy is a powerful tool to determine unambiguously the crystal-field (CF) potential in rare-earth (R) based high-T c superconducting materials. This technique provides detailed information on the electronic ground state of the R ions which is important to understand the thermodynamic magnetic properties as well as the observed coexistence between superconductivity and long-range magnetic ordering of the R ion sublattice at low temperatures. Moreover, the decay of the antiferromagnetic state of the parent compound as well as the evolution of the superconducting state upon doping can be directly and quantitatively monitored. It is found that the observed CF spectra separate into different local components whose spectral weights distinctly depend on the doping level, i.e., there is clear experimental evidence for cluster formation. The onset of superconductivity can be shown to result from percolation which means that the superconductivity is an inhomogeneous materials property. Since the linewidths of CF transitions directly probe the static electronic susceptibility, we discuss temperature-dependent experiments of the relaxation rate of CF excitations in both optimally doped and underdoped regimes. It is shown that there is clear evidence for the opening of an electronic gap in the normal state of underdoped superconductors. Furthermore, the relaxation behavior appears to be extremely dependent upon the energy at which the static susceptibility is being probed. The main observed features can be reproduced by considering a strongly anisotropic gap function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02471925
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  • 5
    Electronic Resource
    Electronic Resource
    The effects of cobalt substitution on the thermal diffusivity of YBa2Cu3O7−δ superconductor (1997)
    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 663-668 
    Details
    ISSN: 1557-1947
    Keywords: Thermal diffusivity ; acoustic plasmons ; cobalt substitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The thermal diffusivity κ(T) of the cobalt-substituted sintered YBCO system, YBa2Cu3−x Co x O7∮δ (x=0.0, 0.1), has been measured to, investigate, effects of atomic substitution and charge carrier concentration on the thermal diffusion processes. The thermal diffusivity was measured in the temperature range 35–300 K, using the transient-plane-source technique. The results show that, belowT c , the κ(T) values of the doped (x=0.1), samples are lower than the corresponding values for the undoped (x=0.0) samples. This may be due to the difference in the free-charge carrier concentrations of the two samples. A decoupling between the conducting Cu−O planes as a result, of Co-doping in the chain sites may contribute to additional decrease in the thermal diffusivity of the doped sample. An attempt was made to explain the rise in the thermal diffusivity belowT c by adopting a recent theoretical model based on the existence of weakly damped collective electron excitations of Bose type, with acoustic dispersion relation, (acoustic plasmons) inside the superconducting gap.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02471929
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  • 6
    Electronic Resource
    Electronic Resource
    Intrinsic surface depression of the order parameter under mixed (s+id)-wave pair symmetry and its effect on the critical current of high-T c SIS Josephson junctions (1997)
    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 657-662 
    Details
    ISSN: 1557-1947
    Keywords: High-T c superconductors ; order parameter ; Josephson junctions ; Josephson critical current ; pair symmetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An intrinsic gap depression at the superconductor-insulator interface due to the very short value of the coherence length in high-T c superconductors [HTS] is considered in the framework of a mixed (s+id)-wave pair symmetry for the order parameter ranging from pures to pured-wave. This gap depression acts as the main physical agent causing the relevant reduction ofI c (T)R n (T) values with respect to BCS expectations in HTS SIS Josephson junctions. Good agreement with various experimental data is obtained with both pures-wave and pured-wave symmetries of the order parameter, but with amounts of gap depression depending on the pair symmetry adopted. Regardless of the apir symmetry considered, these results prove the importance of the surface order-parameter depression in the correct interpretation of theI c (T)R n (T) data in HTS SIS junctions. In the case of a planar YBCO-based junction the use of the de Gennes condition allowed us to tentatively obtain an upper limit for the amount ofd-wave present in the gap of YBCO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02471928
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  • 7
    Electronic Resource
    Electronic Resource
    An equation of state of high-temperature superconductor (1997)
    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 669-672 
    Details
    ISSN: 1557-1947
    Keywords: Equation of state ; bulk modulus ; cohesive energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In the present paper the expression of cohesive energy and the bulk modulus as a function of volume are formulated for high-T c copper oxide superconductors. The model employed consists of long-range electrostatic Coulomb interaction and short-range overlap repulsion. The short-range overlap potential is considered in the Born-Landé inverse power form. The model, parameters of the Born-Landé model are calculated from the equilibrium condition and data of bulk modulus at room temperature. The computed values of pressure derivatives of bulk modulus atP=0 and the values of bulk modulus are found to be in very close agreement with experimental values for high-T c copper oxide and their nonsuperconducting parent compounds. It is also found that the quantity ΔU/U(V o) of these compounds increases with increasing hydrostistic pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02471930
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  • 8
    Electronic Resource
    Electronic Resource
    Van hove singularity and “pseudo-gap” in HTSC (1997)
    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 673-675 
    Details
    ISSN: 1557-1947
    Keywords: Cuprates ; van Hove singularity ; pseudo-gap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Several experimental features in the normal state of cuprates have been interpreted using a “pseudogap”. We show that these results may be explained by the band structure of the CuO2 planes in the metallic region, which exhibits, saddle points (van Hove singularities).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02471931
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  • 9
    Electronic Resource
    Electronic Resource
    Dehydrogenative polycondensation of telechelically bis(dimethylsilyl)functionalized oligo(dimethylsiloxane)s or aromatics and 1,3,3,5,5,7,7,7-octamethyltetrasiloxane (1997)
    Springer
    Polymer bulletin 38 (1997), S. 1-5 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Telechelically bis(hydrodimethylsilyl)-functionalized oligo(dimethylsiloxane)s or aromatics were found to give polymers constituting of alternating disilylene and oligodimethylsiloxane or 4,4′-diylaromatics as repeating units by dehydrogenative coupling reaction in the presence of palladium dibenzylideneacetone complex. The same catalyst gave polysilylenes with trisiloxane pendant from 1,1-dihydro-1,3,3,5,5,7,7,7-octamethyltetrasiloxane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050011
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of polyorganosiloxane particles (1997)
    Springer
    Polymer bulletin 38 (1997), S. 23-25 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Hybrid particles have been synthesized from methyltriethoxysilane (MTEOS) by the sol-gel process. The particle size, size distribution, particle surface morphology conductivity and pH of the reaction solution at different reaction times were determined. Compared with tetraethyl orthosilicate (TEOS) and p-(chloromethyl)phenyl-trimethoxysilane (CMPTOS), MTEOS has a slower hydrolysis rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050014
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  • 11
    Electronic Resource
    Electronic Resource
    Polymerization of 4-n-alkylstyrenes with typical Ziegler-Natta and metallocene catalysts (1997)
    Springer
    Polymer bulletin 38 (1997), S. 43-48 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Polymerization of 4-n-alkylstyrenes (alkyl side group; methyl, ethyl, propyl and buthyl) was carried out with the η-C5(CH3)5TiCl3-methylaluminoxane (MAO) and TiCl3-triethylaluminum (TEA) catalyst systems. When the η-C5(CH3)5TiCl3-MAO catalyst was used, the stereoregularity of resulting polymers markedly depended on the length of substituted alkyl groups, i.e., the catalyst gave highly syndiotactic poly(4-methylstyrene), but produced atactic polymers for the monomers with ethyl, propyl and buthyl substituents. On the other hand, all the poly(4-n-alkylstyrene)s obtained with the TiCl3-TEA catalyst were highly isotactic. As a result, a large difference was observed in the thermal properties of polymers obtained between the two catalyst systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050017
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  • 12
    Electronic Resource
    Electronic Resource
    Enzyme-catalyzed peptide syntheses in aqueous polymer two-phase systems (1997)
    Springer
    Polymer bulletin 38 (1997), S. 49-53 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Peptide synthesis in the aqueous polymer two-phase system was examined. Water soluble polymers adopted were dextran and polyethyleneglycol (PEG). By the modification of a proteolytic enzyme, trypsin, with dextran carrying a very small number of carboxyl groups, a separation of the enzyme from its peptide product, N-benzoyl-L-arginine glycinamide, which is relatively more soluble in a PEG phase could be realized. This separation drastically reduced a so-called "mass-law" effect, and increased the yield of the reaction product. The aqueous polymer two-phase system would be useful to enhance the usefulness of biocatalysts in organic syntheses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050018
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  • 13
    Electronic Resource
    Electronic Resource
    Effect of the crosslinking with 1,1,1-trimethylolpropane trimethacrylate on 5-fluorouracil release from poly(2-hydroxyethyl methacrylate) hydrogels (1997)
    Springer
    Polymer bulletin 38 (1997), S. 55-62 
    Details
    ISSN: 1436-2449
    Keywords: Key words: Poly(2-hydroxyethyl methacrylate) (PHEMA) – 5-fluorouracil (5-FU) – 1,1,1-trimethylolpropane trimethacrylate (TPT) – hydrogel – controlled release – diffusion coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The aim of this study is to examine the influence of crosslinking density on 5-Fluorouracil release from poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels crosslinked with 1,1,1-trimethylolpropane trimethacrylate (TPT). PHEMA hydrogels were synthesized by bulk polymerization with different proportions of TPT (1 – 10 wt%) as crosslinker agent and ammonium persulphate as initiator, enabling polymerization in the feed mixture in the presence of water. As a result, 5-FU could be trapped by including it as a sodium salt in the feed mixture of polymerization. Discs with 5-FU loads between 1 – 16 mg/disc were obtained. Swelling and 5-FU release kinetics studies were carried out in saline solution at 310 K. The diffusion studies were in accordance with Fick's second law during the initial stages, enabling the diffusion coefficients of the process to be determined. The time required for discs to reach total 5-FU release was between 35 h and 160 h and was a function of crosslinking density of the gels and 5-FU load of the discs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050019
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  • 14
    Electronic Resource
    Electronic Resource
    Effect of surfactant concentration, pH, and shear rate on the rheological properties of aqueous systems of a hydrophobically modified chitosan and its unmodified analogue (1997)
    Springer
    Polymer bulletin 38 (1997), S. 71-79 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Oscillatory shear, shear relaxation and viscosity experiments have been carried out on semidilute solutions of chitosan and on a hydrophobically modified analogue (HM-chitosan) in 1% acetic acid. This was done in the presence of various amounts of cetyltrimethylammonium bromide (CTAB) and at different pH values. All the rheological measurements on the HM-chitosan solutions revealed significant polymer-surfactant interaction and pH effects. The observed rheological effects were least pronounced at pH ≈ 4, while a strong viscoelastic response was found at pH values of 1 and 5 in HM-chitosan solutions of low surfactant concentration. At these conditions, significant shear-thinning effects were observed. In semidilute solutions of unmodified chitosan, the influence of pH, surfactant concentration and shear rate on the rheological properties was moderate or insignificant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050021
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  • 15
    Electronic Resource
    Electronic Resource
    Electrical conductivity of polystyrene/styrene-butadiene block copolymer blends containing carbon black (1997)
    Springer
    Polymer bulletin 38 (1997), S. 95-100 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The electrical resistivity and mechanical properties of carbon black (CB)-filled polystyrene (PS)/styrene-butadiene block copolymer (SB) blends have been studied. Good electrical performance was achieved with pure SB and PS/SB blends indicating an inhomogeneity of these materials and the heterogeneous micro-dispersion of the CB particles. The percolation threshold of the filler inside SB or PS/SB blends is around 3.6 wt%, which is lower than that expected for incompatible PS/PBD blend. The addition of small amount CB decreases the elongation at break of PS/SB blends indicating some disturbance at the interface of these compatible material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050024
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  • 16
    Electronic Resource
    Electronic Resource
    Homo-, co- and terpolymerization of 1,5-hexadiene using a methylalumoxane activated mono-Cp-amido-complex (1997)
    Springer
    Polymer bulletin 38 (1997), S. 141-148 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Homo- and copolymerizations of 1,5-hexadiene with ethene and styrene using halfsandwich metallocene catalyst Me2Si(Me4Cp)(N-tert.-butyl)TiCl2/MAO (Cp = cyclopentadienyl, Me = methyl, MAO = methylalumoxane) were investigated. According to 13C-NMR spectroscopic microstructure analysis, cyclopolymerization of 1,5-hexadiene afforded randomly distributed cis- and trans-cyclopentane rings in the homo- and copolymer backbone. 1,5-hexadiene incorporation reached 52 mol-%. The ratio of vinyl side chains to cyclopentane rings was controlled by 1,5-hexadiene concentration, where low 1,5-hexadiene concentration promoted cyclopolymerization. Copolymer glass transition temperatures increased with increasing content of cyclic units in the backbone. Styrene was used successfully as termonomer in ethene/1,5-hexadiene polymerization, resulting in a semicrystalline terpolymer with cyclic and styrenic units in the polymer backbone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050030
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  • 17
    Electronic Resource
    Electronic Resource
    Synthesis and properties of polyurethanes containing phosphatidylcholine analogues in the main chains and long-chain alkyl groups in the side chains (1997)
    Springer
    Polymer bulletin 38 (1997), S. 133-140 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. New phospholipid polyurethanes containing phosphatidylcholine analogues in the main chains and octyl or oleyl groups in the side chains were synthesized by the addition polymerization of diols, bis[2-(2-hydroxyethyldimethylammonio)ethyl]2-octyl-1,3-propanediphosphate or bis[2-(2-hydroxyethyldimethylammonio)ethyl]2-oleyl-1,3-propanediphosphate, with diisocyanates such as 4,4′-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), and 2,4-tolylene diisocyanate (TDI). The new phospholipid diols and polyurethanes were characterized by their IR and 1H-NMR spectral data and elemental analysis. The new phospholipid polyurethanes exhibit common polyelectrolyte viscosity behaviours revealed by viscosity measurements. Moreover, π-A isotherms for these polyurethanes were also prepared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050029
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  • 18
    Electronic Resource
    Electronic Resource
    Photoinitiated cationic ring-opening polymerization of a cyclosiloxane (1997)
    Springer
    Polymer bulletin 38 (1997), S. 165-168 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Hexamethylcyclotrisiloxane was found to undergo photoinitiated cationic ring-opening polymerization in solution and bulk, upon exposure to UV radiation, in the presence of either sulfonium or iodonium salts or an iminosulfonate derivative. Glass transition temperatures were below − 100 °C. Molecular weights, determined by size exclusion chromatography relative to polystyrene standards, increased with photolysis lamp intensity. Use of an iodonium photoinitiator afforded poly(dimethylsiloxane) with Mn = 172,000. Polymerization of hexamethylcyclotrisiloxane was accompanied by a small increase in volume (3 – 4%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050033
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  • 19
    Electronic Resource
    Electronic Resource
    An alternating copolymer for a blue light-emitting diode (1997)
    Springer
    Polymer bulletin 38 (1997), S. 169-176 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. An alternating copolymer composed of 9,9′-dihexylfluorene and N-2-ethylhexyl carbazole was synthesized to use as an emissive polymer in a light-emitting diode (LED). The copolymer is soluble in organic solvents and spin-cast to make a fine film. An LED fabricated by sandwiching the alternating copolymer between indium-tin oxide and aluminum emits a white color with the full width at half maximum of 150 nm. The electroluminescence spectrum becomes simplified to have an emission peak at 460 nm for fine blue color when the copolymer is blended with poly(vinylcarbazole) with a ratio of 1 to 4 before the use as an emissive layer. The forward bias turn-on voltage for the LED is 13, and quantum efficiency is 0.002%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050034
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  • 20
    Electronic Resource
    Electronic Resource
    IR study of hydrogen bonding in novel liquid crystalline epoxy/DGEBA blends (1997)
    Springer
    Polymer bulletin 38 (1997), S. 439-445 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The hydrogen bonding of LCE/DGEBA blend was studied using FT-IR. IR spectra of hydroxyl region and carbonyl region were investigated according to the content of LCE. IR spectra of LCE/DGEBA blend before and after curing were compared. Most hydroxyl group in DGEBA rich blends formed intermolecular or intramolecular hydrogen bonding after curing, while free hydroxyl group was present in LCE rich blends. Intramolecular hydrogen bonding was popular in DGEBA rich blends due to the conformational reason. Most carbonyl group was hydrogen bonded with hydroxyl or amine group after curing and the fraction of hydrogen bonded carbonyl was high in DGEBA rich blends.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050071
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  • 21
    Electronic Resource
    Electronic Resource
    A route to polysiloxanes with pendant imidazole groups Hydrosilylation of N-allylimidazole hydrochloride with methyldichlorosilane (1997)
    Springer
    Polymer bulletin 38 (1997), S. 371-378 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Hydrosilylation of N-allylimidazole hydrochloride by methyldichlorosilane (MeCl2SiH) under mild conditions leads to a high yield of N-[γ-(methyldichlorosilyl)propyl]imidazole hydrochloride – highly reactive monomer for synthesis of imidazole modified polysiloxanes. This compound was used as the substrate for the generation of new cyclooligosiloxanes with the imidazole group attached through the trimethylene bridge to a siloxane ring. The anionic ring-opening polymerization of these cyclics permits the controlled synthesis of polysiloxanes with imidazole groups pendant to the polymer chain.
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    URL: http://dx.doi.org/10.1007/s002890050062
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  • 22
    Electronic Resource
    Electronic Resource
    Novel aprotic polar polymers 1. Synthesis of aliphatic polysulfoxides (1997)
    Springer
    Polymer bulletin 38 (1997), S. 379-386 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Aliphatic polysulfoxides having sulfoxide groups in the main chain were prepared by the selective oxidation of aliphatic polysulfides using aqueous hydrogen peroxide in chloroform. Degree of oxidation to sulfoxides was calculated from the integral ratios of methylene protons adjacent to sulfur atoms in 1H-NMR spectra. Poly(hexamethylene sulfoxide) was subjected to Swern oxidation of primary or secondary alcohols, in which 1-octanol and 6-undecanol were oxidized to give octanal and 6-undecanone, respectively, in quantitative yields.
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    Electrical conductivity in iodine-doped nonconjugated polyanilinefurfural (1997)
    Springer
    Polymer bulletin 38 (1997), S. 573-577 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Polyanilinefurfural (PAF) has been prepared. Its chain contains aromatic and furan rings, but the backbone is nonconjugated. However, when treatment with iodine, the color of PAF turns metallic black, and PAF becomes electrically conductive. The electrical conductivity of I2-doped PAF can reach 10−3 S ⋅ cm−1 which is more than 10 orders of magnitude higher than what was observed at the pristine state. The effects of iodine content on the conductivity of PAF and the conductivity stability were investigated. FTIR spectra, U.v./vis absorption spectra, E.s.r. measurement and X.p.s. measurement of the undoped and doped PAF were studied. This paper will demonstrate that: if given appropriate substituents and dopants, significant charge transfer may be expected even for nonconjugated polymers and it may display electronic conductivity to a certain level.
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    Factor analysis in the NMR characterization of multicomponent polymers (1997)
    Springer
    Polymer bulletin 38 (1997), S. 555-562 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Factor analysis has been found to be suitable for the analysis NMR data of polymers which contain multiple components. Two series of ethylene/propylene copolymers have been studied by this technique. In general, the number of components that can be resolved from NMR data depends on both the quality and the quantity of available experimental data.
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    The role of complex formation in the anionic polymerization of l-lactide (1997)
    Springer
    Polymer bulletin 38 (1997), S. 609-612 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The rate lowering effect of crown ethers in the anionic polymerization of l-lactide is interpreted by the formation of activated monomer-cation complex. This interpretation is supported by molecular mechanics calculations. The formation of a 1 : 1 complex between lithium ion and l-lactide in THF was proved by 1H NMR and the formation constant was measured to be 3.8 M−1.
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    Application of a statistical method to study the spherulitic growth of polymer blends (1997)
    Springer
    Polymer bulletin 38 (1997), S. 601-608 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. This paper has two objectives. Firstly, to plan experimental blends (based on PVDF, PMMA and PVA) according to a statistical method proposed by Scheffé and subsequently to apply the model to the study of the spherulitic growth of PVDF with the aim of assess its suitability. In case it proved adequate, a simple method would become for the design of new materials from the polymer under study.
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    An investigation into the synthesis of polycarbazole squaraine derivatives (1997)
    Springer
    Polymer bulletin 38 (1997), S. 493-499 
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    Notes: Abstract. The polycondensation of squaric acid with 1,2-(9-Ethylcarbazol-3-yl)ethene and N-ethyliminostilbene in polyphosphoric acid yielded insoluble polymers which included substituted phosphate groups on the phenyl rings. The presence of phosphorus in these polymers was identified using solid-state 31P NMR and EDAX techniques. Furthermore the phosphate groups were not ionic, hence no charge-balancing anions were present. Both polymers did not electrically conduct but exhibited dielectric breakdown values of 0.1 and 0.06 MV cm−1 respectively.
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    Comparative study on the lamellar crystal structure of high and low density polyethylenes (1997)
    Springer
    Polymer bulletin 38 (1997), S. 707-714 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. A comparative study was undertaken on well characterized HDPE and LDPE samples in order to obtain a better understanding of the morphology of the crystalline phase. Thickness of the lamellae was determined by WAXS. The melting points were calculated by empirical and Gibbs-Thomson equations, considering either folded or extended chains, and compared to DSC data. The results confirm that in HDPE the chains are folded, the segment between folds containing about 100 carbon atoms, while in LDPE, the chains are extended, with segments of about 73 carbon atoms in the crystalline core, linked to the paracrystalline layer and amorphous zones, which contain long folds and chain ends, as proposed in the 3-phase model by Vile et al.
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    The synthesis and thermotropic liquid crystalline behavior of the novel poly(aryl ether ketone)s containing chloro-side group (1997)
    Springer
    Polymer bulletin 38 (1997), S. 621-625 
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    Notes: Abstract. The novel poly(aryl ether ketone)s containing chloro-side group were synthesized by nucleophilic substitution reactions of 4,4′-biphenol and chlorohydroquinone with either 4,4′-difluorobenzophenone (BP/CH/DF) or 1,4-bis(p-fluorobenzoyl)benzene (BP/CH/BF) and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. The thermotropic liquid crystalline behavior was observed in the copolymers containing 50 and 70% biphenol. Melting transition (Tm) and isotropization transition (Ti) both appeared in the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline state. The novel poly(aryl ether ketone)s had relatively higher glass transition temperature (Tg) in the range of 168 ∼ 200 °C and lower melting temperature (Tm) in the range of 290 ∼ 340 °C. The thermal stability (Td) was in the range of 430 ∼ 490 °C.
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    Synthesis and characterization of wholly aromatic polyamides containing pendent amino and cyano groups (1997)
    Springer
    Polymer bulletin 38 (1997), S. 635-642 
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    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract. The new pyrazole-ring containing diamine monomer with amino and cyano groups, 1,3-di-p-aminophenyl-4-cyano-5-aminopyrazole (PYA), was prepared from 4-nitrobenzoyl chloride and 4-nitrophenyl hydrazine with 4 steps. The monomer was converted to polyamides with terephthaloyl chloride and isophthaloyl chloride. The amino and cyano groups on the pyrazole-ring were not affected during polymerization. The synthesized polyamides having intrinsic viscosities of 0.92 – 1.18 dL/g were amorphous, and soluble in polar aprotic solvents and boiling acetone and THF. The polymers had high glass transition temperatures and high thermal stability. 5% weight loss temperatures in nitrogen occurred around 490 °C, but these polymers are partially degraded at 300 °C in air due to the amino group on the pyrazole-ring.
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    On-line HPLC 1H NMR coupling for the analysis of fatty alcohol ethoxylates (1997)
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    Polymer bulletin 38 (1997), S. 673-679 
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    Notes: Abstract. The characterisation of fatty alcohol ethoxylate based surfactants by on-line LC-NMR coupling is described. Different surfactant mixtures were separated by a mixed exclusion-adsorption method of liquid chromatography and simultaneously characterised by 1H-NMR spectroscopy. Information about the degree of oligomerisation of the ethylene oxide chain and the chemical structure of the endgroups can be obtained in a one-step experiment.
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    Synthesis and characterization of polyamides based on cubane-1,4-dicarboxylic acid (1997)
    Springer
    Polymer bulletin 38 (1997), S. 651-655 
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    Notes: Abstract. The direct polycondensations of cubane-1,4-dicarboxylic acid with 1,4-phenylenediamine (2 a), 4,4′-oxydianiline (2 b), 4,4′-sulfonyldianiline (2 c), and 9,9′-bis(4-aminophenyl)florene (2 d) were carried out in N-methyl-2-pyrrolidone/pyridine containing triphenylphosphite and lithium chloride at 110 °C for 9 h. Polyamide 3 a obtained from 2 a was scarcely soluble in organic solvent even during heating, and was soluble only in conc-H2SO4, whereas 3 c and 3 d derived from 2 c and 2 d, respectively, were readily soluble in N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethylsulfoxide. After treating polyamide 3 d with the rhodium complex catalyst in NMP, cubane units were quantitatively converted into cyclooctatetraenes.
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    Separation of block copolymers from parent homopolymers by means of liquid chromatography at the critical adsorption point (1997)
    Springer
    Polymer bulletin 38 (1997), S. 681-688 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The characterization of a block copolymer consisting of blocks of tetrahydrofuran, THF, and methyl methacrylate, MMA, was attempted with the aid of liquid chromatography, LC, at the critical adsorption point, CAP. The conditions applying to the CAP at 30 °C for the homopolymers are: PTHF: eluent composition: THF : acetonitrile = 50 : 50, w/w; column: Nucleosil C18. PMMA: eluent composition: THF : n-hexane = 81.8 : 18.2, w/w; column: bare silica gel. The presence of homo PTHF and of homo PMMA in the crude block copolymer was evidenced. Moreover, chromatography at the CAP for PMMA showed that the block copolymer contains multiblock (triblock) fractions. The formation of triblock copolymer is expected when the polymerization of MMA is terminated (partially) by combination. In conclusion, LC at the CAP is a powerful tool to characterize block copolymers regarding the presence of homopolymer and multiblock (triblock) fractions.
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    New thermoplastic polyolefin elastomers from the novel Multicatalysts Reactor Granule Technology: their relevant physical-mechanical properties after crosslinking (1997)
    Springer
    Polymer bulletin 38 (1997), S. 701-705 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. A new process for the sequential copolymerization of olefins has been devised (Multicatalysts Reactor Granule Technology); it allows the synthesis of thermoplastic polyolefin elastomers having polypropylene from Ti-based catalysts and ethylene-propylene rubbers from metallocenes. Such new materials have been cured with peroxides and the relevant mechanical properties measured in comparison with those of heterophasic copolymers synthesized with traditional catalysts. It resulted that the new materials present an improved balance between strength and elasticity, especially at high temperature.
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    Synthesis of graft copolymers by ring-opening polymerization of 2-nonyl- and 2-phenyl-2-oxazoline initiated by macroinitiators containing benzylchloride functions (1997)
    Springer
    Polymer bulletin 38 (1997), S. 657-664 
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    Notes: Abstract. Graft copolymers with poly(2-nonyl-2-oxazoline) and poly(2-phenyl-2-oxazoline) graft arms have been synthesized using the "grafting from" method. Slightly branched statistical copolymers of isobutene and (m,p)-chloromethylstyrene, synthesized cationically, as well as linear homo-poly((m,p)-chloromethylstyrene) have been used as macroinitiators for the ring-opening polymerization of the substituted oxazolines. The graft copolymerizations were carried out in bulk and in benzonitrile solutions with and without addition of potassium iodide. The influence of the reaction conditions on the rate of polymerization and the different reactivities of 2-nonyl-2-oxazoline and 2-phenyl-2-oxazoline were discussed.
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    The effect of stereoregularity on the thermal behavior of poly(methacrylic acid)s I. Thermal analysis studies (1997)
    Springer
    Polymer bulletin 39 (1997), S. 85-91 
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    Notes: Abstract. The thermal degradation of a series of poly(methacrylic acid)s (PMADs) with different tacticities has been investigated under inert atmosphere. All the samples showed two main degradation stages. The first decomposition process of isotactic PMAD consisted of the formation of anhydride groups, almost quantitatively, by dehydration. In the case of PMADs with lower isotactic content, the elimination of water between neighboring carboxylic groups is less favored and the anhydridization shifts at higher temperatures where other degradation reactions may take place at the same time. The temperatures of maximum volatilization rates at the second step of decomposition increased in the order isotactic 〉 atactic 〉 syndiotactic.
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    Rheometrical behavior and equilibrium swelling in NR/BR/CEL II composites (1997)
    Springer
    Polymer bulletin 39 (1997), S. 117-124 
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    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Natural rubber/butadiene rubber/cellulose II blends (NR/BR/CEL II) have been obtained by coprecipitation of the rubber latex-cellulose xanthate mixtures through acidulation. The elastomer ratio NR/BR has been varied from 100/0 to 25/75 and the cellulose content from 0 to 25 phr. The cure behavior of the compositions has been investigated by a Monsanto Oscillating Disk Rheometer. The results are a function of cellulose filler, NR, and BR contents. Some compositions were also analysed by equilibrium swelling in order to investigate polymer-filler interaction. The results show that composites with higher BR contents exhibit higher elastomer-filler attachment.
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    Polymerization by phase transfer catalysis 22. Synthesis of poly(amide-carbonate)s and poly(amide-thiocarbonate)s derived from diphenols with the amide group in the side chain (1997)
    Springer
    Polymer bulletin 39 (1997), S. 9-14 
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    Notes: Abstract. Poly(amide-carbonate)s and poly(amide-thiocarbonate)s derived from the diphenol-amides N-(2,6-dichloro-4-nitrophenyl)-2,2-bis(hydroxyphenyl)-propylamide (I), N-(2,6-dichloro-4-nitrophenyl)-3,3-bis(hydroxyphenyl)-butylamide (II), and N-(2,6-dichloro-4-nitrophenyl)-4,4-bis(hydroxyphenyl)-pentylamide (III), and phosgene or thiophosgene, have been synthesized under phase transfer conditions using several quaternary ammonium salts as phase transfer catalysts. Benzyltriethylammonium chloride (BTEAC) was effective in practically all cases due the hydrophilicity of this catalysts.
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    Interpolymer complex formation between form I helical and form II helical poly(l-proline) and poly(carboxylic acids) (1997)
    Springer
    Polymer bulletin 39 (1997), S. 45-52 
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    Notes: Abstract. Interpolymer complex formations between Form II helical poly(l-proline) [PLP(II)] and Form I helical poly(l-proline) [PLP(I)] and poly(carboxylic acids) such as polyacrylic acid (PAA), atatic polymethacrylic acid (at-PMAA), and syndiotatic polymethacrylic acid (st-PMAA) have been studied by FT-IR, X-ray diffraction, and light scattering measurements. It was found that the interpolymer complexes were formed via hydrogen bonding. The helical PLP(II) formed polymer complex more favorably with PAA and at-PMAA having a disordered structure than with st-PMAA having a ordered structure. In contrast, the helical PLP(I) formed polymer complex more favorably with st-PMAA than with PAA and at-PMAA. In addition, PLP(II) helix was destroyed on the complexation with PAA and at-PMAA, but the PLP(II) helix was perserved on the complexation with st-PMAA. However, the PLP(I) helix was all perserved on the complexation with poly(carboxylic acids). These findings could be explained in terms of molecular conformation of the complementary polymers associated with the complex formation.
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    Local motion of crosslinks for poly(methyl methacrylate) gels by the fluorescence depolarization method (1997)
    Springer
    Polymer bulletin 39 (1997), S. 109-116 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Poly(methyl methacrylate) (PMMA) gels labeled at crosslinks with anthracene were prepared. Anthracene fluorescence depolarization was monitored to probe the local motion of crosslinks for PMMA gels at different equilibrium swelling states. The relaxation times and the activation energies of local motion were measured for PMMA gels at the swollen states in various solvents through fluorescence anisotropy decays. The local motion of PMMA gel at crosslinks became faster with the increase of swelling ratio. When the swelling ratios were almost the same, the mobility of crosslinks was the same irrespective of the molecular weights between crosslinks. These results indicate that the local motion of crosslinks for PMMA gel is mainly governed by the segment density of network chains in the vicinity of crosslinks.
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    Influence of the structure and composition on surface tension of aqueous solution of graft copolymers of polyacrylamide backbone and polyalkyleneoxide branches (1997)
    Springer
    Polymer bulletin 39 (1997), S. 73-78 
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    Notes: Abstract. Polyacrylamide homopolymers and graft copolymers of poly(acrylamide-g-ethylene oxide) and poly(acrylamide-g-propylene oxide) were synthesized, characterized by SEC, FTIR and 13C-NMR and the behavior of their aqueous solutions was evaluated by surface tension measurements. By using the macromonomer technique, it is more difficult to incorporate poly(propylene oxide) branches than poly(ethylene oxide) branches. Graft copolymers of polyacrylamide and poly(propylene oxide) showed higher reduction of surface tension than poly(acrylamide-g-ethylene oxide) since they present a structure made up of hydrophilic and hydrophobic segments. Poly(acrylamide-g-propylene oxide) exhibits surfactant behavior, and the surface tension of its aqueous solution depends on the poly(propylene oxide) graft chain length and amount.
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    Transition temperature control of liquid crystalline poly(heptene sulphone)s (1997)
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    Polymer bulletin 39 (1997), S. 179-184 
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    Notes: Abstract. Liquid crystalline poly(heptene sulphone)s containing cholesteryl undecylenic ester and cholestanyl undecylenic ester were synthesized. The polymers displayed cholesteric mesophases during thermal transition. The clearing temperatures were from 114 to 172 °C depending on the molar ratio of mesogenic esters in the polymers.
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    Molecular dimensions of poly(ethylene isophthalate) and poly(ethylene naphthalene-2,6-dicarboxylate) (1997)
    Springer
    Polymer bulletin 39 (1997), S. 257-263 
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    Notes: Abstract. The rotational isomeric state (RIS) model was used to calculate the molecular dimensions of poly(ethylene isophthalate) (PEI) and poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) by introducing new description for aromatic segments and by adopting the statistical weight parameters of PET. The mean square dimension ratios ((〈r2〉0/M)∞) of PEN and PEI were 0.653 and 1.167, respectively, and the entanglement molecular weight (Me) of PEI and PEN were 1850 and 1810, respectively.
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    Effects of cyclization and pendant vinyl group reactivity on the swelling behavior of polyacrylamide gels (1997)
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    Polymer bulletin 39 (1997), S. 233-239 
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    Notes: Abstract. A series of polyacrylamide (PAAm) gels were prepared by free-radical crosslinking copolymerization of acrylamide and N,N′-methylenebis(acrylamide) (BAAm) in water at various crosslinker (BAAm) and chain transfer agent (isopropyl alcohol, IPA) concentrations. It was shown that only 5% of the crosslinker used in the feed forms effective crosslinks in the final hydrogels. At BAAm contents as high as 3 mole%, the equilibrium swelling ratio of the gels in water is independent of the crosslinker content in the feed. This is due to the prevailing multiple crosslinking reactions during the gel formation process. At a fixed crosslinker content, the onset of gelation is shifted towards higher conversions and reaction times as the amount of IPA increases. Addition of IPA in the monomer mixture also increases the equilibrium swelling ratio of PAAm gels. It was shown that the gel crosslinking density increases on rising IPA concentration in the feed due to the increasing rate of intermolecular crosslinking reactions.
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    Highly flexible heterophasic copolymers through the novel multicatalysts reactor granule technology (1997)
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    Polymer bulletin 39 (1997), S. 241-247 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. New heterophasic copolymers with high rubber content have been synthesized by combining heterogeneous Ti-based catalysts with metallocenes. The molecular, morphological and mechanical features of these materials were evaluated: it was pointed out that the new copolymers, having more than 60 Wt.% of rubber, perform as reinforced elastomers whereas traditional ones show a more plastomeric behaviour. This suggests that new polyolefin materials can augment rather than compete with the traditional ones.
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    Ethylene-propylene copolymers by a supported Ziegler-Natta catalyst based on TiCl4/MgCl2 (1997)
    Springer
    Polymer bulletin 39 (1997), S. 133-140 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Ethylene-propylene copolymers have been prepared by using Ziegler-Natta catalysts based on TiCl4, MgCl2, PCl3 and (n-Bu)3PO4. The catalysts TiCl4/MgCl2/PCl3 and TiCl4/MgCl2/(n-Bu)3PO4 were prepared by reacting TiCl4 with pretreated MgCl2. The support was prepared by ball milling of MgCl2 with varied amounts of PCl3 or (n-Bu)3PO4. The addition of PCl3 has remarkably increased the MgCl2 surface area in comparison with (n-Bu)3PO4. The effects of PCl3 and (n-Bu)3PO4 on ethylene homopolymerization, ethylene-propylene copolymerization and on copolymer properties were evaluated. The catalyst system containing PCl3 permitted to synthesize propylene-ethylene copolymers with up to 75% (w/w) of propylene and provided control of copolymer crystallinity. The reduction of the copolymer molecular weight distribution suggested that PCl3 acted as an internal donor, poisoning some active catalytic sites.
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    Grafting of side chain liquid crystal monomers onto polyethylene film (1997)
    Springer
    Polymer bulletin 39 (1997), S. 489-494 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. In order to obtain films of liquid crystalline polymers, a commercial polyethylene film was grafted with acryloyl chloride using γ-irradiation, and two tolane-containing alcohols were reacted with the chloride to obtain the corresponding acrylates. The morphology changes were studied by DSC, X-ray diffractometry and optical microscopy. The crystallinity of polyethylene films decreased by grafting, and mesophase with spherulites was observed over a wide temperature range.
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    Polymer-polymer interaction and modeling (1997)
    Springer
    Polymer bulletin 39 (1997), S. 519-526 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The nature of intermolecular interaction in PVC/EVA system was investigated. Bathochromic shifts in infrared region revealed that not only EVA carbonyl but the ester group participates on interaction with PVC chain. These shifts were proportional to acetate content in the copolymer and the composition of EVA in the blend. The PVC group that effectively participates on interaction was not elucidated by infrared spectrometry, but molecular modeling of low molecular weight analogues indicated that hydrogen bonding is the most probable kind of intermolecular interaction present in this system.
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    Application of an association model to the PVC/EVA system (1997)
    Springer
    Polymer bulletin 39 (1997), S. 527-534 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. A thermodynamic association model was applied to the PVC/EVA system. In this model the enthalpy component is related quantitatively to intermolecular interaction forces. Molecular modeling was applied to obtain the parameters related with interaction forces. The phase diagrams showed lower critical solution temperature (LCST) behavior and also biphasic regions in PVC rich compositions.
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    Synthesis, characterization, and properties of an efficient and selective adsorbent to mercury(II) (1997)
    Springer
    Polymer bulletin 39 (1997), S. 445-452 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The synthesis of a water-insoluble adsorbent resin was carried out by radical polymerization of [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride by using ammonium peroxydisulfate as initiator and N,N′-methylene-bis-acrylamide (MBA) as crosslinking reagent. The adsorbent was characterized by elemental analyses, and FT-IR spectroscopy. The thermal stability was studied in the presence of Hg(II). The ability to bind Hg(II), Cd(II), Zn(II), Pb(II), Cu(II), Cr(III), and U(VI) as well as the maximum adsorption capacity, and elution of the Hg(II) from the loaded resin was studied. At pH 2 the adsorbent retained 95% of Hg(II) from an aqueous solution containing 1 g/L in Hg(II). The retention of other metal ions was lower than 15%. Sorption selectivity from the binary mixtures Hg(II)-Cd(II), Hg(II)-Zn(II), Hg(II)-Pb(II), and Hg(II)-Cr(III) was studied at the optimum sorption pH value.
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    Dendrite polymers from vinyl ether (1997)
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    Polymer bulletin 39 (1997), S. 399-406 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. 1-[(2-Vinyloxy)ethoxy]ethyl acetate (1) was prepared by the addition reaction between ethylene glycol divinyl ether and acetic acid. 1 contains both a cationically polymerizable C=C double bond and a dormant initiating moiety for cationic polymerization. It can, therefore, undergo self condensing cationic polymerization in the presence of a Lewis acid activator, such as zinc chloride. Using this procedure, a novel dendritic polymer consisting of vinyl ether was prepared and its hyperbranched molecular structure confirmed by FT-IR and 1H NMR spectra.
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    On a novel molecular microstructure based approach to the extrinsic space charges releasing in polypropylene (PP) (1997)
    Springer
    Polymer bulletin 39 (1997), S. 639-646 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The release of the extrinsic charges produced when applying an electric stress has been studied for four polypropylene samples of distinct well controlled molecular microstructure by Thermal Stimulated Discharge Current (TSDC), with the aim of stating the correlation between the ρ relaxation (intensity and temperature) and the tacticity induced polymer microstructure, and of, demonstrating that the traps of space charges are not chain defects as usually proposed but that they relate to some normal local chain configurations. The results are discussed in the light of the space charge distributions as measured in earlier recent work.
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    Regioselective introduction of β-galactoside branches into chitosan and chitin (1997)
    Springer
    Polymer bulletin 39 (1997), S. 543-549 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. β-d-Galactoside branches have been introduced into chitosan and chitin regioselectively through a series of controlled modification reactions based on N-phthaloyl-chitosan. The glycosylation reaction between a chitosan derivative having a reactive group only at C-6 and an orthoester of d-galactose proceeded efficiently to give a protected product with a degree of substitution up to about 0.5. Deprotection gave a branched chitosan, and the subsequent N-acetylation afforded a branched chitin. Unlike chitosan and chitin, the resulting nonnatural branched polysaccharides were characterized by high affinity for solvents and readily soluble in neutral water. Furthermore, branched chitin was easily degraded by lysozyme.
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    Effective catalysts for polymerization of cyclohexene oxide: Preparation of novel Martin-type pentacoordinate silicates (1997)
    Springer
    Polymer bulletin 39 (1997), S. 573-579 
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    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract. The novel dialkylanilinium salts of pentacoordinate Martin-type silicates were prepared. They were found to be air stable catalysts for polymerization of cyclohexene oxide. The preparation of those silicates bearing a bulky substituent such as mesityl group was not successful.
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    Molecular packing of poly(azomethine)s having flexible (n-alkyloxy)methyl side chains in films (1997)
    Springer
    Polymer bulletin 39 (1997), S. 701-705 
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    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The molecular packing of poly(azomethine)s having (n-alkyloxy)methyl side chains in films was studied by wide-angle X-ray scattering. Solution-cast films on silicon wafer and melt-sheared films show the same type of molecular packing, i.e. the main chain layers are aligned parallel to the film surface but the main chains are macroscopically isotropic in the film surface plane. In the melt-sheared films, the shear does not orient the main chains but the main chain layers, which can be easily understood by their geometric shapes.
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    Characteristics of permeation and separation of dimethyl acrylamidemethyl methacrylate random and graft copolymer membranes for a benzene/cyclohexane mixture (1997)
    Springer
    Polymer bulletin 39 (1997), S. 733-740 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. When a benzene/cyclohexane mixture was permeated through poly(dimethyl acrylamide-random-methyl methacrylate) (DMAA-r-MMA) and poly(dimethyl acrylamide)-graft-poly(methyl methacrylate) (DMAA-g-MMA) membranes by pervaporation, the benzene-permselectivity of the DMAA-r-MMA membrane changed from the diffusivity selectivity to the solubility selectivity with increasing DMAA content but DMAA-g-MMA membranes with a high DMAA content had the higher apparent diffusivity selectivity than the apparent solubility selectivity. Furthermore, the apparent solubility selectivity for a benzene/cyclohexane mixture between the DMAA-r-MMA membrane and the DMAA-g-MMA membrane with a high DMAA content was remarkably different. These results were attributed to the difference of structure between the copolymers.
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    Oriented overgrowth of vapour deposited tin on highly oriented PTFE substrates (1997)
    Springer
    Polymer bulletin 39 (1997), S. 761-765 
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    ISSN: 1436-2449
    Keywords: metal/polymer interface – friction transfer – ultra-thin films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The vapour deposition of tin on highly uniaxially oriented PTFE causes an oriented overgrowth of tin islands. The origin of this orientation is not clear. Classic epitaxy as well as graphoepitaxy seems to be an explanation for the occurring orientation. The appearance of this orientation was observed in a temperature range from −80 °C to 90 °C. An orientation by crystallization from the melt could not be achieved so far. In this short communication, a metal/polymer system is introduced which offers new possibilities to investigate the origin of oriented overgrowth.
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    Polymerization of methyl and phenyl oxazoline initiated with carboxylic acid chlorides (1997)
    Springer
    Polymer bulletin 38 (1997), S. 7-13 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Methyl and phenyl oxazoline were polymerized using carboxylic acid chlorides as initiators. The first step of the reaction was shown to consist in a fast reaction of the carboxylic acid chloride with the oxazoline. Resulting product, which was isolated and identified, act as the proper initiator of the polymerization of the oxazoline, which proceeds via covalent or, when chloride counter ion is replaced with iodide or triflate, ionic active species. Apparent rate constants of the chain growth were determined. When methacryloyl chloride is used as initiator macromonomers are obtained, which were copolymerized with styrene. Macromolecular carboxylic acid chlorides initiate the polymerization of oxazolines, yielding graft polymers.
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    Photodegradation of chain halogenated polystyrene: Poly(c-chloro and c-bromostyrene)s (1997)
    Springer
    Polymer bulletin 38 (1997), S. 191-196 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The photodegradation of films of poly chain-chlorostyrene (PCCS) and poly chain-bromostyrene (PCBS) achieved by exposure to 254-nm radiation under dynamic vacuum was studied. The minor gaseous products obtained were hydrogen halides and monomer. The polymers were investigated by ir, gel permeation chromatography, and microanalysis. Both polymers undergo main chain scission. The ir spectra of the degraded polymers indicate the presence of unsaturated species. An initial α-carbon-halogen bond fission is required to account for the present reaction products. Possible mechanism of the various photoreactions are discussed.
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    Compatibilization of low-density polyethylene/polystyrene blends by segmented EB(PS-block-EB)n block copolymers (1997)
    Springer
    Polymer bulletin 38 (1997), S. 203-210 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Hydrogenated segmented poly[butadiene-block-(styrene-block-butadiene)n] block copolymers, which were developed by use of a polymeric iniferter technique, were tested on their compatibilizing effectiveness for (10/90) LDPE/PS blends. They were found to be effective compatibilizers for this mixture, already giving a pronounced improvement in both tensile strength and strain of the blend at block copolymer concentrations of one percent. A concentration of five weight percent of segmented block copolymer provided a tenfold improvement in blend toughness. The effectiveness of the segmented block copolymers was found be dependent on the block copolymer composition. Block copolymer compositions of close to 50 : 50 EB : PS gave the best results.
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    Dynamic mechanical behaviour of random copolymers of a LC-methacrylate and octyl methacrylate (1997)
    Springer
    Polymer bulletin 38 (1997), S. 219-226 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The dynamic mechanical behaviour of random copolymers of LC monomer-1-(hexyloxycarbonyl)ethyl 4-[4-(methacryloyloxy)benzoyloxy]benzoate (HB) and octyl methacrylate (OMA) was studied in the main transition and flow regions. Even though the aliphatic end groups of the side chain of HB and OMA are roughly the same, the T g temperature of poly(HB) is ∼ 80 K higher than that of poly(OMA); this fact is due to the presence of the stiff phenyl benzoate mesogenic group in the side chain of HB. With increasing content of OMA in the copolymer the superimposed curves of the storage G′ p and loss G′′ p moduli at a constant temperature shift towards shorter frequencies. It has been shown that this shift is mainly due to an increase of the free volume in the copolymers with increasing content of OMA. While HB monomer shows liquid crystalline (LC) properties, its polymer (poly(HB)) and random copolymers with OMA show only isotropic thermal behaviour because no flexible spacer is present in the side chain of HB which would decouple the main chain and mesogenic group motions. This means that neither the homopolymer of HB, nor its copolymers with a flexible comonomer retain the LC properties of the starting LC monomer, HB.
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    A new approach to anisotropic conductive networks A liquid-crystalline side-chain polymer containing a thienyl moiety at the extremity of its side chain (1997)
    Springer
    Polymer bulletin 38 (1997), S. 551-554 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. A liquid-crystalline bifunctional monomer with two different reactive moieties was prepared by esterification of 4-(6-(acryloyloxy)hexyloxy)benzoic acid and 4-[11-(3-thienyl)undecyloxy]-4′-hydroxybiphenyl. A mesogenic side-chain polyacrylate containing a thienyl moiety at the extremity of its side chain was obtained by radical polymerization of the monomer. The subsequent reaction of the thienyl moiety with FeCl3 leads to the formation of an anisotropic network with a poly(thiophene) unit.
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    Asymmetric polymerization of N-triphenylmethylmaleimide with chiral anionic initiators (1997)
    Springer
    Polymer bulletin 38 (1997), S. 509-514 
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    Notes: Abstract. Asymmetric polymerization of N-triphenylmethylmaleimide (TrMI) is performed with chiral anionic initiators in tetrahydrofuran and toluene at − 78 and 0 °C to obtain optically active polymer. It is found that the (S)-(+)-1-(2-pyrrolidinylmethyl) pyrrolidinelithium [Li-(+)-PMP] and lithium (−)-menthoxide are effective for the asymmetric polymerization of N-triphenylmethylmaleimide in THF. The polymers obtained are characterized by circular dichroism (CD). It is inferred that the propagation reaction of polymerization of TrMI with Li-(+)-PMP is dominated by ion pair mechanism and meanwhile free ion mechanism cannot be ignored based on GPC analysis.
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    Synthesis and characterization of some polyazomethine conducting polymers and oligomers (1997)
    Springer
    Polymer bulletin 39 (1997), S. 1-7 
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    Keywords: Key words: polyazomethines – oligomers – conducting polymers – synthesis – characterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Polyazomethine polymers were prepared from the polycondensation of terephthaldehyde with different diamines, namely, benzidine, 2,3-diaminopyridine, 1,4-diaminoanthraquinone and 3,5-diamino-1,2,4-triazole. The electrical conductivities of the polymers were studied with doping with H2SO4 and 5% I2 together with the undoped polymers. The crystallinity and morphology of the polymers were studied using XRD and scanning electron microscopy. A comparative study of the electrical conductivities of oligomers of polyazomethines and those of their corresponding polymers was performed.
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    Syntheses and radical ring-opening polymerizations of 1,1-bis(hydroxymethyl)-2-vinylcyclopropane and 1,1-bis(methoxymethyl)-2-vinylcyclopropane (1997)
    Springer
    Polymer bulletin 39 (1997), S. 141-148 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Syntheses and radical ring-opening polymerization of 1,1-bis(hydroxymethyl)-2-vinylcyclopropane (1 a) and 1,1-bis(methoxymethyl)-2-vinylcyclopropane (1 b) were examined. Novel polymers bearing hydroxyl and methyl ether moieties in the side chains as well as olefinic moieties in the main chain were obtained. The main structure of the polymers, obtained by radical polymerization, originated from the cleavage of the cyclopropane ring near the hydroxymethyl or methoxymethyl groups. The difference in the two-center energies and bond orders of the C−C bonds of the cyclopropane ring well explained the selectivity in the direction of the cleavage. The number-average molecular weights (Mˇ n) of poly(1 a) and poly(1 b) were 94 200 and 11 200 in the polymerization in bulk at 60 °C, respectively. The intermolecular hydrogen bonding of 1 a might increase the radical polymerizability. The oxygen permeability of poly(1a) was 6.19 mL ⋅ 20 mm ⋅ m−2 ⋅ day−1 ⋅ atm−1 at 35 °C, demonstrating that poly(1 a) could be a good oxygen barrier material.
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    Radical polymerization of (trimethylsilylethynyl)styrene and thermal properties of polystyrene with ethynyl group (1997)
    Springer
    Polymer bulletin 39 (1997), S. 173-178 
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    Notes: Abstract. The radical polymerizations of 2-, 3-, and 4-(trimethylsilylethynyl)styrenes (1 a – c) and copolymerizations of 1 a – c (M1) with styrene (M2) have been studied. Copolymerization parameters were determined as r1 = 1.22 and r2 = 0.54 for 1 a, 1 = 1.10 and r2 = 0.90 for 1 b, and r1 = 1.42 and r2 = 0.38 for 1 c. The deprotection of the trimethylsilyl groups in poly[(trimethylsilylethynyl)styrene] (2 a – c) and poly[(trimethylsilylethynyl)styrene-co-styrene] (4 a – c) using (C4H9)4NF smoothly proceeded to yield poly(ethynylstyrene) (3 a – c) and poly(ethynylstyrene-co-styrene) (5 a – c), respectively, which underwent curing reactions at elevated temperature to form crosslinking polystyrenes.
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    Surface activity of water soluble amphiphilic chitin derivatives (1997)
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    Polymer bulletin 39 (1997), S. 209-215 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Chitin was derivatized to extend its applications in the field of water soluble systems. It was first carboxymethylated and then alkylated. Two technics were used for that purpose: ionic surfactants playing the role of counterions form an electrostatic complex, and covalent derivatization. The difference between covalent alkylation and dynamic association (SPEC) is discussed in relation with the length of the alkyl chain and the density of alkylation.
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    Study of siloxane-modified epoxy resin using thermally stimulated current(II) (1997)
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    Polymer bulletin 39 (1997), S. 193-199 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Thermally stimulated current (TSC) and relaxation map analysis (RMA) was used to characterize the low temperature relaxation of epoxy resin modified with siloxane oligomers. In aminopropyl-terminated siloxane oligomer (ATSO) the β-relaxation of epoxy resin and the glass transition temperature of siloxane oligomer were folded regardless of the concentration of diphenyl. The β-relaxation of epoxy resin and the glass transition temperature of oxiranylmethoxy-terminated siloxane oligomer (OTSO) were folded and shifted to higher temperature as the concentration of diphenyl in siloxane oligomer increased. In the systems containing of diphenyl in siloxane oligomer a new relaxation peak due to the space charge was observed in the range of − 80 °C to − 50 °C and − 30 °C to 5 °C. As the concentration of diphenyl increased the compensation temperature (Tc) and the degree-of-disorder (DOD) were increased while the compensation time, τ c was decreased.
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    URL: http://dx.doi.org/10.1007/s002890050138
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    Microwave assisted polymerisation of phenylacetylenes (1997)
    Springer
    Polymer bulletin 39 (1997), S. 333-337 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary. Methathesis Polymerisation of phenylacetylenes using in situ generated (arene)M(CO)3 complexes under unconventional microwave energy condition was achieved successfully. The reaction time was reduced to 1 hour in contrast to refluxing conditions of 24 hours.
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    URL: http://dx.doi.org/10.1007/s002890050156
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    Transition metal complex induced morphology change in an ABC-triblock copolymer (1997)
    Springer
    Polymer bulletin 39 (1997), S. 361-368 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary. The short 1,2-polybutadiene center block of the ternary polystyrene-block-polybutadiene-block-poly(methyl methacrylate) S45B6M49 225-triblock copolymer (subscripts indicating the weight fractions and the superscript indicating the total molecular weight in kg/mol) has been selectively modified by complexation with metal complexes of two different transition metals, namely Pd and Fe. These modifications cause significant variations in the microphase morphology. The original ls-morphology (spheres at lamellar interphase) belonging to the lamellar class changes via a cocontinuous morphology in the case of the Pd-complex to a morphology belonging to the cylindrical class for the Fe-complex.
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    URL: http://dx.doi.org/10.1007/s002890050160
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    Kinetics of formation of polyurethane/polymethylmethacrylate grafted semi-interpenetrating polymer networks based on the functional prepolymers (1997)
    Springer
    Polymer bulletin 39 (1997), S. 339-346 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary. The kinetics of formation of the polyurethane network by crosslinking the polyurethane prepolymer in polyurethane/polymethacrylate grafted semi-interpenetrating networks (semi-IPN) was monitored by Fourier transform infrared spectroscopy, and the kinetic parameters were thus determined. It was found that carboxylic groups in the hard segments of the Pu component substantially decrease the reaction rate and increase the activation energy. Tertiary amine groups in the PM component catalyse the crosslinking reaction. The PM component acts as a diluent in the mixture of PU and PM reducing the reaction rate and increasing the activation energy of the corsslinking reaction. At temperatures below the Tg of the PM component, the reaction of formation of IPN becomes diffusion controlled.
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    Synthesis of polystyrene/silica gel polymer hybrids by in-situ polymerization method (1997)
    Springer
    Polymer bulletin 39 (1997), S. 303-310 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary. Homogeneous polystyrene and silica gel polymer hybrids were prepared by in-situ radical polymerization method. Styrene monomer was introduced into a sol-gel reaction mixture of tetramethoxysilane (TMOS) and the polymerization was initiated by Azobisisobutyronitrile (AIBN), while sol-gel reaction of TMOS proceeded to form a silica gel. The homogeneity of the hybrids was found to be dependent on the amount of the acid catalyst. The homogeneity was confirmed quantitatively by measuring porosity of charred hybrids with nitrogen porosimetry method. It was found that polystyrene was dispersed at a nano-meter level in the silica gel matrix.
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    Synthesis of novel organoboron polymers by haloboration polymerization of bisallene compounds and their reactions (1997)
    Springer
    Polymer bulletin 39 (1997), S. 295-302 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary. Novel organoboron polymers were prepared by haloboration polymerization of bisallene compounds. The polymers obtained have allylborane halide units in their main chain and can be expected as a novel type of reactive polymers. For example, the polymer prepared by haloboration polymerization between tribromoborane (1) and 1,2,10,11-dodecatetraene (2 b) was subjected to chain transformation reaction (dichloromethyl methyl ether rearrangement) to give the corresponding polyalcohol or polyketone. Haloboration-phenylboration polymerization of aliphatic bisallenes by using diphenylbromoborane also gave the corresponding polymers.
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    Anionic polymerization of vinylsilanes VII. Effects of N,N,N',N'-tetramethylethylenediamine on the polymerization of tetravinylsilane (1997)
    Springer
    Polymer bulletin 39 (1997), S. 287-293 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary. The anionic polymerization of tetravinylsilane (TeVS) was carried out in the presence and absence of N,N,N',N'-tetramethylethylenediamine (TMEDA). Without TMEDA, the polymerization proceeded extremely slowly and the polymer yield was still low even after an extended polymerization time. When TMEDA was added to the system, the polymerization was remarkably accelerated and gelation was suppressed. Such polymerization behavior of TeVS is closely similar to that of methyltrivinylsilane under similar conditions. The effects of TMEDA are explained by its coordination to the propagating end that increases the selectivity in the reaction of the propagating end with vinyl groups.
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    Investigation of adhesive performances by scanning force microscopy (1997)
    Springer
    Polymer bulletin 39 (1997), S. 613-620 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. In this work an original investigation of the polymer adhesive properties by scanning force microscopy (SFM) is proposed. Polyethylene terephthalate (PET)/ethylene vinylacetate copolymers (EVA) assemblies have been separated using a peel test. SFM (tapping mode) is used to study the adhesive surface (EVA) after the mechanical separation. The topographic analysis allows to determine the average roughness due to the polymer surface deformation. A tentative correlation between the surface deformation and the adherence force is proposed. The result show that the polymer which possess the higher adhesive strength presents the greater surface deformation, measured on the SFM image. A relatively good correlation between the evolution of the adherence force and the variation of the surface topography analysed by SFM is highlighted in this original work.
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    Conductive polyaniline/poly(vinylphosphonic acid) blends (1997)
    Springer
    Polymer bulletin 39 (1997), S. 627-632 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. In-situ polymerization of aniline in poly(vinylphosphonic acid) (PVPA) resulted in conductive polyaniline/PVPA blends with conductivities in the order of 10−2 S/cm. The blends were characterized by FTIR and UV-vis spectroscopy. Thermogravimetric analysis showed that the blends have good thermal stability.
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    Poly(allylammonium acrylate) as a drug-releasing matrix I. Release of drugs mixed and sintered with the polyelectrolyte complex (1997)
    Springer
    Polymer bulletin 39 (1997), S. 707-714 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. A poly(allylammonium acrylate) complex was tested for drug release in aqueous solution. Sintered tablets of the polyelectrolyte complex, mixed respectively with human serum albumin, vitamin B12, 5-fluorouracil and tetracycline, were made and dipped into Dulbecco's PBS (pH 7.3). The release kinetics, followed spectrophotometrically, is poorly reproducible and very different for the different drugs. An explanation of such behaviours is proposed, based on the chemical structures of the drugs and of the polyelectrolyte complex, as well as on two concurrent processes: the drug extraction and the saturation by the buffer of the poorly uniform drug-complex mechanical mixtures.
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    Synthesis of fullerene-containing poly(alkyl methacrylate)s with narrow polydispersities (1997)
    Springer
    Polymer bulletin 39 (1997), S. 661-667 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Copolymers of allyl methacrylate with methyl methacrylate or n-butyl methacrylate were synthesized by group transfer polymerization. The pendant allyl groups of the copolymers were then hydrobrominated, followed by reaction with sodium azide. Fullerene was incorporated via an addition reaction of fullerene with azide group. The resulting fullerene-containing poly(alkyl methacrylate)s have fairly narrow polydispersities.
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    Modeling spurt and stress oscillations in flows of molten polymers (1997)
    Springer
    Rheologica acta 36 (1997), S. 110-127 
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    ISSN: 1435-1528
    Keywords: Key words Spurt ; oscillations ; wall slip ; capillary flows ; stick-slip ; critical shear stress ; loss of fluidity ; hardening ; parameter ; extrudate distortion ; melt fracture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The paper presents an approach for modeling polymer flows with non-slip, slip and changing non-slip – slip boundary conditions at the wall. The model consists of a viscoelastic constitutive equation for polymer flows in the bulk, prediction of the transition from non-slip to sliding boundary conditions, a wall slip model, and a model for the compressibility effects in capillary polymer flows. The bulk viscoelastic constitutive equation contains a hardening parameter which is solely determined by the polymer molecular characteristics. It delimits the conditions for the onset of solid, rubber-like behavior. The non-monotone wall slip model introduced for polymer melts, modifies a slip model derived from a simple stochastic model of interface molecular dynamics for cross-linked elastomers. The predictions for the onset of spurt, as well as the numerical simulations of hysteresis, spurt, and stress oscillations are demonstrated. They are also compared with available data for a high molecular weight, narrow distributed polyisoprene. By using this model beyond the critical conditions, many of the qualitative features of the spurt and oscillations observed in capillary and Couette flows of molten polymers, are described.
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    Shear rheology of polymer solutions near the critical condition for elastic instability (1997)
    Springer
    Rheologica acta 36 (1997), S. 97-109 
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    ISSN: 1435-1528
    Keywords: Key words Polymer migration ; anomalous rheology ; Boger fluid ; normal stress ; elastic instability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The use of constant viscosity, highly elastic polymer solutions, so called Boger fluids, has been remarkably successful in elucidating the behavior of polymeric materials under flowing conditions. However, the behavior of these fluids is still complicated by many different physical processes occurring within a narrow window of observation time and applied shear rate. In this study, we investigate the long-time shear behavior of an ideal Boger fluid: a well characterized, athermal, dilute, binary solution of high molecular weight polystyrene in oligomeric polystyrene. Rheological measurements show that under an applied steady shear flow, this family of polymer solutions undergoes a transient decay of normal stresses on a timescale much longer than the polymer molecule‘s relaxation time. Rheological and flow visualization results demonstrate that the observed phenomenon is not caused by polymer degradation, phase separation, viscous heating, or secondary flows from elastic instabilities. Although the timescale is much shorter than that associated with polymer migration in the same solutions (MacDonald and Muller, 1996), the appearance of this phenomenon only at the rates where migration has been observed suggests that it may be a prerequisite for observing migration. In addition, we note that through sufficient pre-shearing of the sample, the normal stress decrease suppresses the elastic instability. These results show that there is considerable uncertainty in choosing the appropriate measure of the fluid relaxation time for consistently modeling the critical condition for the elastic instability, the decay of normal stresses, and the migration of polymer species.
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    Isothermal elongational behavior of liquid- crystalline polymers and LCPs based blends (1997)
    Springer
    Rheologica acta 36 (1997), S. 152-159 
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    ISSN: 1435-1528
    Keywords: Key words Elongational flow ; liquid crystalline polymer ; polymer blends
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The rheological behavior of two flexible thermoplastics, Nylon-6 (Ny) and bisphenol-A polysulfone (PSu), and two wholly aromatic liquid crystalline polymers, Vectra-A900 (VA) and Vectra-B950 (VB), as well as that of Ny/VB and PSu/VA blends with 10% LCP, has been investigated by the use of capillary viscometers equipped with cylindrical dies having different length-to-diameter ratios. The elongational viscosity of all materials was calculated, from the results of isothermal measurements carried out at 290°C, by means of the Cogswell‘s analysis, based on the estimation of the pressure drop due to the converging flow at the die inlet. The behavior in elongational flow was compared with the rheological behavior in shear flow conditions. It was found that the elongational viscosities of VA and VB are very large and account for a fairly marked pressure drop at the die entrance, due to the orientation of the LCP domains taking place in the converging flow zone. For these materials, the ratio of the elongational viscosity to the Newtonian shear viscosity is up to two orders of magnitude higher than the value expected on the basis of the Trouton rule. For the flexible resins, the Trouton ratio is 3 and ca. 3–10, are common values for high molar mass linear polymers. The addition of 10% LCP into the flexible resins strongly increases their elongational viscosity and makes the blends resemble neat LCPs in their extensional flow behavior. In shear flow, on the contrary, the addition of LCP was shown to induce a marked reduction of the melt viscosity, even when, as for the Ny/VB blend, the LCP is more viscous than the matrix.
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    The effect of parallel combined steady and oscillatory shear flows on blood and polymer solutions (1997)
    Springer
    Rheologica acta 36 (1997), S. 160-172 
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    ISSN: 1435-1528
    Keywords: Key words Viscoelasticity ; blood ; aggregation ; model fluid ; polyacrylamide ; xanthan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Human blood at physiological volume concentration exhibits non-Newtonian and thixotropic properties. The blood flow in the microcirculation is pulsatile, initiated from the heart pulse and can be considered as superposition of two partial flows: a) a steady shear, and b) an oscillatory shear. Until now steady and viscoelastic behavior were separately investigated. Here we present the response to the combination of steady and oscillatory shear for human blood, a high molecular weight aqueous polymer solution (polyacrylamide AP 273E) and an aqueous xanthan gum solution. The polyacrylamide and xanthan solutions are fluids that model the rheological properties of human blood. In general, parameters describing blood viscoelasticity became less pronounced as superimposed steady shear increased, especially at low shear region and by elasticity, associated with reduction in RBC aggregation. The response of polymer solutions to superposition shows qualitative similarities with blood by elasticity, but their quantitative response differed from that of blood. By viscosity another behavior was observed. The superposition effect on viscous component was described by a modified Carreau equation and for the elastic component by an exponential equation.
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    Generalized Maxwell model for the viscoelastic behavior of a soda-lime-silica glass under low frequency shear loading (1997)
    Springer
    Rheologica acta 36 (1997), S. 173-186 
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    ISSN: 1435-1528
    Keywords: Key words Viscoelasticity ; dynamic experiments ; viscoelastic constants ; generalized Maxwell model ; soda-lime-silica glass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The linear viscoelastic behavior of a soda-lime-silica glass under low frequency shear loading is investigated in the glass transition range. Using the time-temperature superposition technique, the master curves of the shear dynamic relaxation moduli are obtained at a reference temperature of 566°C. A method to determine the viscoelastic constants from dynamic relaxation moduli is proposed. However, some viscoelastic constants cannot be directly measured from the experimental curves and others cannot be precisely obtained due to non-linearity effects at very low frequencies. The generalized Maxwell model is investigated from the experimental dynamic moduli without fixing the viscoelastic constants. A set of parameters is shown to be in good agreement with the experimental dynamic relaxation moduli, but does not give the correct values of the viscoelastic constants of the investigated glass. The soda-lime-silica glass exhibits a non-linear viscoelastic behavior at very low stress level which is usually observed for organic glasses. This non-linear behavior is questioned.
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    Non-linear flow properties of viscoelastic surfactant solutions (1997)
    Springer
    Rheologica acta 36 (1997), S. 13-27 
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    ISSN: 1435-1528
    Keywords: Viscoelastic surfactant solution ; non-linear flow ; Giesekus model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract This paper gives a quantitative description of the viscoelastic properties of aqueous solutions of entangled rod-shaped micelles. The experimental data are compared with the theoretical predictions of a special constitutive equation which is based on the concept of deformation-dependent tensorial mobility. In the regime of small deformations, shear stresses or shear rates, the dynamic features of the viscoelastic solutions are characterized by the equations of a simple Maxwell material. These phenomena are linked to the average lifetime of the micellar aggregates and the rheological properties are controlled by kinetic processes. At these conditions one observes simple scaling laws and linear relations between all theological quantities. At elevated values of shear stresses or deformations, however, this simple model fails and non-linear properties as normal stresses, stress overshoots or shear-thinning properties occur. All these phenomena can be described by a constitutive equation which was first proposed by H. Giesekus. The experimental results are in fairly good agreement with the theoretical predictions, and this model holds for a certain, well defined value of the mobility factor α. This parameter describes the anisotropic character of the particle motion. In transient and steady-state flow experiments we always observed α = 0.5. Especially at these conditions, the empirically observed Cox-Merz rule, the Yamamoto relation and both Gleißle mirror relations are automatically derived from the Giesekus model. The phenomena discussed in this paper are of general importance, and can be equally observed in different materials, such as polymers or proteins. The viscoelastic surfactant solutions can, therefore, be used as simple model systems for studies of fundamental principles of flow.
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    Laser Doppler measurements of flow in a cone-and-plate rheometer and the effect of cone misalignment (1997)
    Springer
    Rheologica acta 36 (1997), S. 28-37 
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    ISSN: 1435-1528
    Keywords: Cone-and-plate rheometer ; laser Doppler velocimetry ; misaligned cone-and-plate geometry ; secondary flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Laser Doppler velocimetry (LDV) is used to measure the flow profile of a Newtonian fluid in a cone-and-plate rheometer. The primary and secondary flow patterns are measured in the ideal geometry. The results confirm prior predictions of flow patterns. Flow profiles are also measured in the misaligned geometry in which the cone axis of rotation is tilted slightly off the perpendicular with the plate surface. Numerical predictions of these flow patterns (Dudgeon and Wedgewood, 1994) are also confirmed.
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    Experimental validation of steady shear and dynamic viscosity relation for yield stress fluids (1997)
    Springer
    Rheologica acta 36 (1997), S. 49-55 
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    ISSN: 1435-1528
    Keywords: Rheometry ; yield stress ; shear
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A common problem when studying yield stress fluids under steady shear in rotating rheometry is that of sample fracture. It is therefore preferable to work with oscillating shear, where fracture is limited. Doraiswamy et al. (1991) proposed a model for yield stress fluids that predicts the relation: η*(γ m ω) = η(y) between the viscosity in steady shear and the complex viscosity in dynamic shear. The present study validates this relation experimentally with both controlled stress and controlled strain, and demonstrates its limitations. Three yield stress fluids were used: a lubricating grease with lithium based soap, a thixotropic dispersion of colloidal silica in a polymer solution and a non-thixotropic aqueous gel.
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    Influence of the flow history on stress growth and structure changes in the thermotropic liquid crystalline polymer Vectra B950 (1997)
    Springer
    Rheologica acta 36 (1997), S. 82-95 
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    ISSN: 1435-1528
    Keywords: Vectra B950 ; thermotropic LCP ; rheology ; structure ; orientation ; transients ; dynamic moduli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The structure changes in the start-up flow of the thermotropic liquid crystalline polymer Vectra 8950 are probed by performing transient experiments after various flow histories. The shear and normal stress growth curves of a squeezed sample and of a randomly oriented sample show a pronounced overshoot at low strains, whereas the stress growth curve of a sample pre-sheared until steady state shows a gradual increase. This first peak is associated with the re-orientation of the director into the shearing plane. All stress transients show a second broad maximum at large strains that results from the generation of a steady defect network. The effect of varying the relaxation period after pre-shearing is reflected in the appearance of two peaks in the subsequent stress growth curves. One of these peaks shifts linearly with re laxation period and the other is more or less fixed in position. The orientation of the molecules during steady shear flow is on average in the flow direction. Intermediate orientation levels may exist in the transient depending on the amount of strain. The material is able to maintain the flow-induced orientation distribution for a long time after cessation of flow. This is reflected in a similar fashion in the initial magnitudes of the stresses and the dynamic moduli after various preshear strains. Moreover, the dynamic moduli decrease with time after cessation of steady shear flow, indicating that the orientation increases during relaxation.
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    Oscillatory and simple shear flows of a flour-water dough: a constitutive model (1997)
    Springer
    Rheologica acta 36 (1997), S. 38-48 
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    ISSN: 1435-1528
    Keywords: Key words Dynamic data of dough ; viscometric data of dough ; rheology of dough ; constitutive modelling of dough
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract We reported some dynamic and viscometric data on an Australia strong flour-water dough. In oscillatory shear flow experiments, we found the linear viscoelastic strain limit is extremely low, of O(10–3), consistent with other published data on doughs. The relaxation spectrum derived from the dynamic data is broad, indicating the “blend” nature of dough. In the start-up of a simple shear flow, we found the shear stress increases nonlinearly with time to a peak value and then decreases rapidly, with no steady-state response. The concept of steady-state viscosity is not very meaningful here, unless the strain at which the measurements are taken is also specified. The stress peaks are strain-rate dependent; but they occur at a strain of O(10), for the strong flour/water dough used, over four decades of strain rates. The experimental data were used to construct a phenomenological model for dough, consisting of an hyperelastic term (representing the elastic gluten network of permanent cross-linked long chain polymers), and a viscoelastic contribution (representing the suspension of starch globules and other long-chain components in dough that are not parts of the permanent cross-linked gluten network). The model predictions compared favourably with experimental data in oscillatory and shear flows.
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    Stability of the T ∞FT 〈 T ∞α relation between Vogel temperatures of flow and glass transition against determination variants (1997)
    Springer
    Rheologica acta 36 (1997), S. 187-196 
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    ISSN: 1435-1528
    Keywords: Glass transition ; flow transition ; polystyrene ; poly(vinyl acetate) ; Vogel temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Dynamic shear measurements in the frequency range from 10−4 to 500 rad/s at the flow and main transition of a polydisperse poly(vinyl acetate) and a monodisperse polystyrene sample are presented. For both samples the Vogel temperature of the flow transition T ∞FT is smaller than the Vogel temperature of the main transition T ∞α, independent of the criteria used for data evaluation. The difference between the two Vogel temperatures corresponds to results for samples with other molecular weight and polydispersity from the literature. The T ∞FT 〈T ∞α relation is discussed in terms of short (α) and long (FT) dynamic glass transitions in entangled polymers. The relation is explained by preaveraging of the energy landscape for the long flow transition by the short glass transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366824
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    Modeling spurt and stress oscillations in flows of molten polymers (1997)
    Springer
    Rheologica acta 36 (1997), S. 110-127 
    Details
    ISSN: 1435-1528
    Keywords: Spurt ; oscillations ; wall slip ; capillary flows ; stick-slip ; critical shear stress ; loss of fluidity ; hardening parameter ; extrudate distortion ; melt fracture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The paper presents an approach for modeling polymer flows with non-slip, slip and changing non-slip — slip boundary conditions at the wall. The model consists of a viscoelastic constitutive equation for polymer flows in the bulk, prediction of the transition from non-slip to sliding boundary conditions, a wall slip model, and a model for the compressibility effects in capillary polymer flows. The bulk viscoelastic constitutive equation contains a hardening parameter which is solely determined by the polymer molecular characteristics. It delimits the conditions for the onset of solid, rubber-like behavior. The non-monotone wall slip model introduced for polymer melts, modifies a slip model derived from a simple stochastic model of interface molecular dynamics for cross-linked elastomers. The predictions for the onset of spurt, as well as the numerical simulations of hysteresis, spurt, and stress oscillations are demonstrated. They are also compared with available data for a high molecular weight, narrow distributed polyisoprene. By using this model beyond the critical conditions, many of the qualitative features of the spurt and oscillations observed in capillary and Couette flows of molten polymers, are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366817
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  • 91
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    Isothermal elongational behavior of liquid-crystalline polymers and LCPs based blends (1997)
    Springer
    Rheologica acta 36 (1997), S. 152-159 
    Details
    ISSN: 1435-1528
    Keywords: Elongational flow ; liquid crystalline polymer ; polymer blends
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The rheological behavior of two flexible thermoplastics, Nylon-6 (Ny) and bisphenol-A polysulfone (PSu), and two wholly aromatic liquid crystalline polymers, Vectra-A900 (VA) and Vectra-B950 (VB), as well as that of Ny/VB and PSu/VA blends with 10% LCP, has been investigated by the use of capillary viscometers equipped with cylindrical dies having different length-to-diameter ratios. The elongational viscosity of all materials was calculated, from the results of isothermal measurements carried out at 290°C, by means of the Cogswell's analysis, based on the estimation of the pressure drop due to the converging flow at the die inlet. The behavior in elongational flow was compared with the rheological behavior in shear flow conditions. It was found that the elongational viscosities of VA and VB are very large and account for a fairly marked pressure drop at the die entrance, due to the orientation of the LCP domains taking place in the converging flow zone. For these materials, the ratio of the elongational viscosity to the Newtonian shear viscosity is up to two orders of magnitude higher than the value expected on the basis of the Trouton rule. For the flexible resins, the Trouton ratio is 3 and ca. 3–10, are common values for high molar mass linear polymers. The addition of 10% LCP into the flexible resins strongly increases their elongational viscosity and makes the blends resemble neat LCPs in their extensional flow behavior. In shear flow, on the contrary, the addition of LCP was shown to induce a marked reduction of the melt viscosity, even when, as for the Ny/VB blend, the LCP is more viscous than the matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366821
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  • 92
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    Announcements (1997)
    Springer
    Rheologica acta 36 (1997), S. 202-203 
    Details
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366826
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  • 93
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    Strain hardening of fibrin gels and plasma clots (1997)
    Springer
    Rheologica acta 36 (1997), S. 262-268 
    Details
    ISSN: 1435-1528
    Keywords: Fibrin ; viscoelasticity ; strain hardening ; clot retraction ; platelets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Biological macromolecules have unique rheological properties that distinguish them from common synthetic polymers. Among these, fibrin has been studied extensively to understand the basic mechanisms of viscoelasticity as well as molecular mechanisms of coagulation disorders. One aspect of fibrin gel rheology that is not observed in most polymeric systems is strain hardening: an increase in shear modulus at strain amplitudes above 10%. Fibrin clots and plasma clots devoid of platelets exhibit shear moduli at strains of approximately 50% that are as much as 20 times the moduli at small strains. The strain hardening of fibrin gels was eliminated by the addition of platelets, which caused a large increase in shear storage modulus in the low strain linear viscoelastic limit. The reduction in strain hardening may result from fibrin strand retraction which occurs when platelets become activated. This interpretation is in agreement with recent theoretical treatments of semi-flexible polymer network viscoelasticity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366667
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    Design of sparse matrix representations for the propagator used in the BPM and directional wave field decomposition (1997)
    Springer
    Optical and quantum electronics 29 (1997), S. 179-197 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Directional wave field decomposition can be accomplished with the aid of pseudo-differential operators. A fast numerical scheme requires sparse matrix representations of these operators. This paper focuses on designing sparse matrices for the propagator while keeping the accuracy high at the cost of ignoring critical-angle phenomena. The matrix representation follows from a rational approximation for the square root operator and the derivatives. The parameterization thus introduced lends itself to an overall optimization procedure that minimizes the errors for a chosen discretization rate. As such, the approach leads to an accurate propagator up to the (local) critical angle on a coarse numerical grid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018554105794
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    On the classification of discrete modes in lossy planar waveguides: the modal analysis revisited (1997)
    Springer
    Optical and quantum electronics 29 (1997), S. 243-262 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In integrated-optical components such as integrated optical detectors or semiconductor light amplifiers, multilayer dielectric waveguiding structures occur in which some layers may be strongly lossy or may have gain. In such structures, the classification of the guided modes may become impossible. This paper reviews the modal analysis in which modes are only considered in connection with their possible excitation with a current line-source. Starting from the lossless situation, the analysis is extended to the lossy case and the details of the classification problem are investigated numerically. It was found that the validity of a unique classification is always limited. For that reason it is investigated, whether the classification problem might be due to the fact that in the time-harmonic formulation, the physical requirement of causality has been lost. To test this hypothesis, wave propagation is investigated along lossy waveguides in the timeLaplace-transform domain and using Lerch's causality theorem. It surprisingly turns out that in the time-Laplace-transform domain, the discrete part of the longitudinal spectrum does not exist, so that the test of the hypothesis is not conclusive. The classification problem of guided modes in strongly lossy waveguides is still an open problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018562307611
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    Application of a fully vectorial beam propagation method (1997)
    Springer
    Optical and quantum electronics 29 (1997), S. 313-322 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A new vectorial beam propagation method has successfully been applied to a passive polarization splitter and a passive polarization converter on InGaAsP/InP. The propagating fields are calculated and the power attenuation is evaluated. The calculated crosstalk values of the splitter are in good agreement with the realized best performance. A complete polarization conversion in the converter has also been simulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018522626266
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  • 97
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    Modelling of cascaded Mach-Zehnder add/drop multiplexer with film mode matching method (1997)
    Springer
    Optical and quantum electronics 29 (1997), S. 343-348 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A semi-analytical method for modelling cascaded Mach-Zehnder add/drop multiplexers with a mode solver based on the film mode matching method is presented. Examples for an inverted rib waveguide structure are given. They focus on the polarization dependence, etching tolerances and on the coupling which takes place at the circular access waveguides of each directional coupler.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018578711245
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    Influence of the type of light polarization on photoinduced processes (1997)
    Springer
    Optical and quantum electronics 29 (1997), S. 405-412 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We investigate the influence of the type of light polarization (linear or circular) on the efficiency of non-linear optical processes in photoanisotropic materials. A theoretical model of photoprocesses in materials in which optical non-linearity is related to absorbing centres with intrinsic linear anisotropy is constructed. Theoretical calculations show that the photostationary concentration of the photoproducts (and the mean values of the non-linear changes in optical constants) in these materials is higher if the exciting light is circularly polarized. Experimental results on non-linear processes in samples of fluorescein incorporated in orthoboric acid and in azodye/polymer layers are in good agreement with the theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018587013063
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    10 Gbits−1 optically amplified single-channel systems operating in links encompassing conventional step-index fibres (1997)
    Springer
    Optical and quantum electronics 29 (1997), S. 21-34 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In this work a numerical investigation is reported on the propagation regimes that allow single-channel systems to obtain the maximum capacity in links with optical amplification encompassing conventional step-index fibres. Solitons and NRZ signals are considered. We show how the periodical introduction of pieces of dispersion compensating fibres can greatly improve the system performance. The polarization properties of the signals are investigated to increase the system performance and
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018521231293
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    FDTD modelling of spatial soliton propagation (1997)
    Springer
    Optical and quantum electronics 29 (1997), S. 233-241 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The finite difference time domain method is used as a tool to model non-linear optical devices. Following this approach, Maxwell's equations are directly integrated in the time domain, avoiding any mathematical approximation. As an example, spatial soliton propagation and interaction will be modelled by the FDTD technique. Some new results will be discussed, to highlight the envisaged breakthroughs allowed by the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018510323541
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