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  • 1
    Electronic Resource
    Electronic Resource
    Dielectric relaxation in disordered poly(isoprene-styrene) diblock copolymers near the microphase-separation transition (1992)
    s.l. : American Chemical Society
    Macromolecules 25 (1992), S. 5277-5282 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00046a026
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  • 2
    Electronic Resource
    Electronic Resource
    Phase separation kinetics in a binary mixture of polyethylene glycol and polypropylene glycol studied by light scattering after a pressure jump: Pinning of domain growth by hydrogen bond structures (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 5217-5226 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The phase separation kinetics of fluid mixtures of polyethylene glycol/polypropylene glycol (a system with an upper critical mixing point) is studied after a pressure jump from the homogeneous one-phase region into the two-phase region of the phase diagram. The growth of the emerging domains of the coexisting phases is observed by small angle laser light scattering. In additional measurements the pressure dependence of the phase separation temperature is analyzed. In the kinetic experiments the time-dependent structure function is detected for a mixture with near-critical as well as for a mixture with off-critical composition. For the near-critical mixture an increase of the maximum of the scattering intensity with time has been found, which qualitatively is typical for the intermediate to late stages of spinodal decomposition. A closer analysis of the late stages reveals two maxima in the structure factor with their own set of growth exponents for the scattering vector and for the intensity. The data of the low q maximum are compatible with a two-dimensional growth process which is interpreted as a demixing process in a wetting layer. The data of the high q maximum are according to a three-dimensional process. It is assumed that this maximum reflects the demixing process in the bulk phase. The values of the three-dimensional growth exponents, which are considered to be late stage values, are not compatible with observations on other fluid systems but are close to those for solid systems or, in general, for systems with suppressed hydrodynamic interactions. For the mixture with an off-critical composition the structure function remains constant for larger times (pinning effect). The occurrence of a pinning effect in samples of relatively low molecular weight Mw (Mw≤1019 g/mol) and the apparently suppressed hydrodynamic interactions in a fluid sample are explained with specific interactions caused by hydrogen bonding (i.e., transient entanglement or a dynamic network). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474885
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of stochastic environments of Gaussian chains on dynamic shear and bulk properties (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 2772-2776 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theory of dynamic bulk and shear viscosity in polymer systems is presented. To overcome the neglect due to the preaveraged hydrodynamic interaction in the theory of dynamic viscoelastic properties of polymers, a perturbation term, which includes the influence of external environments coupled to the velocity field, was introduced in the dynamic equation. The influence of this additional perturbation term to both dynamic bulk and shear properties was studied. This nonthermodynamic contribution modifies the Rouse spectrum. It was shown that the relaxation time spectrum is the same for the dynamic bulk ηV and shear viscosity ηS, whereas the ratio between the both quantities was found to exceed the value ηV/ηS=2/3 for pure viscous drag. The theoretical results are compared with experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463068
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrasonic shear wave reflection method for measurements of the viscoelastic properties of polymer films (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1536-1542 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report a shear wave reflection technique which allows time- and temperature-dependent measurements of the complex dynamic shear modulus (G*=G′+iG′′) or the dynamic shear viscosity (ηs′) in the ultrasonic frequency range (3–40 MHz). The shear wave reflection method developed by Mason et al. [Phys. Rev. 75, 936 (1949)] was adapted to the possibilities of the high-frequency digital technique. A conventional single-frequency pulse-burst system and a broadband pulsed ultrasonic spectroscopic system using Fourier analysis for detection of phase and amplitude changes of the reflected signals are described alternatively. Due to digital analysis of the received signal it was possible to achieve a simplification of the experimental setup and to extend the limits of the shear wave reflection technique to about one Gigapascal (100 μm film thickness) or to minimum film thickness of about 10 μm (G′〈10 MPa). Furthermore, it is possible to monitor time-dependent isothermal processes or reactions with the setup. The basic features of the two different techniques are presented together with brief experimental results on film formation from aqueous polychloroprene dispersions and of the crystallization kinetics in the films. Furthermore, temperature-dependent studies of melting and crystallization on semicrystalline polychloroprene and of the glass transition behavior of amorphous butyl acrylate/styrene copolymer films are reported. The importance of the method is discussed for both investigations of fundamental questions (e.g., film formation, reaction kinetics, or phase transitions) and technological assessment (glues, paints, etc.). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147643
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  • 5
    Electronic Resource
    Electronic Resource
    Spectroscopic investigations on aqueous solution of poly(oxyethylene) - poly(oxypropylene) - poly(oxyethylene) triblockcopolymers
    Amsterdam : Elsevier
    Journal of Molecular Structure 219 (1990), S. 365-370 
    Details
    ISSN: 0022-2860
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-2860(90)80083-V
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  • 6
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR investigation of vinyl-chloride/ vinyl-acetate copolymers (1981)
    Springer
    Polymer bulletin 5 (1981), S. 299-303 
    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: Summary Copolymers of vinyl chloride with vinyl acetate have been studied by Carbon 13 NMR specroscopy to determine the influence of the copolymerization on the tacticity of PVC sequences. Diad and triad resonances have been assigned in terms of constitutional as well as of configurational sequences. The syntacticity of the PVC sequences appears to decrease with increasing comonomer content. This decrease might be caused by a steric hindrance which would favour a more atactic addition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254717
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  • 7
    Electronic Resource
    Electronic Resource
    Curing kinetics of phase separating epoxy thermosets studied by dielectric and calorimetric investigations: A simple model for the complex dielectric permittivity (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2461-2470 
    Details
    ISSN: 0887-6266
    Keywords: dielectric relaxation spectroscopy ; thermosets ; interpenetrating polymer networks ; curing reaction ; temperature-modulated differential scanning calorimetry ; glass transition ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dielectric relaxation spectroscopy (3 kHz ≤ ƒ ≤ 3 MHz), differential scanning calorimetry, and temperature-modulated calorimetry have been performed during isothermal curing of an epoxy network (diglycidylether of bisphenol A crosslinked with diaminodiphenyl methane), and of two thermoplast modified epoxy resins (semi-interpenetrating polymer networks) consisting of the epoxy network component and different amounts (10 and 20 wt %) of a linear high Tg polymer (polysulfone or polyethersulfone). During reaction, the homogeneous-mixtures phase separate into an epoxy-rich and a linear polymer-rich phase with different mobilities of the electrical dipoles. The complex dielectric permittivity is composed of a contribution from the ionic dc-conductivity and a contribution from relaxations of the permanent electrical dipoles in the two phases. The decrease of the dc-conductivity in the initial stage of cure is related to the time for gelation or vitrification. The contribution of the dipole relaxations to the dielectric permittivity reflects an increase of the relaxation times with curing time for both phases. The time-dependent changes in the complex dielectric permittivity are described by a simple two-phase model based on two Havriliak-Negami functions combined with Vogel-Fulcher equations for the description of the curing-time dependence of the relaxation times. The increase of the relaxation times in the phases during isothermal curing is incorporated by time-dependent Vogel temperatures. The latter are related to the time evolution of the glass-transition temperatures in the two phases measured independently by calorimetry. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2461-2470, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Ultraschalluntersuchungen an Poly(propylenoxid) - Vergleich von linearen und sternförmigen Molekülen (1986)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 37 (1986), S. 733-736 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ultrasonic attenuation was measured with linear and star-shaped poly(propylene glycoles) in a frequency range from 0.1 to 100 MHz. Both samples exhibit the same relaxational behaviour qualitatively. The differences of the absorption values can be explained by differences of molecular mass. An additional contribution assigned to the star structure was not detected.
    Notes: Ultraschallabsorptionsuntersuchungen wurden an linearem und sternförmigem Poly(propylenglykol) in einem Frequenzbereich von 0,1 bis 100 MHz durchgeführt. Beide Proben zeigen qualitativ das gleiche Relaxationsverhalten. Die Unterschiede in der Absolutgröße der Absorption können durch die Unterschiede der Molekülmasse beider Proben erklärt werden. Ein zusätzlicher Absorptionsmechanismus durch die Sternstruktur wurde nicht nachgewiesen.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1986.010371116
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  • 9
    Electronic Resource
    Electronic Resource
    Ultraschalluntersuchungen zum Einfluß des Lösungsmittels auf die molekulare Beweglichkeit in Polymerlösungen (1986)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 37 (1986), S. 487-491 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The influence of different solvents on the molecular mobility of poly(vinyl chloride) and poly(vinyl acetate) solutions has been studied by measurements of ultrasonic absorption. In the case of PVC the solvents cyclohexanone, methylethylketone and 1,4-dioxan were used. PVAC was investigated in cyclohexanone, toluene, acetone and methanol. The influence of the solvents on the ultrasonic absorption is discussed in different terms of the relaxation (local rotational isomeric processes, cooperative rotational isomeric processes, normal mode processes, entanglements, and associates).
    Notes: An Lösungen von Poly(vinylchlorid) und Poly(vinylacetat) wurden Ultraschallabsorptionsmessungen zur Untersuchung des Lösungsmitteleinflusses auf die molekulare Beweglichkeit durchgeführt. Als Lösungsmittel für PVC wurden Cyclohexanon, Methylethylketon und 1,4-Dioxan verwendet. PVAC wurde in Cyclohexanon, Toluen, Aceton und Methanol untersucht. Der Einfluß des Lösungsmittels auf die Ultraschallabsorption wird mit unterschiedlichen Wirkungen auf die verschiedenen Relaxationskomponenten (lokale Rotationsisomerien, kooperative Rotationsisomerien, Normalmodenprozesse, „entanglements“ und Assoziate) diskutiert.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1986.010370804
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  • 10
    Electronic Resource
    Electronic Resource
    Ultrasonic absorption in solutions of homo- and copolymers of vinyl chloride and vinyl acetate (1986)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 37 (1986), S. 491-496 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Ultraschallabsorption in Lösungen von Poly(vinylchlorid), Poly(vinylacetat) und einer Reihe von Vinylchlorid-Vinylacetat-Copolymeren in Cyclohexanon wurde im Frequenzbereich von 0,3 bis 120 MHz untersucht. Die Resultate zeigen, daß die Relaxationsspektren mit zwei Relaxationsprozessen angepaßt werden können. Diese Prozesse können durch das Auftreten von Konformationsanderungen unterschiedlicher Kooperativität erklärt werden. Der Vergleich der thermodynamischen Parameter mit Konformationsenergierechnungen unterstützt die Annahme von lokalisierten Umlagerungen einer Bindung als Elementarprozeß. Die Ultraschallspektren der Homopolymerlösungen werden mit denen der statistischen und Pfropfcopolymere verglichen.
    Notes: The ultrasonic attenuation in solutions of poly(vinyl chloride), poly(vinyl acetate) and different vinyl chloride/vinyl acetate copolymers dissolved in cyclohexanone was investigated. The results indicate that the relaxation spectra can be resolved by curves with two relaxation times. These processes can be explained by the presence of conformational changes of different degree of cooperativity. Comparison of the thermodynamic parameters with conformational energy calculations supports the assumption that the elementary process is a localized single-bond process. The ultrasonic spectra of the homopolymers solutions are compared with those for statistical and graft copolymers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1986.010370805
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