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  • 11
    Electronic Resource
    Electronic Resource
    Static and dynamic light scattering from polystyrene/cyclohexane/toluene solutions (1999)
    Springer
    Polymer bulletin 43 (1999), S. 261-267 
    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 Static and dynamic light scattering data from polystyrene in cyclohexane and toluene mixed solvent are reported. It is found from the Zimm plot analysis of the static data that if the subtraction of solvent signal is made properly then, the results are consistent with those in toluene indicating a preferential adsorption of the good solvent. Contin analysis of the dynamic data yields two modes unlike the dynamics of polystyrene in single solvent solutions which exhibit a single mode at all polymer concentrations covered here. A possible interpretation of the fast and slow modes is given. Keywords: Mixed Solvent; Dilute Polymer Solution; Preferential Adsorption; Static and Dynamic Light Scattering; Relaxation Modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050561
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  • 12
    Electronic Resource
    Electronic Resource
    Hydrodynamic screening of ring copolymer solutions (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 981-984 
    Details
    ISSN: 0887-6266
    Keywords: hydrodynamic screening ; ring copolymer ; first cumulant ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relaxation frequency of the dynamic correlation function for a diblock cyclic copolymer in solution in the zero average condition is calculated in the presence of hydrodynamic interaction. The latter is introduced through the screened Oseen tensor where the hydrodynamic screening length is used as a parameter to determine the range of screening. Substantial differences with the case of linear homopolymer are found, especially in the low q range where the dynamics are much faster and correspond to nondiffusive processes as usually is the case for copolymer systems. As the screening length decreases the dynamics approach the Rouse behavior and the minimum of the relaxation frequency shifts to lower values. The proportionality constant of the relaxation frequency in the intermediate q range Γ(q) → q3/(kBTη0) is also investigated as a function of the screening length. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320602
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  • 13
    Electronic Resource
    Electronic Resource
    Theory of static scattering from polymer mixtures. The case of polystyrene/polydimethylsiloxane/poly(methyl methacrylate)/toluene (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 4 (1995), S. 53-65 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The static scattering properties of four-component polymer mixtures are examined starting from the general equation extending the random phase approximation to multicomponent systems first proposed by Benoit. The results are compared with the light scattering data reported recently by Strazielle and coworkers for polystyrene/polydimethylsiloxane/poly(methyl methacrylate)/toluene mixtures. The present formalism provides a more rigorous treatment of these data, and a good agreement is obtained without adjustable parameters. This method provides a definition of the apparent interaction parameter used by Strazielle et al. and describes its correlation with various relevant quantities characterizing the mixture. It predicts in particular the variation of this parameter with the concentration of poly(methyl methacrylate), which was not possible in the earlier work. Various other important properties of the mixture are investigated such as the critical concentration for phase separation and the apparent radius of gyration.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1995.040040103
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  • 14
    Electronic Resource
    Electronic Resource
    On the phase behavior of blends of polymers and nematic liquid crystals (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 7 (1998), S. 599-611 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase behavior of mixtures of polymers and nematic liquid crystals (LC) is investigated. Two types of systems are examined. The first one deals with blends in which the polymer is made of linear chains. In this case, a systematic study of the effects of various parameters on the phase diagrams is performed. In particular, it is shown how increasing the polymer size and/or the LC molecule size increases the miscibility gap of the mixture. It also reduces the region where a single nematic phase is observed in the presence of a tiny amount of polymer. Likewise, the relative effects of the isotropic and the nematic interaction parameters on the phase diagrams are examined. The second part of this investigation deals with blends involving crosslinked polymers. Here, substantial differences are observed as compared to the case where the polymer components are made of linear chains. These differences are illustrated by showing the phase diagrams in similar conditions for both blends. Unlike the case of a linear polymer matrix, it is observed that the single nematic phase and the nematic-isotropic spinodal branches are absent from the phase diagram of crosslinked polymers. This results into significant distortions of the phase diagram. In order to highlight all these effects, examples representing hypothetical blends are considered. These examples are chosen for illustration of the results in which the choice of numerical parameters is made consistently with the existing values in the literature which makes comparison with published data possible.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Stability analysis and scattering properties of charged crosslinked blends in solution (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 3 (1994), S. 557-566 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase behavior and scattering properties of crosslinked charged polymer blends in solution are examined. De Gennes' analogy between the effects of crosslinks in a network and electrostatic charges in a dielectric medium on the scattering properties and the phase behavior of crosslinked polymer blends is used. This analogy is extended to include the effects of screening in order to improve its agreement with the experimental data in the small q range. The excluded volume interactions are explicitely introduced through the blob model. The enhancement of compatibility of the mixture and the increase of its rigidity constant are evaluated in certain cases. The limit of neutral polymers is discussed because it corresponds to the case of charged mixtures in the presence of excess salt. The kinetics of the microphase separation transition is briefly discussed. A dynamical model including the long range hydrodynamic interaction is presented. The relaxation frequency of the stable modes and the growth rate of unstable ones are also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1994.040030303
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  • 16
    Electronic Resource
    Electronic Resource
    Elastic and quasielastic light scattering from mixtures of three polymers and a solvent: The effects of polymethylmethacrylate concentration and molecular weight on the properties of polystyrene/polydimethylsiloxane/toluene solutions (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 823-832 
    Details
    ISSN: 0887-6266
    Keywords: polymer solution ; ternary systems ; quaternary systems ; classical light scattering ; quasielastic light scattering ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Elastic and quasi-elastic light scattering data obtained from PS/PDMS/PMMA/toluene mixtures are reported. Several systems characterized by different concentrations and different molecular weights of PMMA are considered. For each of these systems, a systematic investigation is performed as a function of the scattering angle and the concentration of the PS/PDMS mixture using both techniques. The PMMA does not contribute directly to the scattered light since its increment of refractive index is zero. However the data show that its presence modifies substantially the apparent interaction parameter of PS and PDMS and the single diffusion coefficient of these polymers in the solution. The variations of these quantities with the concentration and molecular weight of PMMA are obtained. The data are analyzed within a simplified model combining based on the random phase approximation and the Rouse dynamics for ternary polymer mixtures. © 1995 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090330511
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  • 17
    Electronic Resource
    Electronic Resource
    Viscosity of weakly charged polyelectrolyte solutions: The screening of hydrodynamic interactions (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 3 (1994), S. 73-77 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mode-mode coupling approximation (MMCA) is used to describe the behavior of the reduced viscosity of weakly charged polyelectrolyte solutions in the presence of screening of hydrodynamic interactions. This effect is introduced through a dynamic correlation length ζH in the Oseen tensor description. The results show that as ζH goes from zero (Rouse model) to infinity (Zimm model), the general qualitative behavior of ηr as function of the polyelectrolyte concentration Cp does not change but its value decreases significantly with a slight shift in the peak position toward higher Cp values.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1994.040030106
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  • 18
    Electronic Resource
    Electronic Resource
    Scattered intensity by a cross-linked polymer blend (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 4 (1995), S. 67-76 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cross-linked mixtures of polystyrene and poly(vinyl methyl ether) exhibit a non-vanishing zero-angle intensity in small-angle neutron scattering experiments. A possible explanation is that fluctuations in composition in the mixture may be frozen by the presence of cross-links. Assuming this, we introduce a screening length κ by the condition that the scattered intensity should not be changed by cross-linking. We find κ2 ∼ C/(χ - χi), where C is an elastic constant, χ and χi, respectively, the inverse temperature and that where cross-linking is performed. When the temperature is varied, we find three regimes. In the first one, the scattered intensity is monotonously decreasing. In the second one, it has a finite maximum. In the last one, the maximum eventually diverges.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1995.040040104
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  • 19
    Electronic Resource
    Electronic Resource
    Polymer blends, copolymers and networks. Scattering properties and phase behavior (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 6 (1997), S. 197-235 
    Details
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase behavior and scattering properties of polymer blends, copolymers and networks in solution and in bulk are examined. The theoretical framework used here is based upon the extension of the random phase approximation to polymers proposed by de Gennes and its application to chains with various architectures. The case of blends containing stiff chains is considered and the effect of nematic interaction on the phase behavior and scattering properties is discussed. The compressibility problem is reviewed in connection with the free volume theory models. The coupling between density and composition fluctuations is examined together with the effects of pressure on the structural and thermodynamic properties of blends. The dynamics of copolymers are also examined in the light of the new developments both from the theoretical and experimental fronts. The extent to which the chain architecture affects phase behavior, static scattering and dynamic behavior is discussed. A particular emphasis is put on the case of cyclichomopolymers and copolymers. Free chains in a network and crosslinked blends are also a subject of particular interest in this paper. The interplay between macrophase and microphase transitions due to the crosslinks and the electrostatic forces for charged polymers is also considered. De Gennes' analogy betwen the elastic restoring forces in the network and the Coulomb forces in the dielectric medium is generalized by including the screening phenomenon. This generalization is required in order to account for the experimental observations in the low momentum transfer range. Following Briber et al., it is argued that the new screening length can be related to the initial fluctuations at the temperature of crosslinking.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1997.040060114
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  • 20
    Electronic Resource
    Electronic Resource
    Statics and dynamics of single chains in polymer blends and copolymer melts  -  results beyond the random phase approximation (1992)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Theory and Simulations 1 (1992), S. 25-30 
    Details
    ISSN: 1018-5054
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We present new results on the behaviour of single chains in homo-and copolymer blends which are beyond the rendom phase approximation (RPA). The radius of gyration of a chain in the blend was found to depend strongly on the interactions as well as the effective diffusion constant of a single chain in the blend or copolymer melt. Note that these results cannot be obtained in the original formulation of the RPA. They are based on the effective Hamiltonian of the chain in the medium. In the equation found for the self diffusion constant of a single chain, Ds, the second term is directly the value of the effective potential at zero wave vector. Thus the measurement of Ds would detect the screened potential at q = 0. Experimental verification of these results is in progress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1992.040010103
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