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  • Articles  (74)
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  • American Chemical Society
  • Cambridge University Press
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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1083-1087 
    ISSN: 0887-6266
    Keywords: polyurethane ; diffusion ; wide-angle x-ray diffraction ; phase mixing ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An analysis of the diffusion of toluene through polyurethane based on bis (p-cyclohexyl diisocyanate), poly(tetramethylene glycol) 1000, and 1,4-butane diol, subjected to varied degrees of elongation by stretching, is presented. The diffusion coefficient is increased by 60% in polymers drawn to 200% and above. Beyond 400% elongation, the diffusion coefficient attained a constant value. Associated changes are observed in the wide-angle x-ray diffraction pattern. These diffusion and x-ray changes are correlated with restructuring of the polymer induced by stretching. © 1993 John Wiley & Sons, Inc.
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  • 2
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1273-1283 
    ISSN: 0887-6266
    Keywords: polynorbornenes ; permeation ; diffusion ; sorption ; plasticization ; spin probes ; free volume ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Gas sorption properties, permeability coefficients, and diffusion coefficients of a series of norbornene polymers are presented. Introduction of the Si(CH3)3 group into the polynorbornene (PNB) backbone chain results in significant increases in glass transition temperature, permeability, and diffusion coefficient for a number of gases (H2, O2, N2, CO2, CH4, C2H6). The transport properties and sorption isotherms for poly(5-trimethylsilyl norbornene) (PTMSNB) are very similar to those for poly(vinyltrimethyl silane) (PVTMS), which contains the same side-chain group but differs from PTMSNB by the structure of its main chain. For another silicon-containing polymer poly[5-(1,1,3,3-tetramethyl-1,3-disilabutyl) norbornene] (PDSNB) having a bulkier side-chain group, the glass-transition temperature is decreased in comparison with that of PNB, presumably owing to self-plasticization. Both silicon-containing norbornene polymers (PTMSNB and PDSNB) have permeability coefficients for “rapid” gases like H2 or CO2 of about 102 Barrer. The high values of the Langmuir sorption capacity C′H for PTMSNB and PVTMS, as well as the high diffusivity and mobility of spin probes in these polymers, were attributed to a large free volume related to the bulky Si(CH3)3 groups attached directly to the main chain. © 1993 John Wiley & Sons, Inc.
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  • 3
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 131-139 
    ISSN: 0887-6266
    Keywords: hydrogen bond ; gas sorption ; gas transport ; gas permeability ; diffusion ; polymer blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The gas sorption behavior of CO2, C2H6, and CH4, and the gas transport behavior of CO2 and CH4, were examined for polyethersulfone (PES), polyhydroxyether, and four miscible blends containing 20, 40, 60, and 80 wt % PES. The 40 wt % PES blend exhibited the lowest sorption levels and the lowest permeabilities for all of the gases. Application of the dual-mode sorption model revealed negative deviations for the Henry's law parameter kD that were larger than those observed for blends relying on van der Waals or simple polar interactions. Also, the magnitude of the blend interaction parameter obtained from the gas sorption data and the volume of mixing were both more negative in the hydrogen-bonded blend. Diffusion coefficients at infinite dilution and from the dual mode/partial immobilization model exhibited minima at 40 wt % PES, as did the fractional free volume, a measure of chain packing ability. © 1994 John Wiley & Sons, Inc.
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  • 4
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1785-1797 
    ISSN: 0887-6266
    Keywords: diffusion ; hydrodynamics ; transport properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Higher order hydrodynamics interactions are short-range modifications to the Oseen tensor Tij and its self-interaction counterpart Tii. They differ from the Oseen tensor in having terms of higher order than the first in a/R, a being a bead radius and R being a bead-bead distance. Effects of higher order hydrodynamic interactions on whole chain-whole chain hydrodynamic interactions are here computed. Higher order hydrodynamic interactions are shown to lead to a concentration dependence of the diffusion and friction coefficients of a free monomer. However, while higher order interactions make contributions of the same nature to the drag coefficients of a monomer and of a whole chain, the contributions are not simply multiplicative, removing a justification for the common practice of correcting polymer solution transport data for “monomer friction effects” via a normalization with data on friction coefficients of free monomers. © 1993 John Wiley & Sons, Inc.
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  • 5
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 785-789 
    ISSN: 0887-6266
    Keywords: PMMA ; PVF2 ; diffusion ; solid-state NMR ; cross-depolarization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A previously published new solid-state nuclear magnetic resonance (NMR) method is applied to the interdiffusion of poly(methacrylate) (PMMA) and poly(vinylidene fluoride) (PVF2) above their Tg. Via a variation of the cross-polarization technique magnetization is transferred from protons to fluorines. When this magnetization is made to disappear at the fluorine sites, only those protons that are distant from fluorines greater than the distance over which cross-polarization functions will retain their magnetization. In this way we detect the fraction of PMMA near (ca. 20 Å) PVF2. Starting from sheets of PMMA and PVF2, which are then heated at 190°C for a variable time, and applying the above technique, we can determine the fractions of PMMA and PVF2 that have diffused within a distance of a few Å of each other. The intrinsic diffusion coefficients of PMMA and PVF2 determined from such experiments compare well with literature data. Initial attempts to fit the experimental data suggest that the concentration dependence of the diffusion coefficients cannot be neglected. © 1994 John Wiley & Sons, Inc.
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  • 6
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 487-494 
    ISSN: 0887-6266
    Keywords: gas separations ; diffusion ; gas sorption ; spirobiindane bisphenol ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transport properties of pure gases in polycarbonates, polyesters, and polyetherimides based on 6,6′-dihydroxy-3,3,3′,3′-tetramethyl-1,1′-spiro biindane (SBI) and bisphenol-A (BPA) are compared at 35°C. The SBI monomer contains two spiro-linked five-membered rings which are fused to the phenyl rings at the meta and para positions to the hydroxyl groups. This molecular structure gives SBI-based polymers with higher fractional free volume (FFV) and lower intramolecular motions as compared to the BPA-based analogs. The inhibition of chain packing due to the SBI moiety yields polymers with much higher permeabilities for all the gases studied, despite the hinderance of mobility associated with the SBI structure. Simultaneous increase in selectivity was also observed for some gas pairs. Oxygen permeabilities up to 5.9-fold higher with increases of up to 13% in O2/N2 selectivities were observed for a polyester based on SBI as compared to its analog based on BPA. Higher permeabilities of up to 4.3-fold for He and up to 4.8-fold for CO2 were observed due to the substitution of SBI for BPA. Not surprisingly, lower values of He/CH4 and CO2/CH4 selectivities were obtained for the more open SBI-containing polymers. The changes in fractional free volume and inhibition of small-scale mobility for some materials caused by the SBI moiety were measured and used in the interpretation of the gas transport properties. The individual contributions of diffusivity and solubility to the overall transport behavior of the polymers are discussed and correlated to the structural alterations caused by the SBI substitution for BPA monomer. © 1995 John Wiley & Sons, Inc.
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  • 7
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 2175-2179 
    ISSN: 0887-6266
    Keywords: phase inversion ; modeling ; diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 8
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2723-2730 
    ISSN: 0887-6266
    Keywords: polystyrene ; poly(vinylmethylether) ; blends ; carbon dioxide ; sorption ; diffusion ; plasticization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The sorption and transport properties of CO2 in miscible PS/PVME blends at 20°C are reported as a function of pressure from 1 to 15 atm. The complex shape of isotherms for glassy blends and the concentration-dependent diffusion coefficient for rubbery blends reveal a plasticization by sorbed CO2. The significant depression in Tg has to be taken into account in the analysis of the sorption data. Diffusion coefficient for CO2 passes through a minimum when plotted against the blend composition. Such a behavior can be quantitatively related to the negative volume mixing of the PS/PVME system in the framework of the theories based on unoccupied volume. © 1996 John Wiley & Sons, Inc.
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  • 9
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1737-1746 
    ISSN: 0887-6266
    Keywords: free volume ; dual mode ; diffusion ; glassy polymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The development of a new model for the diffusion of gas molecules in glassy polymers is presented which utilizes concepts from free volume theory and relies on a dual-mode interpretation of sorptive dilation in glassy polymers. Three assumptions are made in the development of the model. First, the free volume available for molecular transport processes is taken as constant below the glass transition temperature. Second, two populations of gas molecules are assumed to exist - one which contributes to the maintenance of an iso-free volume state upon sorptive dilation and one which does not contribute owing to sorption into regions of unrelaxed volume. Third, the former population is assumed to be mobile while the latter is not. The resulting model predicts, at constant temperature, a diffusion coefficient that is independent of solute volume fraction. This is in contrast to the widely used dual-mode sorption model with partial immobilization for gas transport in glassy polymers which leads to a diffusion coefficient that is dependent on solute mole fraction through the molar gas concentration. The new model is used to interpret gas transport data from permeation experiments for carbon dioxide, methane, and ethylene in three polycarbonates. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1737-1746, 1997
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  • 10
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1261-1267 
    ISSN: 0887-6266
    Keywords: FTIR-ATR spectroscopy ; gravimetric sorption ; diffusion ; polymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this study, vapor sorption FTIR-ATR (Fourier Transform Infrared Attenuated Total Reflectance) spectroscopy was combined with a conventional gravimetric sorption balance to examine diffusion in polymers. Mutual diffusion coefficients of methyl ethyl ketone in polyisobutylene were measured using both methods at various penetrant activities and temperatures in the range 40-60°C. Actual penetrant concentrations were determined from the sorption balance. The diffusion coefficients from the two techniques agree very well with each other. In addition, the diffusivity data from both techniques could be correlated successfully as a function of temperature and concentration with the Vrentas and Duda free-volume model. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1261-1267, 1997
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  • 11
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2435-2445 
    ISSN: 0887-6266
    Keywords: diffusion ; interphase ; composition profiles ; interdiffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An experimental method to determine interphase composition profiles in amorphous polymers pairs and polymer-solvent pairs is presented. The method is based on the measurement of dynamic mechanical properties of slender composite beams, and well-established properties of amorphous polymer homogeneous blends and solutions. The method does not require tracers. A simple calibration procedure is included in the description, and some results for a polystyrene-polystyrene pair are used to illustrate the method application. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2435-2445, 1997
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  • 12
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2503-2510 
    ISSN: 0887-6266
    Keywords: rheology ; diffusion ; star-branched polymers ; polyisoprene ; terminal viscosity ; molecular weight dependence ; temperature dependence ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recent experimental investigation of the terminal relaxation in high molecular weight polyisoprenes by dynamic mechanical measurements (C. A. Bero and C.M. Roland, Macromolecules, 29, 1562 (1996)) has found the terminal relaxation times to be more sensitive to changes in temperature for three-arm stars than for the linear polyisoprenes. Moreover, these measurements, carried out with significantly higher molecular weight samples than heretofore, show that the molecular weight dependence of the terminal relaxation times for three-arm star polyisoprenes is much weaker than the exponential dependence previously proposed (L. J. Fetters, et al., Macromolecules, 26, 647 (1993)). Tracer diffusion of labeled linear and three-arm star polyethylene-like diffusant molecules in a highly entangled linear polyethylene matrix exhibit temperature and molecular weight dependencies similar to those observed spectroscopically from bulk polymers. Both the temperature and molecular weight dependencies for the star-branched polymers are at variance with the predictions of the reptation model. It is shown here, however, that these observations can be reconciled through application of the coupling model of relaxation. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2503-2510, 1997
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  • 13
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2981-3000 
    ISSN: 0887-6266
    Keywords: sorption ; diffusion ; acetone ; poly(ethylene terephthalate) ; poly(ethylene 2,6-naphthalate) ; copolymers ; positron annihilation lifetime spectroscopy ; infrared spectroscopy ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Random copolymers of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalate) (PEN) were synthesized by melt condensation. In a series of thin, solvent cast films of varying PEN content, acetone diffusivity and solubility were determined at 35°C and an acetone pressure of 5.4 cm Hg. The kinetics of acetone sorption in the copolymer films are well described by a Fickian model. Both solubility and diffusivity decrease with increasing PEN content. The acetone diffusion coefficient decreases 93% from PET to PET/85PEN, a copolymer in which 85 weight percent of the dimethyl terephthalate in PET has been replace by dimethyl naphthalate 2,6-dicarboxylate. The acetone solubility coefficient in the amorphous regions of the polymer decreases by approximately a factor of two over the same composition range. The glass/rubber transition temperatures of these materials rise monotonically with increasing PEN content. Copolymers containing 20 to 80 wt % PEN are amorphous. Samples with 〈20% or 〉80% PEN contain measurable levels of crystallinity. Estimated fractional free volume in the amorphous regions of these samples is lower in the copolymers than in either of the homopolymers. Relative free volume as probed by positron annihilation lifetime spectroscopy (PALS) decreases systematically with increasing PEN content. Acetone diffusion coefficients correlate well with PALS results. Infrared spectroscopy suggests an increase in the fraction of ethylene glycol units in the trans conformation in the amorphous phase as the concentration of PEN in the copolymer increases. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2981-3000, 1998
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  • 14
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 3079-3086 
    ISSN: 0887-6266
    Keywords: diffusion ; block copolymer ; monomeric friction factor ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Monomeric friction factors, Ξ, for polystyrene (PS), polyisoprene (PI), and a polystyrene-polyisoprene (SI) diblock copolymer have been determined as a function of temperature in four poly(styrene-b-isoprene-b-styrene-b-isoprene) tetrablock copolymer matrices. The Rouse model has been used to calculate the friction factors from tracer diffusion coefficients measured by forced Rayleigh scattering. Within the experimental temperature range the tetrablock copolymers are disordered, allowing for measurement of the diffusion coefficient in matrices with average compositions determined by the tetrablock copolymers (23, 42, 60, and 80% styrene by volume). Remarkably, for a given matrix composition the styrene and isoprene friction factors are essentially equivalent. Furthermore, at a constant interval from the system glass transition temperature, Tg, all of the friction factors (obtained from homopolymer, diblock copolymer, and tetrablock copolymer dynamics) agree to within an order of magnitude. This is in marked contrast to results for miscible polymer blends, where the individual components generally have distinct composition dependences and magnitudes at constant T - Tg. The homopolymer friction factors in the tetrablock matrices were systematically slightly higher than those of the diblock, which in turn were slightly higher than those of the homopolymers in their respective melts, when all compared at constant T - Tg. This is attributed to the local spatial distribution of styrene and isoprene segments in the tetrablocks, which presents a nonuniform free energy surface to the tracer molecules. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3079-3086, 1998
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  • 15
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    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2703-2716 
    ISSN: 0887-6266
    Keywords: calorimetry ; dielectrics ; diffusion ; monoamine-triepoxide ; thermoset ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Calorimetry and dielectric relaxation spectroscopy during the growth of a polymer network in the stoichiometric mixture of a triepoxide with 4-chloroaniline have been performed in separate experiments to investigate the increase in the relaxation time with the number of covalent bonds. A comparison with the corresponding study of triepoxide-aniline and triepoxide-3-chloroaniline mixtures shows that steric hindrance of the amine group by chlorine slows the molecular dynamics and the relaxation time of the state containing a fixed number of bonds. The polymerization kinetics measured during ramp heating does not yield a reliable activation energy. A recent empirical relation between the relaxation time and the extent of polymerization, and the condition for the onset of diffusion-control kinetics have been examined using the data for these three polymerizing mixtures. The results show substantial deviations from the empirical relation and appear to conflict with our basic understanding of the polymerization process. It is shown mathematically that features attributed to the onset of diffusion-controlled kinetics can arise from thermochemical behavior alone, without reference to the molecular dynamics. An earlier theory for the change in the kinetics of an addition reaction from mass control to diffusion control has been considered, and is seen as relevant to the polymerization reactions. It is argued that the dielectric relaxation rate does not directly indicate the chemical reaction rate because the reorientational motion of the dipolar entities may not be coupled to the rotational and translational diffusion that brings the sterically hindered chemically reacting sites together. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2703-2716, 1998
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  • 16
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    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1471-1476 
    ISSN: 0887-6266
    Keywords: surfactant ; sodium dodecyl sulfate ; polyelectrolyte gel ; polyelectrolyte complexes ; poly(diallyldimethylammonium bromide) ; diffusion ; pyrene ; fluorescence ; fluorescent probe ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamics of the changing microenvironment of the fluorescent probe pyrene in slightly cross-linked networks of poly(diallyldimethylmmonium bromide) during diffusion of sodium dodecyl sulfate (SDS) in the gel phase has been investigated by fluorescence spectroscopy. Values of the spectral ratio I3/I1 for pyrene monomer included in SDS micelles in the swollen networks fall between the corresponding values for pyrene in water and for pyrene dissolved in SDS micelles in aqueous solution. In the narrow interval of the surfactant concentrations in the gel phase, the formation of pyrene excimers is observed. The values of the critical micelle concentration in the gel phase (ca. 5 × 10-4 to 8 × 10-4 mol/L) are tenfold lower than in aqueous solutions of the surfactant. The effective micellar diffusion coeffecient D in the gel phase increases with increasing swelling of the network. © 1993 John Wiley & Sons, Inc.
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  • 17
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    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2143-2150 
    ISSN: 0887-6266
    Keywords: chain rigidity ; diffusion ; polyimide ; hygroscopic stress ; solvent-induced swelling ; film ordering ; orientation ; activation energy ; bending beam technique ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The diffusion of NMP (n-methyl-pyrrolidinone) solvent in a semirigid rod-like PMDA-ODA (pyromellitic dianhydride-4,4′-oxydianiline) film coated on silicon is found to be case I diffusion at temperatures ranging from 30 to 90°C by the use of a bending beam technique. The diffusion constant increases for the 7.4 μm PMDA-ODA film (which was cured at 300°C) from 3.3 to 318 × 10-11 cm2/s as the diffusion temperature increases from 30 to 90°C. The corresponding hygroscopic stress in the direction parallel to the film decreases with the increase of temperature, possibly due to the softening of the film at elevated temperatures. The diffusion mechanism, however, changes from case II to case I in a rigid rod-like PMDA-PDA (pyromellitic dianhydride-p-phenylenediamine) film when the diffusion temperature increases. The change in the diffusion mechanism occurs at a higher temperature for thinner films, presumably due to higher ordering and/or orientation in the films. The activation energy for NMP diffusion in the PMDA-ODA films markedly decreases from 93 to 59 kJ/mole as the film thickness increases from 2.2 μm to 11.3 μm. This may also be attributed to decreased ordering in thicker films. © 1994 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 447-453 
    ISSN: 0887-6266
    Keywords: 13CO2 in polystyrene ; diffusion ; spin relaxation ; dual mode ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Recently we presented a dual-mode interpretation of the nuclear spin relaxation for 13CO2 sorbed in polycarbonate [E. J. Cain, W.-Y. Wen, A. A. Jones, P. T. Inglefield, B. J. Cauley, and J. T. Bendler, Journal of Polymer Science, Part B, Polymer Physics, Vol. 29, p. 1009 (1991)]. We have made similar investigation on spin relaxation for 13CO2 sorbed in polystyrene and are presenting the results in this report. 13C spin-lattice relaxation, spin-spin relaxation, and nuclear Overhauser enhancements (NOE) are reported for 13CO2 sorbed in glassy polystyrene. These spin relaxation parameters were determined as a function of temperature and Larmor frequency. A quantitative interpretation is based on a two-site, rapid exchange model, which is consistent with the NMR result. Gas molecules in the dissolved site have rotational, collisional, and translational dynamics typical of low molecular weight liquids. Sorbed molecules in the Langmuir site have much slower rotational and translational motions. The activation energy for motions in the dissolved site is about 7.5 KJ/mol, while that for the Langmuir site is about 15.5 KJ/mol. The translational diffusion constants derived from the NMR data range from 10-7 to 10-9 cm2/s and are consistent with the apparent diffusion constant from the permeability measurements of 4.9 × 10-8cm2/s at 35°C. A relation between the permeability value and the NMR values is available from a theoretical description of the dual-mode model in terms of a random walk on a lattice containing two sites. As a modification of our previous lattice model (E. J. Cain et al., Journal of Polymer Science, Part B, Polymer Physics, Vol. 29, p. 1009 (1991)), the temperature dependence of the fraction of Langmuir sites in the lattice is taken into account. Parameter values characterizing the motion of CO2 in polystyrene are found to be similar to the corresponding ones in polycarbonate. © 1993 John Wiley & Sons, Inc.
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  • 19
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    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 223-235 
    ISSN: 0887-6266
    Keywords: polyamide ; Nylon-66 ; microporous ; membrane ; ternary ; diffusion ; precipitation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An analysis is presented, which describes the isothermal ternary diffusion process encountered in the formation of the aliphatic polyamide membranes such as Nylon-66 by direct immersion-precipitation of a polymeric solution in a nonsolvent bath. A material coordinate is employed to derive the mass transfer equations for the membrane solution. The convective mass transfer in the coagulation bath is taken into account by solving the hydrodynamic boundary layer equations. Diffusion coefficients were measured and used to deduce ternary phenomenological coefficients. The computed results are found to agree with measured precipitation times and with membrane morphologies observed by scanning electron photomicrographs. © 1995 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1663-1671 
    ISSN: 0887-6266
    Keywords: sorption ; diffusion ; partial molar volume ; butanes ; butenes ; butylene ; butadiene ; 1,2-polybutadiene ; poly(ethylene-co-vinyl acetate) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Sorption and dilation isotherms and diffusion coefficients for seven hydrocarbons (n-butane, isobutane, 1-butene, cis-2-butene, trans-2-butene, isobutylene, and 1,3-butadiene) in two rubbery polymers, 1,2-polybutadiene (PB) and poly(ethylene-co-vinyl acetate) (EVAc), were measured at 25°C. Dissolution parameters (Henry's law coefficient and Flory-Huggins interaction parameter), partial molar volumes, and diffusion coefficients were determined. PB exhibited greater affinity and lower diffusivity than EVAc to the C4 gases, although the gases showed nearly the same partial molar volumes in the two polymers. The diffusivity of such elongated molecules as trans-2-butene in both polymers was higher than that of bulky molecules with similar partial molar volume, such as cis-2-butene and isobutylene. Pressure-dependent permeabilities of PB and EVAc films to the hydrocarbons were predicted and discussed based on the dissolution parameters and the diffusivities. © 1995 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 691-698 
    ISSN: 0887-6266
    Keywords: latex ; diffusion ; fluorescence ; healing ; sintering ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A steady-state fluorescence technique was used to examine the annealing of films formed from high-T latex particles above the glass transition temperature. The films were prepared by sintering pyrene-labeled poly(methyl methacrylate) latex particles. During the annealing processes, the transparency of the film changed considerably. Direct fluorescence emission from excited pyrene was monitored as a function of annealing temperature to detect these changes. Scanning electron microscopy in conjunction with Monte Carlo simulations of photon diffusion in latex film were used to interpret the fluorescence results. Healing temperature and time were measured at the point where the fluorescence emission intensity becomes maximum. This was associated with the longest optical path of a photon in latex film during healing of particle(SINGLEBOND)particle boundaries. Healing activation energy was measured and found to be 10 kcal/mol. © 1996 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 761-768 
    ISSN: 0887-6266
    Keywords: poly(ethylene terephthalate) ; poly(ethylene naphthalate) ; carbon dioxide ; diffusion ; glassy polymers ; modeling ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Finite difference modeling has been used to predict the results of gas transport experiments for a concentration-dependent diffusion coefficient. Experiments on the transport of CO2 in poly(ethylene terephthalate) and poly(ethylene naphthalate) had previously shown a difference between the effective diffusion coefficients for absorption and desorption runs of a double-sided experiment, but this effect had not been seen for single-sided experiments. The finite difference calculations show that such results are to be expected, and the parameters included in the models that attempt to describe the diffusion process in glassy polymers, such as the dual-mode model, and which lead to concentration-dependent diffusion coefficients, can be found by fitting the experimental data for the double-sided experiment using finite difference modeling. The dependence of the effective diffusion coefficient on pressure for the single-sided experiment can be correctly predicted using results from the double-sided experiment for an identical sample. © 1996 John Wiley & Sons, Inc.
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    Keywords: polymer blends ; crystallization ; diffusion ; composition inhomogeneities ; computer simulation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is well known that crystallization of one component in a polymer blend causes composition profiles around the growing spherulites. Amplitude and width of these profiles, respectively, depend on the ratio between the rates of diffusion and of spherulite growth. They can be determined by suitable experimental means. In the present article, the profiles are modeled, starting from Frank's solution of the diffusion equation in spherical coordinates under the boundary condition of moving walls that simultaneously are sources of the diffusing material. Modeled and experimentally determined profiles in PVDF/PEA and PCL/PS blends agree well. The analysis yields estimates for the diffusion coefficient D in polymeric melts as D ≅ (50··· 500) μm2/h. Finally, the interference of the composition profiles around several adjacent spherulites can be demonstrated. © 1996 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 769-780 
    ISSN: 0887-6266
    Keywords: poly(ethylene terephthalate) ; poly(ethylene naphthalate) ; carbon dioxide ; diffusion ; solubility ; permeability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Measurements have been made of the solubilities and effective diffusion coefficients at 25°C for carbon dioxide in random and uniaxially oriented samples of poly(ethylene terephthalate) and poly(ethylene naphthalate) (PET and PEN). Most measurements were made using a double-sided experiment in which the penetrant entered both sides of the sample simultaneously and the concentration was monitored as a function of time by means of infrared spectroscopy. Pressures of carbon dioxide from 0.125 to .5 atmospheres were employed. Finite difference modeling was used to determine concentration-dependent diffusion coefficients from the effective diffusion coefficients measured directly and to compare the results with the dual-mode and gas(SINGLEBOND)polymer matrix models. The results could be fitted slightly better by the dual-mode model than by the gas(SINGLEBOND)polymer matrix model, although the latter also provided a reasonable fit to the data. There was, however, no observed change in the spectrum of the absorbed carbon dioxide with concentration, as would be expected if it existed in two distinct states within the polymer, as required by the dual-mode model. No definite conclusion can thus be drawn about the applicability of the two models to the systems studied. © 1996 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1529-1539 
    ISSN: 0887-6266
    Keywords: polyurethane block copolymers ; water sorption ; diffusion ; dielectric relaxation spectroscopy ; plasticization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Equilibrium and dynamic sorption isotherm measurements, differential scanning calorimetry (DSC) measurements, and, mainly, dielectric relaxation spectroscopy (DRS) measurements by means of the thermally stimulated depolarization currents (TSDC) method were used to investigate the hydration properties of linear segmented polyurethane copolymers. Three types of samples were investigated with various fractions of hard and soft block segments. They were based on polyethylene adipate (PEA), 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO). At 20°C the water content h of the samples at various values of relative humidity rh increases in proportion to the weight fraction of soft block segments phase. At saturation (rh = 100%) the ratio of sorbed water molecules to polar carbonyl polyester groups is 0.13. At saturation at 20°C there is no fraction of freezable water. The glass transition temperature, Tg, measured by DSC and by TSDC, shifts to lower temperature with increasing h by about 8-10 K at saturation at 20°C. A dielectric relaxation mechanism related to interfacial polarization in the phase-separated morphology is also plasticized by water in a way similar to that observed for the main (α) relaxation. © 1996 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2027-2033 
    ISSN: 0887-6266
    Keywords: Sorption ; dilation ; diffusion ; penetrant-induced isothermal glass transition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of a penetrant-induced isothermal glass transition on sorption, dilation, and diffusion behavior was studied in a single experimental run for CO2 in cast polybenzylmethacrylate films. The dual-mode type sorption isotherms below the glass transition temperature of the polymer changed to linear ones above a certain concentration. Meanwhile, partial molar volume of CO2 determined from the dilation of the films above the concentration gave a value very close to the one reported for rubbery polymers, and diffusion coefficients became less concentration-dependent. The results were conformable to the concept of unrelaxed volume in glassy polymers. © 1996 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 725-734 
    ISSN: 0887-6266
    Keywords: swelling ; sorption ; diffusion ; natural rubber ; interaction parameter ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The sorption and transport of four aliphatic hydrocarbons into natural rubber crosslinked by different vulcanization systems [conventional (CV), efficient (EV), peroxide (DCP) and a mixed system consisting of sulfur and peroxide (mixed)] were investigated in the temperature interval of 28-60°C. Of the four systems, natural rubber vulcanized by DCP exhibited lowest penetrant uptake. It was observed that the kinetics of liquid sorption in every case deviates from the regular Fickian trend, characteristic of sorption of liquids by rubbers. The diffusion coefficient, activation energy of sorption, enthalpy, entropy, and the rubber-solvent interaction parameter were evaluated for the four systems from the swelling data. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 725-734, 1997
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    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1043-1048 
    ISSN: 0887-6266
    Keywords: diffusion ; gold, silver ; polycarbonate ; glassy state ; free-volume theory ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Diffusion coefficients between 5 × 10-14 and 1 × 10-16 cm2 s-1 have been measured for diffusion of gold and silver in the glassy state of bisphenol trimethylcyclohexanen polycarbonate in the temperature range between Tg = 507 K and 420 K using the radiotracer technique in combination with ion-beam sputtering for serial sectioning. The Arrhenius plot exhibits a downward curvature, which is interpreted within an extension of the free-volume theory to the glassy state by Vrentas and Duda. The very small metal diffusivities in comparison to values for gas molecules of comparable size suggest substantial interaction energies. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35:1043-1048, 1997
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 567-572 
    ISSN: 0887-6266
    Keywords: surface ; interfaces ; diffusion ; polystyrene ; polyphenylene oxide ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Symmetric polydisperse (Mw = 23 × 104, Mw/Mn = 2.84) and monodisperse (Mw = 21 × 104, Mw/Mn 〈 1.05) polystyrene (PS), and asymmetric polydisperse PS/poly(2,6-dimethyl 1,4-phenylene oxide) (PPO) interfaces have been bonded in the vicinity of the glass transition temperature (Tg) of PS. In a lap-shear joint geometry, strength develops in all cases with time to the fourth power, which indicates that it is diffusion controlled. Strength developing at short times at the polydisperse PS/PS interface, at 90°C, is higher than that at the monodisperse interface, at 92°C (at Tg - 13°C in both cases), presumably due to the contribution of the low molecular weight species. The decrease of strength at the PS/PPO interface when the bonding temperature decreases from 113 to 70°C, i.e., from Tg + 10°C to Tg - 33°C of the bulk PS, indicates a high molecular mobility at the surface as compared to that in the bulk, and can be expressed by a classical diffusion equation, which is valid above Tg (of the surface layer). © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 567-572, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 373-381 
    ISSN: 0887-6266
    Keywords: pressure-sensitive adhesive ; PSA ; tackifier ; tack adhesion ; polyisoprene ; poly(ethylene-propylene) ; pulsed gradient spin echo-nuclear magnetic resonance ; PGSE-NMR ; diffusion ; n-butyl ester of abietic acid ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A detailed study of the mobility of a tackifying resin in a pressure-sensitive adhesive (PSA) has been done for the first time. The objective of this work is to relate changes in adhesive performance with tackifier loading to tackifier mobility. Tackifiers are low-molecular weight resins that improve the overall performance of PSAs. They increase the adhesive tack or the ability to form a bond of measurable strength after brief contact under slight applied pressure. In this study the diffusion of n-butyl ester of abietic acid (n-BEAA) in either polyisoprene (PI) (Mw = 195,000 Mw/Mn ∼ 1.05) or poly(ethylene-propylene) (PEP) (Mw = 40,000 Mw/Mn ∼ 2.30) was measured by Pulsed Gradient Spin Echo-Nuclear Magnetic Resonance (PGSE-NMR) as a function of both tackifier concentration and temperature. The concentration dependence of the tackifier's diffusion coefficient was weak for both systems. The weak variation in mobility with composition for the PI/n-BEAA system was consistent with that system's weak variation in tack with composition. On the other hand, blends of PEP/n-BEAA showed only modest variation in mobility, even though these adhesive systems showed appreciable enhancement of tack at intermediate compositions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 373-381, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2771-2780 
    ISSN: 0887-6266
    Keywords: drying ; semicrystalline polymers ; poly(vinyl alcohol) ; solvent removal ; modeling ; diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The drying mechanism of semicrystalline poly(vinyl alcohol) (PVA) was investigated. PVA samples of various molecular weights were crystallized by annealing at temperatures slightly above the glass transition temperature of PVA, and swollen in water for different time periods. The water volume fraction in the sample was measured using a buoyancy technique. The samples were dried in air at constant temperatures, and the drying kinetics were investigated using thermogravimetric analysis. The change in degree of crystallinity of the swollen polymer during drying was measured by differential scanning calorimetry (DSC) as well as by Fourier transform infrared spectroscopy (FTIR). The degree of crystallinity of the samples increased during drying, which in turn was found to alter the drying rate. The drying kinetics were faster at higher temperatures, for lower molecular weights, and for lower degrees of crystallinity. A mathematical model was developed to predict drying rates of semicrystalline polymers by considering the crystallization kinetics during drying. The model predictions included the thickness of the polymer sample, the degree of crystallinity of the polymer, and the water weight loss as functions of drying time. Model predictions were found to agree reasonably well with the experimental results. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2771-2780, 1998
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    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 585-589 
    ISSN: 0887-6266
    Keywords: interpolymer ; membranes ; diffusion ; percolation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1413-1425 
    ISSN: 0887-6266
    Keywords: membrane ; immersion ; precipitation ; cellulose acetate ; ternary ; diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An analysis is presented, which describes the isothermal ternary diffusion process encountered in the formation of a cellulose acetate polymeric membrane by a direct immersion-precipitation of polymeric solutions in a nonsolvent bath. A material coordinate was employed to derive the mass transfer equations for the membrane solution and the convective mass transfer in the coagulation bath was taken into account by solving the hydrodynamic boundary layer equations. Diffusion coefficients were measured and used to deduce ternary phenomenological coefficients. The computed results are found to agree with the experimental precipitation time and membrane morphologies observed in scanning electron photomicrographs. © 1994 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1505-1514 
    ISSN: 0887-6266
    Keywords: polyisobutylene ; toluene ; pulsed field gradient nuclear magnetic resonance ; diffusion ; Vrentas-Duda Theory ; Fujita theory ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The self-diffusion coefficients of toluene in polyisobutylene have been analyzed using the Vrentas-Duda free volume diffusion model. The diffusion coefficients were determined at different temperatures and concentrations, using the pulsed field gradient nuclear magnetic resonance technique. The data were satisfactorily described by the model and the size of the polymer jumping unit was extracted. Comparisons were made with the Fujita free volume theory and the Fujita free volume parameters were extracted from the Vrentas-Duda free volume parameters. From the diffusion data that now available, it can be concluded that for most polymers the jumping unit is about 1.5 times the polymer monomer molecular weight. The activation energy of the toluene diffusion in polyisobutylene is compared with the activation energies of other penetrants in the same polymer. The diffusion data presented in this work show that the energy per mole required to overcome the attractive forces which constrain a diffusing species to its neighbors should be considered to be zero, in order to be able to extract the free volume parameters (from viscosity and diffusion data) with an acceptable uncertainty. ©1995 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1889-1898 
    ISSN: 0887-6266
    Keywords: diffusion ; glassy polymers ; dual mode transport theory ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymer matrix, divided in a number of cells in which the penetrant molecules can be sorbed and migrate, is considered. Each cell has been assigned an effective energy value that obeys a particular distribution. The effective diffusion coefficient and its concentration and temperature dependence are determined. The origin of sorbed penetrant mobility is studied. Using a delta-Dirac distribution for the site's energetic values, the model is reduced in the appropriate limit (low pressure) to other formulations of the dual transport model. More general results, allowing the site's energetic values to be drawn from a Gaussian distribution, are also given. © 1994 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1927-1941 
    ISSN: 0887-6266
    Keywords: copolymer ; diffusion ; light scattering ; polymer-polymer interactions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solution properties for random and diblock copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA) have been measured by dynamic and total intensity light scattering in solvents of differing quality. The results are compared with the corresponding properties for PS and PMMA homopolymers of similar molecular weight, in order to determine if interactions between unlike monomers are significant. The hydrodynamic radius (Rh) and diffusion second virial coefficient (kd) for the random copolymer are found to be larger than the corresponding values for the homopolymers in a solvent which is near-theta for the two homopolymers, whereas no such effect is observed for the block copolymer. This suggests that most intrachain interactions occur a relatively short distance along the chain backbone. In a mutual good solvent Rh and kd of the random copolymer are comparable to the average of the values for the homopolymers, indicating that in a good solvent monomer/solvent interactions dominate over monomer/monomer interactions. For an isolated diblock copolymer in a mutual good solvent, there is no evidence that interactions between unlike monomers lead to additional expansion of the entire molecule, as measured by Rh, nor expansion of the individual blocks as probed by light scattering with one block optically masked. However, at low but finite concentration there is evidence (the coefficients of the binary interaction terms in the viscosity and the mutual diffusion coefficient, and the second and third virial coefficients) that a weak ordering effect may exist in block copolymer solutions, far from the conditions where microphase separation occurs. Finally, measurements of ternary polymer-polymer-solvent solutions show no dependence on monomer composition or monomer distribution for the tracer diffusion of probe PS-PMMA copolymers in a PMMA/toluene matrix. This indicate that the frictional interaction is largely unaffected by interactions between unlike monomers. However, there is evidence that the thermodynamic interaction is more unfavorable between a random copolymer and the homopolymer matrix than between a diblock and the matrix. © 1994 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2153-2160 
    ISSN: 0887-6266
    Keywords: membrane ; diffusion ; dual-mode sorption ; permeation ; infrared spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectra of CO2 sorbed in rubbery and glassy polymeric membranes were measured to examine the relationships between the spectroscopic data and the physical properties of the membranes. The two peaks observed in the spectra of CO2 were attributed to the R branch and P branch of CO2 sorbed in the membranes based on the consideration that both peaks were observed at a temperature above the glass transition temperature of the membranes. Apparent diffusion coefficients of CO2 in the membranes were measured from the desorption kinetics of CO2 detected by FTIR spectroscopy. The solubility coefficients of CO2 were also estimated from absorbance spectra of CO2 sorbed in the membranes using Lambert-Beer's rule. The permeability, solubility, and diffusion coefficients estimated by the FTIR method were found to correlate well with the coefficients obtained by conventional methods such as vacuum-pressure or sorption isotherm methods. © 1996 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2161-2166 
    ISSN: 0887-6266
    Keywords: triblock copolymer ; mixtures ; RPA ; neutron scattering ; dynamic relaxation ; diffusion ; rouse modes ; reptation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Static and dynamic scattering properties of polymer blends and block copolymers are examined within the random phase approximation (RPA). A self-consistent theoretical scheme for a simultaneous analysis of elastic and quasielastic scattering data is presented. The case of a triblock copolymer made of an ordinary central block and two deuterated lateral blocks in a matrix of deuterated homopolymers is considered in detail. The theoretical predictions of the RPA are compared with the experimental data obtained by elastic neutron scattering experiments using mixtures of deuterated poly(dimethylsiloxane) homopolymers and copolymers made of three blocks of approximately equal sizes. The lateral blocks are deuterated poly(dimethylsiloxane) and the central one is an ordinary poly(dimethylsiloxane). A good agreement is found in the whole range of wavevectors covered by the experiments. An extension of the RPA to the analysis of the dynamical scattering data for the same systems is put forward. It is shown how the time relaxations of the bare response functions obtained from the single chain dynamics are used to extract the intermediate scattering function characterizing the system of interacting chains. © 1996 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2083-2091 
    ISSN: 0887-6266
    Keywords: nuclear reaction analysis ; copolymer blends ; diffusion ; poly(arylether sulfone)s ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The interdiffusion and miscibility behavior of three different types of modified poly(arylether sulfone)s with deuterated poly(arylether sulfone) is studied by depth profiling using the nuclear reaction D(3He, α)p. The diffusion coefficients are found to be in the range of 10-15 and 10-14 cm2/s at 195°C. A random copolymer of poly(arylether sulfone) containing 4,4-bis-(4′-hydroxyphenyl)valeric acid units is only partially miscible with deuterated poly(arylether sulfone) when the comonomer content is 8.8 mol %, whereas blends with comonomer contents of 1.7 and 4.5 mol % are miscible as indicated by complete interdiffusion. The transition from miscibility to immiscibility is caused by repulsive interactions of copolymer segments and can be explained in terms of a mean-field theory of random copolymer blends. Also, poly(arylether sulfone)s grafted with 0.4 wt % maleic anhydride or having pyromellitic anhydride endgroups are miscible with deuterated poly(arylether sulfone)s. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2083-2091, 1997
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    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2397-2408 
    ISSN: 0887-6266
    Keywords: diffusion ; glassy polymers ; small molecules ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Small molecules in glassy polymers are considered to occupy sites with a distribution of free energies of dissolution. Then their diffusivity depends on concentration and temperature in the same way as it has been derived for hydrogen atoms in metallic glasses. For hydrogen it was shown that the tracer diffusion coefficient is proportional to the activity coefficient of the solute atoms. The latter can be evaluated from measured data of sorption of the small molecules in the polymer. Knowing this quantity, the thermodynamic factor can be calculated and the concentration dependence of the mutual diffusion coefficient is obtained in excellent agreement with published experimental results. New experimental results are presented for the diffusion coefficient of CO2 in Kapton and four polycarbonates (BPA-PC, BPZ-PC, TMBPA-PC, and TMC-PC) in the low CO2 pressure range of a few mbar up to 1 bar. The results are in agreement with the model developed for hydrogen. The reference diffusion coefficient, which is a fitting parameter of the model that is independent of the distribution of free energies is smallest for the polycarbonate BPZ-PC having a high γ-relaxation temperature. This correlation between the diffusion coefficient and the dynamics of the polymer can be found for other substituted polycarbonates as well. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2397-2408, 1997
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2211-2224 
    ISSN: 0887-6266
    Keywords: starch ; mechanical properties ; percolation ; clustering ; diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The use of starch microcrystals as biodegradable particulate filler is evaluated by processing composite materials with a weight fraction of starch ranging from 0 to 60%. In a previous work [Macromolecules, 29, 7624] the preparation technique of a colloidal suspension of hydrolyzed starch and the processing of composite materials by freeze drying and molding a mixture of aqueous suspensions of starch microcrystals and synthetic polymer matrix were presented. Starch microcrystals with dimensions of a few nanometers were obtained from potatoes' starch granules, and it was found that this filler produces a great reinforcing effect, especially at a temperature higher than Tg of the synthetic matrix. Classical models for polymers containing nearly spherical particles based on a mean field approach could not explain this reinforcing effect. The morphology of these nanocomposite systems is discussed in light of aggregate formation and percolation concepts. The sorption behavior of these materials is also performed. Starch is a hygroscopic material, and it is found that the composites absorb more water, as the starch content is higher. The diffusion coefficient of the penetrant is predicted from modified mechanical three branch series-parallel model based on a percolation approach. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2211-2224, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1695-1702 
    ISSN: 0887-6266
    Keywords: sorption ; dilation ; diffusion ; conditioning effect ; glassy polymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Sorption, dilation, and diffusion behaviors were studied for the system of polysulfone/CO2 with regard to the effects of CO2 conditioning, i.e., exposure to high-pressure CO2. Concurrent measurements of solubility, dilation, and diffusivity were performed for polysulfone films before and after the conditioning at 25 and 50 atm. While the solubility and dilation were enhanced by the conditioning, the diffusivity appeared to be depressed. Results were analyzed on the basis of the dual-mode sorption model, with the assumption that the Henry's law dissolution was not affected by the conditioning. Consistent description was achieved then by attributing the changes to increased amount of Langmuir adsorption. The conditioning effect on the diffusivity, which had not been reported before based on CO2 sorption kinetics, suggests that the permeability of glassy polymers would not always be enhanced by the conditioning, but may also be decreased. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1695-1702, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1713-1719 
    ISSN: 0887-6266
    Keywords: polymer ; diffusion ; free-volume theory ; inverse gas chromatography ; gravimetric sorption ; ethylene-propylene-diene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Self-diffusion and partition coefficients were measured for two commercial ethylene-propylene-diene copolymers (EPDM) and five solvents at infinite dilution using inverse gas chromatography. Mutual diffusion coefficients for solvents in EPDM also were measured for finite concentration using gravimetric sorption for three of the solvents. From the inverse gas chromatography experimental values for self-diffusion coefficients were obtained. Free-volume parameters were obtained through regression of the self-diffusion coefficient as a function of temperature. Mutual diffusion coefficients as a function of concentration were predicted using free volume theory and compared with experimental data obtained using gravimetric sorption. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1713-1719, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2435-2447 
    ISSN: 0887-6266
    Keywords: poly(vinylidene fluoride) ; carbon dioxide ; supercritical fluid ; diffusion ; partial molar volume ; solubility parameter ; mass sorption ; high pressure ; dilation ; Sanchez-Lacombe model ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The article reports on the behaviour of poly(vinylidene fluoride) in carbon dioxide at 42°C and 80°C and in a pressure range of 0.1-30 MPa. Experimental techniques for the measurement of gas mass uptake and polymer dilatation are described and the corresponding data are reported as mass sorption and dilatation isotherms, respectively. The mass uptake experiment was also used to follow the evolution of the coefficient of diffusion of carbon dioxide into the polymer as a function of pressure or concentration. An analysis for the calculation of the partial molar volume of carbon dioxide as a function of pressure is also given, which shows that the ‘apparent’ partial molar volume of the carbon dioxide decreases with pressure to very low values, at high pressure. The computed values are significantly less than those for either the liquid or the solid phases of pure carbon dioxide, and also lower than some data previously reported for silicone elastomers. A consideration of the origins of this apparent anomaly is given in the conclusions. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2435-2447, 1998
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    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 743-757 
    ISSN: 0887-6266
    Keywords: gas transport ; drawn polyethylene ; orientation ; diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study has been made of the gas transport properties of polyethylene films of two different grades, Hizex 7000F and Rigidex 002-55, one-way drawn at 115°C to draw ratios in the range 1-20. Measurements of the permeability and diffusion coefficients of helium, oxygen, carbon dioxide and nitrogen have been made with a dynamic flow rate technique, utilizing a mass spectrometer detection system, and of oxygen using a commercial OXTRAN system. The samples were characterized by the measurement of density, birefringence and modulus and by wide-angle x-ray diffraction and differential scanning calorimetry. There is a large decrease in both the permeability and diffusion coefficients for all gases with increasing polymer draw ratio, with up to an 80-fold decrease in permeability for the larger permeants compared with the 10-fold decrease observed for helium. The solubilities of all the gases decrease only by a factor of ∼ 2. The diffusion results are discussed in terms of geometric impedance and chain immobilization factors. The solubilities, on the other hand, appear to relate primarily to the amorphous volume fraction of the polymer. © 1993 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1503-1518 
    ISSN: 0887-6266
    Keywords: anomalous transport ; glassy polymers ; diffusion ; Deborah number ; Case II transport ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A mathematical model was developed to explain the anomalous penetrant diffusion behavior in glassy polymers. The model equations were derived by using the linear irreversible thermodynamics theory and the kinematic relations in continuum mechanics, showing the coupling between the polymer mechanical behavior and penetrant transport. The Maxwell model was used as the stress-strain constitutive equation, from which the polymer relaxation time was defined. An integral sorption Deborah number was proposed as the ratio of the characteristic relaxation time in the glassy region to the characteristic diffusion time in the swollen region. With this definition, an integral sorption process was characterized by a single Deborah number and the controlling mechanism was identified in terms of the value of the Deborah number. The model equations were two coupled nonlinear differential equations. A finite difference method was developed for solving the model equations. Numerical simulation of integral sorption of penetrants in glassy polymers was performed. The simulation results show that (1) the present model can predict Case II transport behavior as well as the transition from Case II to Fickian diffusion and (2) the integral sorption Deborah number is a major parameter affecting the transition. © 1993 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 993-999 
    ISSN: 0887-6266
    Keywords: deformation ; polycarbonate ; diffusion ; strain-enhanced diffusion ; free volume ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Measurements of the emission of purposely entrained volatiles (Ar and D2O) during the loading and unloading of a bisphenol-A polycarbonate in vacuum are made by quadrupole mass spectrometry. Transient loading events are accompanied by dramatic increases in emission, reflecting a similar rise in the diffusion constant of the measured species. We attribute this change to an increase in size of molecular voids in the polymer network, which accompany the increase in sample volume under load. The results are interpreted in terms of the Dolittle relation in which the diffusion constant depends exponentially upon v*/vf0, the ratio between an activation volume for diffusion and the average size of the relevant voids in the polymer network. Our data suggests that v*/vf0 is unusually low in the D2O-polycarbonate system, which we attribute to a relatively large value of vf0; this would be consistent with the relatively long distance between flexible links in the polycarbonate structure. © 1994 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 501-504 
    ISSN: 0887-6266
    Keywords: free volume ; diffusion ; gas transport ; dilation ; Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
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    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 545-555 
    ISSN: 0887-6266
    Keywords: polyimides ; dielectric relaxation ; dipole moments ; water sorption ; diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of structure on the sorption kinetics of water and of various organic solutes into polyimide (PMDA-ODA) thin films was studied. The major techniques employed include measurements of sorption kinetics, density, and dielectric relaxation. More solute uptake, lower densities and higher diffusivities were observed for films cured at lower temperatures. By measuring both changes of mass and of density, the volume expansion of the polymer due to each solute was obtained; this was found to be proportional to the molar volume of the solute. The two dielectric relaxation peaks (denoted by γ1 and γ2) due to water (and other solutes) were studied in detail to obtain the relevant activation energies and the separate dipole moments. While water and methylene chloride appear in both γ1 and γ2 configurations, methyl and ethyl alcohol appear mainly as γ2, while acetic acid is primarily γ1. It was concluded that the γ1 configurations are relatively homogeneously distributed throughout the polymer, involving loose bonding to the polymer structure, while the γ2 configurations involve small clusters, probably chains of molecules. © 1993 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 341-352 
    ISSN: 0887-6266
    Keywords: polyurethane cationomer ; oxygen permeation ; diffusion ; emulsion ; solution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic oxygen permeation measurements at 20-70°C on films cast from solutions and emulsions of three series of polyurethane (PU) cationomers based on MDI, HDI, and TDI that are the subject of Parts I and II of this series were made by Barrer's vacuum technique. For the MDI system, films cast from solutions of ionized PU exhibit permeation coefficients P that are higher at 20-40°C (below the glass transition temperature Tgh of the hard domains) than at 50-70°C (above Tgh) by factors of about 5 and 40. This is the opposite of what is observed for normal homopolymers and un-ionized PU. This phenomenon is attributed to the continuous/dispersed morphology of these films. At the low temperature, oxygen molecules diffuse through the continuous phase (soft domains) only. But at the high temperature, oxygen molecules diffuse through soft domains and subsequently through hard domains, leading to an increase in diffusion pathlength. For films cast from the PU emulsions, such a drop in P was not observed because the hard domains were partially inverted from the dispersed phase to a continuous phase that gives an interwoven morphology. Such morphology allows oxygen molecules to diffuse through soft and phase-inverted hard domains simultaneously. For the HDI and TDI systems, P and D vs. 1/T plots show no zone of discontinuity. This is attributed to a Tgh that is lower than or close to the permeation temperature. © 1995 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1269-1280 
    ISSN: 0887-6266
    Keywords: ionomer ; permeation ; diffusion ; sorption ; gas ; Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Transport properties of several gases in two ethylene-acrylic acid ionomers characterized by a different amount of acrylic acid groups and percentage of neutralization have been investigated. Sorption and permeation experiments have been performed with N2, O2, CO2, CH4, C2 H6, and SF6 in the 25-65°C range and with C3H8 only at 25°C. Gas permeabilities, diffusivities, and solubilities were evaluated along with activation energies and heats of solution. Data obtained in the present investigation were compared to analogous results reported in literature for polyethylene to better highlight the effect of ionic aggregates on the gas transport mechanism. © 1995 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1621-1626 
    ISSN: 0887-6266
    Keywords: poly(p-phenylene benzobisoxazole) ; PBO ; polyphosphoric acid ; diffusion ; fluorescence microscopy ; aqueous coagulants ; nonaqueous coagulants ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Diffusion of aqueous and nonaqueous coagulants into lyotropic/nematic solutions of poly(phenylene benzobisoxazole) in polyphosphoric acid using fluorescence microscopy is reported. The fluorescence microscopy technique offers advantages in that the experiment is independent of the coagulant and the experiments can be performed in a front surface mode so that optically thin samples are not required. The diffusion process is modeled as Case II diffusion as described by Crank and Park. The apparent diffusion coefficients are found to range from ∼ 2 × 10-6 cm2/s to ∼ 2 × 10-7 cm2/s for aqueous and nonaqueous coagulants. The apparent diffusion coefficients can be varied by several orders of magnitude (e.g., down to ∼ 3 × 10-10 cm2/s) by varying the concentration of polyphosphoric acid in the coagulant. © 1995 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1495-1503 
    ISSN: 0887-6266
    Keywords: polyisobutylene ; toluene ; pulsed field gradient nuclear magnetic resonance ; diffusion ; fujita free volume theory ; Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology , Physics
    Notes: The self-diffusion coefficients of toluene in polyisobutylene (PIB) solutions were determined using the pulsed field gradient nuclear magnetic resonance technique. The volume fraction of toluene in the polymer was varied from 0.045 up to 0.712 and the temperature was varied from 225 K up to 368 K. The concentration dependence of the data was interpreted using the Fujita free volume theory and the temperature dependence was interpreted with the WLF equation. These models describe separately the concentration and temperature dependencies of the toluene self-diffusion coefficients very well and the resulting free volume parameters are in good agreement with the ones extracted from the analysis of viscosity data on the same system. ©1995 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 2343-2349 
    ISSN: 0887-6266
    Keywords: diffusion ; sorption ; fluorescence monitoring ; polymer coatings ; water ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The fluorescent molecular rotor probes 4-tricyanovinyl-[N-(2-hydroxyethyl)-N-ethyl]-aniline, tricyano-4-(dimethylamino) benzylidene, and tricyanovinyljulolidene have been used as extrinsic fluorescence probes for quantitative monitoring of water uptake in polymeric coatings. The presence of water causes plasticization of the polymer, which results in increased local mobility within the film. The nonradiative decay pathways of the rotor probes are increased as local mobility increases, and the resulting decrease in fluorescence intensity of the probes is directly proportional to the amount of water sorbed. Beyond allowing for the characterization of sorbent content, this fluorescence technique can be used to determine the diffusion coefficient of water in a polymer film. The relative change in fluorescence fits well to a Fickian diffusion model, yielding a diffusion coefficient for water of 3 × 10-8 cm2/s in poly(vinyl acetate), and a value of 6 × 10-9 cm2/s in a room-temperature cured epoxypolyamide, in excellent agreement with diffusion coefficient values determined from gravimetric analysis. Preliminary studies also demonstrate the utility of molecular rotor probes to monitor water uptake in individual layers of multilayered polymer systems. © 1995 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2899-2909 
    ISSN: 0887-6266
    Keywords: block copolymer ; diffusion ; forced Rayleigh scattering ; monomeric friction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Forced Rayleigh scattering (FRS) has been used to measure the self-diffusion coefficient, D, of a lamellar-forming polystyrene-polyisoprene diblock copolymer (MPS = 1.0 X 104, MPI = 1.3 X 104) as a function of temperature. The measurements traverse the order-disorder transition (ODT), which occurs at 160°C. There is no obvious change in either D or the temperature dependence of D at the ODT, in agreement with measurements on several other systems. Electron microscopy confirms that the sample in the ordered state is quenched, with no long-range orientation of lamellae, and a typical grain size well below 1 μm. In contrast to previous measurements on a similar styrene-isoprene diblock, these FRS signals are well-described by single exponential decays; this may be largely attributed to differences in average grain size. The temperature dependence of D is modeled with several empirical expressions, based on the known monomeric friction factors for pure polystyrene and pure polyisoprene, but without quantitative success. These results underscore the need for a greater understanding of the composition and temperature dependences of local friction in polymer mixtures. © 1996 John Wiley & Sons, Inc.
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    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 569-585 
    ISSN: 0887-6266
    Keywords: phase inversion ; diffusion ; in situ dynamics ; membrane morphology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The diffusion and gelation dynamics of nonsolvent-induced phase inversion in several polyethersulfone (PES)/solvent/nonsolvent systems are observed using a dark-ground optical technique. The observed dynamics are correlated with the resultant morphologies of the solidified gels obtained via scanning electron microscopy. In situ dynamic measurements show that rapid precipitations result in finger formation and delayed precipitations result in sponge formation. Rapid precipitations for some systems also exhibit an initial region of high, anomalous diffusion front motion which correlates well with the appearance of finger-like macrovoids in the film sublayer. Micrographs of both thin (200-300 μm) and thick (3 mm) films formed by liquid-liquid demixing clearly show that the overall morphologies scale with initial film thickness. However, as observed for the cellulose acetate (CA)/dimethylsulfoxide (DMSO)/H2O system, the possibility of crystallization can complicate the scaling analysis. A ternary diffusion model is also employed to describe the isothermal diffusion encountered during the formation of PES membranes. Binary thermodynamic and kinetic parameters needed for computations are determined from experimental data. Model results agree well with experimental observations. The model accurately predicts the transition from finger-to-sponge formation, as well as other observed trends in dynamics and morphology. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 569-585, 1997
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 337-344 
    ISSN: 0887-6266
    Keywords: infrared spectroscopy ; multicomponent ; diffusion ; polymer ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this study, diffusion coefficients of toluene/methyl ethyl ketone (MEK) mixtures in polyisobutylene were measured at 50°C using vapor sorption FTIR-ATR (Fourier Transform Infrared Attenuated Total Reflectance) spectroscopy. For three mixture compositions, the diffusion coefficients were determined using a diffusion framework for ternary systems. The “crossterm” diffusion coefficient for MEK was found to be very small under the experimental conditions studied here, while that for toluene was found to increase with increasing MEK concentration. On the basis of this finding, a binary diffusion model was used to determine diffusion coefficients for MEK over a wide range of mixture compositions and the results compared well with those determined from pure MEK transport data. Relative transport rates during integral sorption experiments with mixtures were used to explain the results. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 337-344, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2635-2642 
    ISSN: 0887-6266
    Keywords: polypyrrole film ; bending ; strain ; sorption isotherm ; diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The sorption-induced bending and recovery motion of PPy films containing different dopant ions have been investigated, and the interaction between water vapor and PPy was studied from sorption isotherms and kinetics. It was found that the PPy/BF4 film exhibited the most rapid motion, and the initial speeds of bending and recovery motion were 7.9 and 5.9 mm s-1, respectively. The linear expansion coefficient of the film increased in order of PPy/DBS, PPy/TsO, PPy/ClO4, and PPy/BF4, which is consistent with the packing density of the PPy chains (φPPy). The dual-mode sorption model applied to the isothermal sorption of water vapor to the PPy demonstrated that the Langmuir's capacity constant increased in the same order with the φPPy, while the Henry's law constant was nearly constant. The sorption kinetics obeyed Fickian despite the dimensional change of the films, and the PPy/BF4 film had the largest diffusion coefficient of 3.13 × 10-8 cm2 s-1. The experimental results indicated that the kind of dopant ion was crucial to the thermodynamics and kinetics of sorption, and the quick and intensive bending motion of PPy/BF4 films was attributed to the fast diffusion of water vapor, which caused the large dimensional change of the film.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2635-2642, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2237-2246 
    ISSN: 0887-6266
    Keywords: polypyrrole film ; bending ; water vapor sorption ; diffusion ; anisotropic expansion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polypyrrole films containing perchlorate were electrochemically synthesized and the bending and recovery motion of the films obtained has been investigated. It was found that the thickness of the film and ambient relative humidity (RH) were crucial to the motion of film: An increase of the film thickness decreased the displacement of the bending but increased the bending stress. On the other hand, an increase of the ambient RH decreased both functions. The motion of film was caused by the difference of expansion on both sides of the film owing to anisotropic sorption of water vapor, which could be expressed by the diffusion-limited bending model. The diffusion coefficients calculated from the bending and recovery motion at 25°C, RH 50% were 12.2 × 10-8 cm2 s-1 and 3.5 × 10-8 cm2 s-1, respectively. The maximum expansion of the film surface calculated from the bending curve was about 0.36%. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2237-2246, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2923-2930 
    ISSN: 0887-6266
    Keywords: polymer blends ; crystallization ; diffusion ; composition inhomogeneities ; internal spherulite structure ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Composition profiles develop around growing PVDF spherulites in a blend with PMMA. These profiles assume stationary courses after a certain crystallization time provided that the overall degree of crystallinity is not too high. The composition-dependent growth rate and the diffusion-controlled remove of the surplus PMMA from the spherulite surface are then in a stationary equilibrium. The internal structure of the spherulites will then be homogeneous, too. Upon isothermal crystallization of a PVDF/PMMA = 60/40 (wt %) blend at 160°C for at least 4 h, the spherulites internal degree of crystallinity xc as related to the PVDF fraction obeys the inequality 55 wt % ≤ xc ≤ 84 wt %. The overall PMMA content within the spherulites as averaged over its whole inside has been determined by IR microscopy. It amounts to about 15 wt %. In contrast, the PMMA content of the amorphous phase within the spherulites (averaged again over its whole inside) ranges between 28 and 52 wt %. This composition jumps at the spherulite surface to 52 wt %. From the slope of the composition profiles outside the spherulites that have a width of more than 50 μm, the effective chain diffusion coefficient in blends as averaged over both components can be calculated to amount to (250 ± 100) μm2h-1. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2923-2930, 1998
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    Polymer International 39 (1996), S. 251-260 
    ISSN: 0959-8103
    Keywords: water ; ethanol ; crystallinity ; concentration-dependence ; diffusion ; poly(vinylalcohol) membranes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Solvent sorption and diffusion are the key processes that control membrane performances in membrane processes. The sorption characteristic of water and ethanol vapours in poly(vinylalcohol) (PVA) membranes of different crystallinity degrees was measured by microgravimetry and the diffusion characteristic was calculated from the sorption kinetics at different water activities by curve fitting. The sorption isotherms for water vapour in membranes of 28, 37, 44 and 56% crystallinity degrees at 40°C obey the Flory equation based on the polymer lattice model. When the sorption extent was corrected by assuming that only the polymer amorphous phase is accessible to the penetrant, a unique Flory χ interaction parameter, 0.3, was obtained for all samples except for the 28% crystallinity sample. For the latter sample, the lower χ value (0.18) obtained can be explained by a change in the sorption behaviour of the original crystalline domains which may undergo partial destruction. The diffusion coefficient increases with the average water content in the membrane according to an exponential relationship characterized by a limit diffusion coefficient and a plasticization coefficient. The higher the crystallinity of the membrane, the lower the values of the limit diffusion coefficient and the plasticization coefficient. The ethanol sorption was also well described by the Flory-Huggins equation. The limit diffusion coefficient for water was two orders of magnitude larger than that for ethanol.
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    Polymer International 34 (1994), S. 59-72 
    ISSN: 0959-8103
    Keywords: transport ; diffusion ; permeation ; sorption ; Fickian ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Molecular transport as manifested by sorption and diffusion of organic esters into engineering polymer membranes, viz. nitrile butadiene rubber, styrene butadiene rubber, ethylene propylene diene terpolymer, neoprene and natural rubber, has been investigated in the temperature range 25-60°C by the sorption gravimetric technique. The sorption equilibrium for ethylene propylene diene terpolymer was lower than those of the other polymers with all the liquids. Diffusion and permeation coefficients were obtained for the polymer-solvent systems and these follow Arrhenius type behaviour in the temperature range investigated.
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    Polymer International 36 (1995), S. 279-285 
    ISSN: 0959-8103
    Keywords: acrylic polymers ; diffusion ; sorbents ; thermal modification ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Acrylic fibres were modified with ethylene diamine and pyrolysed at temperatures up to 600°C. According to IR spectroscopy, polymers pyrolysed at 300°C contain nitrile and other groups which are present in the initial polymer. The specific surface area is decreased by increasing the pyrolysis temperature. The pore size distribution reveals mainly the presence of macropores. Acrylic polymers and those pyrolysed at 300°C sorb more methylene blue and alizarin yellow from aqueous solution than a non-polar commercial sorbent of high specific surface area. The experimental results for dye sorption were treated theoretically using a diffusion-limited sorption method. The polymers can be ranked by the parameters of this method or their sorption ability. The dye sorption is little affected by the pores of the polymers and is mainly affected by the interactions between the functional groups of the polymers and those of the dyes.
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    Polymer International 36 (1995), S. 353-363 
    ISSN: 0959-8103
    Keywords: diffusion ; Fickian ; sorption ; bromobutyl rubber ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Sorption and diffusion of n-alkanes into bromobutyl rubber membranes were investigated in the temperature interval 25-60°C by a sorption gravimetric method. The Fickian diffusion equation was used to calculate the diffusion coefficients, which were dependent on the size of the alkanes, their interactions with the chain segments of the polymer and temperature. The diffusion coefficients varied from 0.34×10-7 cm2/s (n-hexadecane) to 9.94×10-7 cm2/s (n-hexane). The activation energy for diffusion varied from 14kJ/mol (n-hexane) heptane to 2.0kJ/mol for n-hexadecane. The sorption/swelling results are discussed in terms of first and second order kinetic equations. The molar mass between chain-entanglement-crosslinks was estimated from swelling data. The experimental and calculated results showed a systematic dependence on the increasing size of the alkanes. None of the solvents showed any degradative effects on the polymer.
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    Polymer International 33 (1994), S. 359-365 
    ISSN: 0959-8103
    Keywords: gelatin ; polyelectrolyte ; diffusion ; interferometry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Concentration relations for mutual diffusion coefficients Dm(C) in water of polyelectrolyte gelatin macromolecules at different temperatures were studied by optical interferometry. It is shown that Dm(C) values are in agreement with scaling predictions and are similar to those observed for solutions of neutral macromolecules under θ-conditions. However, they are greatly influenced by the square-law term C2, having a correlation to the conventional scaling law Dm ∝ C, and the mobility of solution components is influenced by physical gelation processes under certain thermodynamic conditions. It is demonstrated that the temperature relation of the diffusion coefficient at infinite dilution D0(C → 0) for the three gelating samples with various physico-chemical properties can be described by a universal function.
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    Polymer International 34 (1994), S. 333-337 
    ISSN: 0959-8103
    Keywords: polyacrylonitrile fibers ; spinning ; zinc chloride ; morphology ; mechanical properties ; diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The structure and mechanical properties of polyacrylonitrile fibers containing small amounts of Zn2+ were investigated. It is possible to interpret the influence of ZnCl2 on the fibers by diffusion. Fibers spun from spinning dope containing ZnCl2 may have a denser and finer structure because ZnCl2 in the spinning dope retards the coagulation rate. The tensile strength and modulus of the fibers are much improved because of the retardation of coagulation. It is probable that the complexation between Zn2+ and CN groups does not contribute to the improvement of the mechanical properties because the amount of ZnCl2 added in a spinning dope is extremely small.
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    Polymer International 35 (1994), S. 257-261 
    ISSN: 0959-8103
    Keywords: non-halo and halo polyesters ; nitroglycerine migration ; inhibitors ; kinetics ; diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The diffusion coefficients (D) of nitroglycerine (NG) migration through cured non-halo and halo polyesters have been calculated with the help of M∞ determined experimentally and Fick's Law. The calculated NG migrations at different time intervals compare very closely with the corresponding NG migrations determined experimentally. The concentration profiles at various locations in thin sheets of non-halo and halo polyesters have also been calculated.
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    Advanced Materials for Optics and Electronics 5 (1995), S. 157-161 
    ISSN: 1057-9257
    Keywords: CdTe ; iodine doping ; diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Studies on the diffusion of iodine into CdTe at a temperature of 20°C using four widely differing types of diffusion sources are compared and discussed. The concentration profiles were measured using either a radiotracer sectioning (RTS) technique or secondary ion mass spectrometry (SIMS).The profiles were composed of four parts to which a computer package consisting of the sum of four complementary error functions (erfc) gave accurate fits, providing four empirical values of the diffusivity. The diffusivities for the fastest component in all four cases were in agreement (∼2 × 10-14 cm2 s-1) and were consistent with previously published data. These results indicate that when iodine is diffused from the vapour it is not a suitable long-termstable dopant in devices where sharp junctions are required.
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    Polymer International 38 (1995), S. 299-303 
    ISSN: 0959-8103
    Keywords: skin membranes ; hole formation ; diffusion ; polyetherimides ; videomicroscopy ; solvent diffusion coefficient ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It is shown quantitatively that the formation of holes through the skin of membranes, prepared by the quick immersion in water of polyetherimides in solution in N-methylpyrrolidone, is governed by the solvent mobility. The surface pattern observed by videomicroscopy exhibits a characteristic distance between neighbouring holes (≃5 μm) which is a linear function of D-1s; Ds is the solvent diffusion coefficient in the polymeric solution, measured using a pulsedfield gradient NMR technique. The dependence of this distance on the solvent concentration in water is also characterized.
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    Polymer International 41 (1996), S. 73-78 
    ISSN: 0959-8103
    Keywords: ionomer ; permeation ; diffusion ; sorption ; gas ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Transport properties of oxygen and carbon dioxide in three ethylene-acrylic acid ionomers, characterized by different amounts of acrylic acid groups, percentage of neutralization and counterion type, have been investigated. Gas permeation experiments have been performed in the 25-65°C range. Gas permeabilities, diffusivities and solubilities were evaluated along with activation energies and heats of solution. The transport properties have been analysed in order to correlate the effect of counterion type and its concentration on macromolecular mobility and on polymer-gas interaction, which in turn are the factors determining permeation rate.
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    Surface and Interface Analysis 25 (1997), S. 948-951 
    ISSN: 0142-2421
    Keywords: SIMS ; thin film ; imaging ; diffusion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The diffusion of D2O into and through oxide films on Zr—Nb alloys was investigated using secondary ion mass spectrometry (SIMS) image analysis. In preparation for this, the microscopic structures of the oxide were studied in relation to the grain structures in the underlying alloy. On alloys containing low concentrations of niobium (1-2.5 wt.%), the oxide was found to exhibit more localized growth, particularly above grain boundaries in the alloy. Such oxide regions appeared to be considerably more porous to D2O ingress. By contrast, the oxide film on the Zr 20 wt.% Nb alloy was found to be the most resistant to D2O ingress; no local regions of higher porosity could be found. © 1997 John Wiley & Sons, Ltd.
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    International Journal for Numerical and Analytical Methods in Geomechanics 20 (1996), S. 571-593 
    ISSN: 0363-9061
    Keywords: methane gas ; finite element ; coal mining ; diffusion ; adsorption ; outbursts ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: This paper presents the development of a mathematical model for methane gas migration in coal seams. The major focus of this model is the coupling between the gas flow and deformation of solid coal. The effect of diffusion of adsorbed methane gas from the solid matrix to the voids has been taken into account. The adsorption of gas in the coal seam causes a two-phase state of gas flow. The governing equation for the two-phase gas flow is a non-linear partial differential equation with non-linear boundary conditions. A finite element model has been developed for simulation of the distribution of pressure and concentration of methane gas due to gas migration in coal seams.
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    International Journal for Numerical and Analytical Methods in Geomechanics 20 (1996), S. 693-713 
    ISSN: 0363-9061
    Keywords: unfrozen layer ; osmotic ; diffusion ; transport ; moisture ; temperature ; optimization ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Two series of freezing column tests with distilled water and municipal solid waste leachate were investigated, using illitic silty clay. Temperature distributions along the freezing column were recorded as a function of distance and time. Unfrozen moisture content and osmotic pressures as a function of temperature were calculated.It was shown that temperature distributions as a function of distance and time were similar in all tests, probably as a result of the limited amount of moisture intake. The amount of moisture intake was directly related to freezing time and temperature gradient in the freezing column. Unfrozen moisture contents, ion concentrations and temperature gradients were identified as the controlling parameters that contributed to the boundary layer transport (BLT) of metal ions in frozen specimens. Na+ concentration profiles were mostly dependent on water movement in the freezing column. The behaviour of Ca2+ and Mg2+ cations was similar to Na+; their concentrations in the soil solution decreased with freezing time due to ion exchange.Temperature, moisture content in an unfrozen boundary layer (UBL), and concentration gradient were taken into consideration in the development of a boundary layer transport model (BLTM). Based on the experimental results and Powell's optimization technique, the diffusivity parameters of various metal ions were calculated. Comparison of experimental and predicted results indicated that the BLTM can predict the migration of metal ions in UBL.
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    International Journal for Numerical and Analytical Methods in Geomechanics 22 (1998), S. 575-595 
    ISSN: 0363-9061
    Keywords: contaminant transport ; variable density flow ; fractures ; leakage ; dispersion ; diffusion ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: A numerical model for simulating flow and transport of contaminants with variable density in fractured porous media is presented. The non-linearities arising from the density variation and the velocty-dependent dispersion terms have been handled by Picard method. It is shown that the contaminant transport in a fractured porous medium is initially dominated by fractures. However, with time increasing, the contaminant concentration in porous blocks increases, due to the leakage of contaminant from the fracture network to the porous blocks. It is also shown that the high density of contaminant has a greater effect on its transport in the fracture network than in the porous blocks. © 1998 John Wiley & Sons, Ltd.
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