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  • 1
    Electronic Resource
    Electronic Resource
    Phase equilibria in SBR/polybutadiene elastomer blends: Application of Flory-Huggins theory (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 1053-1062 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of anionically-polymerized polybutadiene (BR) and styrene-butadiene copolymer (SBR) must be treated as mixtures of terpolymers and tetrapolymers, due to the presence of three different BR isomers: cis-1,4, trans-1,4, and vinyl-1,2. Moreover, in the absence of specific interactions or chemical reactions that strongly influence miscibility, structural characteristics of the component polymers, such as BR isomer content, SBR styrene content, monomer sequence distribution, molecular weight, and molecular weight distribution, are expected to have an increased role in determining the blend miscibility characteristics. Small angle neutron scattering (SANS) studies of SBR/BR blends have resulted in the computation of the monomer-monomer segmental interaction energetics via a Flory-Huggins treatment. This allows quantitative prediction of miscibility behavior as a function of polymer structure. We have used the Flory-Huggins chi parameters, describing the styrene/cis-1,4, styrene/trans-1,4, and cis-1,4/trans-1,4 segmental interactions, to identify certain blend combinations expected to exhibit phase transitions in an experimentally accessible temperature range. The appropriate polymers were synthesized, solution blended, and the blends analyzed via optical microscopy and thermal analysis. Our results show that the blend behavior, observed experimentally, is consistent with the calculated cloud point curves. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070510611
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  • 2
    Electronic Resource
    Electronic Resource
    The molecular weight average obtained by combining quasielastic light-scattering and intrinsic viscosity measurements (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 3261-3267 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: For “monodisperse”, randomly coiled macromolecules, we find that the molecular weight, intrinsic viscosity, and diffusion coefficient are accurately related by \documentclass{article}\pagestyle{empty}\begin{document}$$ \left[ \eta \right]M_{D,\eta } = 3.0 \times 10^{ - 27} \left( {D_t^0 {{\eta _0 } \mathord{\left/ {\vphantom {{\eta _0 } T}} \right. \kern-\nulldelimiterspace} T}} \right)^{ - 3} {{\left( {{{{\rm erg}} \mathord{\left/ {\vphantom {{{\rm erg}} {^\circ {\rm K}}}} \right. \kern-\nulldelimiterspace} {^\circ {\rm K}}}} \right)^3 } \mathord{\left/ {\vphantom {{\left( {{{{\rm erg}} \mathord{\left/ {\vphantom {{{\rm erg}} {^\circ {\rm K}}}} \right. \kern-\nulldelimiterspace} {^\circ {\rm K}}}} \right)^3 } g}} \right. \kern-\nulldelimiterspace} g} $$\end{document} This equation holds for denatured proteins in 6M GuHCl(aq) as well as for narrow polystyrene fractions in tetrahydrofuran. For a Schulz distribution of molecular weights, the weight measured from combining diffusion and viscosity data is closely approximated by \documentclass{article}\pagestyle{empty}\begin{document}$$ M_{D,\eta } = M_w^{0.425} M_z^{0.575} $$\end{document} These equations are verified with measurements of wide molecular distributions of polystyrene in toluene and data from the literature. These relations provide a rapid, nondestructive method to determine a well-specified molecular weight average of small quantities of polymers in a wide diversity of solvents using quasielastic light scattering techniques to evaluate polymer diffusion coefficients.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1977.070211207
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  • 3
    Electronic Resource
    Electronic Resource
    Studies of ESR Nitroxide probe mobility in polymer blends (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 27 (1989), S. 2553-2560 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report studies of the temperature-dependence of the ESR spectrum of the nitroxide spin radical 4-(2-bromoacetamide)-2,2,6,6 tetramethyl-1-oxyl piperidine (BRAMO) dispersed in poly(vinylidene fluoride) (PVDF), poly(methyl methacrylate) (PMMA), poly(vinyl acetate) (PVAc), and PVDF/PMMA and PVAC/PMMA blends of varying composition. In PVDF/PMMA blends which show a single composition-dependent Tg, the mobility of BRAMO is identical to that in pure PMMA. On the other hand, in PVAC/PMMA blends, the mobility of BRAMO corresponds to that in pure PVAC. The results suggest that (1) BRAMO selectively binds to polymers based on hydrogen bonding affinity, (2) the spin probe is sensitive to segmental motions on a length scale shorter than those which give rise to the glass transition, and (3) compatible polymer blends are heterogeneous on the length scale of the BRAMO probe (ca. 8.3 Å).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1989.090271211
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  • 4
    Electronic Resource
    Electronic Resource
    Study of free volume in high-vinyl polybutadiene/cis-polyisoprene blends using positron annihilation spectroscopy (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 861-871 
    Details
    ISSN: 0887-6266
    Keywords: glass transition ; polymer blends ; free volume ; positron annihilation ; composition dependence of Tg ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: High-Vinyl Polybutadiene (HVBD)/cis-Polyisoprene (CPI) blends were characterized by Differential Scanning Calorimetry (DSC) and Positron Annihilation Lifetime Spectroscopy (PALS). A single DSC glass transition temperature Tg is observed, whose composition dependence strongly deviates from additivity, and shows an apparent cusp when the weight fraction of HVBD ≈ 0.75. The free-volume hole size, Vh, and the scaled fractional free volume, hps/C, = I3Vh were determined by PALS from the orthopositronium (o-Ps) intensities, I3, and lifetimes, τ3, over a temperature range encompassing Tg and the temperature at which “positronium bubble” formation occurs. In the glass, Vh and hps/C are smaller for CPI than for HVBD, but the thermal expansion coefficient for hole volume, αf, is larger in the melt for CPI than for HVBD; thus, an iso-hole volume temperature occurs in these blends at Tiso ≈ -34°C. Above and below Tiso, Vh and hps/C each show a negative departure from additivity. A quantitative interpretation of the cusp in the composition dependence of Tg can be obtained, via a modified analysis of Kovacs, using free-volume quantities from PALS, with the ratio of scaling constants CCPI/CHVBD as an adjustable parameter. At high temperatures, the positron bubble size is smaller in CPI than in HVBD. This agrees with the observation that the thermal expansivity of hole volume, and, hence the internal pressure are larger in the equilibrium melt of CPI. The effect of e+-irradiation on the o-Ps intensity was investigated. I3 decreases more rapidly in the melt as T → Tg, and then more slowly in the glass, suggesting that the effect is due to trapping of radical or ionic species which inhibit o-Ps formation. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 861-871, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Thermal history and temperature dependence of viscoelastic properties of polymer glasses: Relation to free volume quantities (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 2295-2305 
    Details
    ISSN: 0887-6266
    Keywords: free volume ; viscoelastic properties ; physical aging ; the Doolittle equation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependence of physical properties on temperature and thermal history of glassy polycarbonate is examined. The average stress relaxation time increases during isothermal aging and with decreasing cooling rate. The temperature dependence of the stress relaxation time was compared with a free volume function calculated from specific volume data reported by Zoller by means of the Simha-Somcynsky theory and with a fractional free volume measured by ortho-positronium annihilation. We report in addition comparisons between free volume fractions extracted from volume data, and creep measurements for polystyrene, and stress relaxation data for poly(vinyl acetate) given by Kovacs et al., Schwarzl and Zahradnik, and Meyer et al. These investigations suggest that in the glassy state the Doolittle equation is valid only in isothermal aging experiments. It follows that in expressing the polymer mobility not only a temperature-dependent free volume but additional temperature-dependent processes need to be considered. © 1995 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090331701
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  • 6
    Electronic Resource
    Electronic Resource
    Free volume quantities and viscoelasticity of polymer glasses (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1423-1426 
    Details
    ISSN: 0887-6266
    Keywords: viscoelastic properties ; positron annihilation spectroscopy ; physical aging ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have investigated, in terms of the Cohen-Turnbull theory, a relationship for polycarbonate (PC) glasses between average stress relaxation times, 〈to, and average free volume sizes, 〈vf〉, obtained from positron annihilation lifetime spectroscopy. This examination suggests that the minimum free volume required for stress relaxation, v*, decreases with decreasing temperature and that, near the glass transition temperature, only a subset of extremely large free volume elements contributes to the stress relaxation of PC glasses. This suggestion is consistent with the idea that near the glass transition temperature, the viscoelastic response is dominated by large-scale, main-chain motion, whereas at lower temperature it is controlled by local motion. Moreover, comparison with the v* value estimated from gas diffusivity through various PC species at room temperature shows that the required free volume size for stress relaxation in the glass transition region is much larger than that for gas diffusion. Previously we showed that the Doolittle equation fails to correlate viscoelastic relaxation times of polymer glasses with changing temperature; determining the free volume fraction, h, from theoretical analysis of volume recovery data and theory, the Doolittle equation is shown to be valid in PC above 135°C (Tg - 14°C) irrespective of temperature and physical aging times. This result supports the idea suggested in the previous article that, as glassy polymers approach the transition region, viscoelastic properties increasingly tend to be controlled by free volume. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Viscoelastic properties of dilute nematic mixtures containing cyclic and hyperbranched liquid crystal polymers dissolved in a nematic solvent (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1213-1223 
    Details
    ISSN: 0887-6266
    Keywords: viscoelastic properties ; dynamic light scattering ; dilute nematic solutions ; cyclic liquid crystal polymer ; hyperbranched liquid crystal polymer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The twist and bend viscosities of dilute solutions of cyclic and hyperbranched liquid crystal polymers (LCP) dissolved in low molar mass nematic solvents were determined via dynamic light scattering analysis. These results were compared to those of linear chains with similar chemical repeat structures. The nematic solvent used was 4′-pentyloxy-4-cyanobiphenyl (50CB). The cyclic LCP oligomers, Cy TPB10, have a mesogenic group, 1-(4-hydroxy-4′-biphenyl)-2-(4-hydroxyphenyl) butane, separated by flexible decamethylene spacers. The twist viscosity of the cyclic Cy-TPB10 oligomers increases with molecular weight more strongly than the linear, TPB-10, suggesting that the hydrodynamic behavior of Cy-TPB10 is closer to that of a rigid rod than TPB10. Surprisingly, the intrinsic bend viscosity [ηbend] of Cy-TPB10 decreases with molecular weight, in contrast to the positive dependence for linear TPB10. This may reflect the higher strain energy in the smaller ring sizes. The hyperbranched LCP, TPD-b-8, is also based on the mesogen 10-bromo-1-(4-hydroxy-4′-biphenyl)-2(4-hydroxyphenyl) decane but with octyl groups at the chain ends. We compare the viscoelastic behavior of dilute nematic solutions of TPD-b-8 in 50CB against that of a linear main-chain LCP, TPB7, with the same mesogenic group but with heptamethylene spacers. The viscometric properties of TPD-b-8/50CB and TPB7/50CB are quite different. The results suggest that each chain is prolate (i. e., R∥ 〉 R⊥) but that TPD-b-8 has a smaller chain anisotropy than that of TPB7. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090330807
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  • 8
    Electronic Resource
    Electronic Resource
    Monte Carlo calculations of hole size distributions: Simulation of positron annihilation spectroscopy (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 1429-1435 
    Details
    ISSN: 0887-6266
    Keywords: positron annihilation lifetime spectroscopy ; lattice model ; Monte Carlo ; hole size distribution ; bisphenol-a polycarbonate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Consequences are explored of a hole size distribution in an amorphous polymer for the ortho-positronium (o-Ps) lifetime (τ3) and intensity (I3), determined by positron annihilation lifetime spectroscopy. The disordered lattice model, with a vacancy fraction h as a central quantity, is used to represent the equation-of-state behavior of the polymer. By means of Monte Carlo simulations, we obtain the cluster size distribution as a function of h and hence temperature. The predicted average cluster size and the cluster concentration are compared to τ3 and I3 data, respectively, for bisphenol-a polycarbonate. Furthermore, the influence of an o-Ps lifetime distribution on the experimental mean τ3 is investigated. By mimicking the computational methods used in experimental analysis, agreement between experiment and theory in respect to τ3 and to I3 in the melt ensues. In the glass, however, the experimental I3 becomes increasingly smaller with decreasing temperature than is computed. These deviations may result from a distortion of the equilibrium free volume. © 1992 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090301301
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular weight-dependence of free volume in polystyrene studied by positron annihilation measurements (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2637-2644 
    Details
    ISSN: 0887-6266
    Keywords: free volume in amorphous polymers ; positron annihilation measurements ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Positron annihilation lifetime measurements are reported for four monodisperse polystyrenes with molar mass M = 4,000, 9,200, 25,000, and 400,000. The temperature dependences of orthopositronium (o-Ps) lifetime (τ3) and intensity (I3) were measured from 5°C to Tg + 30°C for each sample. From these data, the free volume hole size, 〈vf(τ3)〉, and fractional free volume hps=CI3〈vf(τ3)〉 were calculated. The temperature dependences of τ3, 〈vf(τ3)〉 and hps show a discrete change in slope at an effective glass transition temperature, Tg,ps, which is measurably below the conventional bulk Tg. This suggests that τ3 is sensitive to large holes which retain their liquid-like mobility in the glassy state. Good agreement was found for T 〉 hg,ps between hps and the theoretical free volume fraction hth deduced from experimental P-V-T data for polystyrene using the statistical mechanical theory of Simha and Somcynsky. Below Tg,ps, deviations between hps and hth are observed, hps falling increasingly below hth as temperature decreases. Whereas hps and hth depend strongly on M in the melt, each essentially independent of M in the glass. A free volume quantity, computed from the bulk volume, which is in good numerical agreement with the Simha-Somcynsky h-function in the melt, gives improved agreement with hps in the glassy state. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090321609
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  • 10
    Electronic Resource
    Electronic Resource
    Rapid characterization of protein molecular weights and hydrodynamic structures by quasielastic laser-light scattering (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1283-1299 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two methods for the characterization of protein molecular weights from their diffusion coefficients are discussed. These measurements can be made quickly and reliably at low concentrations using quasielastic light-scattering techniques. First, an empirical calibration of the diffusion coefficient at infinite dilution of denatured random coils against molecular weight is reported. The second method combines the measurement of D0 with the intrinsic viscosity [η]. This D0-[η] relationship proves to be very insensitive to polymers structure or solvent type. The data indicate that the ratio of the hydrodynamic radius measured by viscosity to the hydrodynamic radius measured by diffusion is about 15% smaller than that predicted by theoretical models. The nature of the molecular-weight average obtained for polydisperse systems is defined for a Schulz distribution. These hydrodynamic methods have also been used to demonstrate the presence of chain branching in the glycoprotein ovomucoid. In addition, a method is proposed by which the effective segment length and an excluded volume parameter for random coils may be evaluated for diffusion measurements.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150706
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