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  • 1
    Electronic Resource
    Electronic Resource
    Elastic and dynamic properties of polymer electrolytes: A Brillouin scattering study of poly(propylene glycol)–NaCF3SO3 complexes (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 655-662 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the present study of ion conducting polymers we demonstrate how light scattering can be used to obtain information about the elastic properties and the local intrachain mobility, which are essential characteristics of a high performance polymeric solid electrolyte. Brillouin scattering has been applied in studies of sodium triflate (NaCF3SO3)–poly(propylene glycol) (PPG) complexes of concentrations O:M=5:1, 8:1, and 16:1, where O:M is the backbone oxygen to sodium ratio. From the spectra sound velocity and absorption data were obtained. The acoustic data reveal structural relaxation processes associated with local translational (and orientational) intrachain motions of the polymer segments. The characteristic relaxations times τ were determined and found to be strongly dependent on the concentration of the dopant salt. This is because the dissociated ions act both as crosslinks betwen polymer chain segments and as "free'' ions available for conduction. Therefore, as the concentration of dissociated ions increases the intrachain mobility is slowed down (τ increases) due to increased crosslinking. The effect is demonstrated in the hypersonic velocity dispersion curve and in the absorption peak which both shift to higher temperatures with increasing salt concentration. The shift correlates with the increase in the glass transition temperature as salt is added to the polymer. It also correlates, at least at low salt concentrations, with the concentration of dissocated ions and with the conductivity. It can be concluded that the motions of free ions responsible for charge transport are strongly coupled to the intrachain motions of the polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457171
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  • 2
    Electronic Resource
    Electronic Resource
    The pressure variation of the glass transition temperature in atactic polystyrene (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 1006-1014 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Brillouin frequency shifts from light scattering are used to measure the variation with pressure of the zero-frequency glass transition temperature Tg in atactic polystyrene (PS) at pressures up to 3 kbar. These results are extrapolated to high pressures and compared with theoretical predictions. Experimentally it is found that Tg asymptotically approaches a critical value at high pressures. The equilibrium lattice model of DiMarzio, Gibbs, Fleming, and Sanchez which approximates the residual entropy of a polymeric glass correctly predicts the experimentally observed trends. The molecular theory of Bengtzelius, Götze, and Sjölander is also qualitatively correct at high pressures even though it deals with the glass transition of a classical monatomic fluid. Neither theory is quantitatively in agreement with our results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450633
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  • 3
    Electronic Resource
    Electronic Resource
    Raman and Brillouin scattering of LiClO4 complexed in poly(propylene-glycol) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2038-2043 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman spectra of LiClO4 complexed in poly(propylene-glycol) (PPG) have been obtained for concentrations of the monomer to salt ratio (ether oxygen):Li in the range 30:1–5:1. Splitting of the symmetric stretching mode of the ClO4− anion was observed with an intensity profile that varied with salt concentration. This phenomenon indicates a changing environment about the anion. A two-component band analysis leads to the identification of dissociated ions on one hand and solvent-separated ion pairs on the other. The concentration of ion pairs is relatively low compared to that of the dissociated ions, which are predominant for all concentrations. Despite the observed increase in the absolute number of dissociated ions at higher salt concentration, the electrical conductivity is reported to decrease in the same range. This indicates that the number of "free'' charge carriers is of less importance for the conductivity than the mobility, which is damped in this concentration range. Frequency shifts of the disordered longitudinal-acoustic mode and increased hypersonic velocities, measured with Raman and Brillouin scattering techniques, respectively, indicate increased stiffness of the polymer matrix for increasing salt concentration, which probably results in decreased ion mobility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341709
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  • 4
    Electronic Resource
    Electronic Resource
    Pressure Variation of the Glass Transition Temperature in Atactic Polystyrene (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 484 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb49588.x
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  • 5
    Electronic Resource
    Electronic Resource
    Statistical methodology for setting legal allowances for nutrient contents of bagged fertilizer materials in the State of North Carolina (1988)
    Springer
    Nutrient cycling in agroecosystems 18 (1988), S. 71-99 
    Details
    ISSN: 1573-0867
    Keywords: Commercial fertilizer ; hierarchical sampling ; investigational allowances ; legal allowances ; sampling ; tolerances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The process of establishing investigational allowances for fertilizer materials is reviewed. All sources of variation incurred in taking, preparing and analyzing an official sample of fertilizer are considered. The importance of both theoretical and practical considerations is discussed. Use of the techniques described is illustrated using a set of data involving five grades of commercial fertilizer. Sampling was by a hierarchical scheme. Estimates of variance components from these data were used in the estimation of the investigational allowances. Economic losses to the State of North Carolina, the farmers, and the manufacturer were estimated using various assumed prices and legal allowance establishment procedures. Setting the investigational allowances at 2.33 standard errors is confirmed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01064180
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