Polymer Relaxational Dynamics Associated With Ionic Conduction in Confined Geometry

2002 ◽  
Vol 756 ◽  
Author(s):  
J.-M. Zanotti ◽  
L. J. Smith ◽  
E. Giannelis ◽  
P. Levitz ◽  
D. L. Price ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Ionic Conduction ◽  
Inelastic Neutron Scattering ◽  
Mean Square Displacement ◽  
Lattice Relaxation ◽  
Inelastic Neutron ◽  
Spin Lattice Relaxation ◽  
Scattering Data ◽  
Melting Transition ◽  
Time Data

ABSTRACTResults of a quasi-elastic incoherent neutron scattering study of the influence of confinement on polyethylene oxide (PEO) and (PEO)8Li+[(CF3SO2)2N]- (or (POE)8LiTFSI) dynamics are presented. The confining media is Vycor, a silica based hydrophilic porous glass. We observe a strong slowing down of the bulk polymer dynamics under presence of Li salt. The confinement also affects dramatically the apparent mean-square displacement of the polymer. As supported by DSC measurements, the PEO melting transition at 335 K is strongly attenuated under confinement, suggesting that confinement modifies the global structure of the system, increasing the fraction of amorphous PEO by respect to crystalline phase. Local relaxational PEO dynamics is successfully described by the DLM (Dejean-Laupretre-Monnerie) model usually used to interpret NMR spin-lattice relaxation time data. The scattering vector dependence of the correlation times deduced from inelastic neutron scattering data is found to obey a power-law dependence. DSC and preliminary ionic conduction measurements are also presented.

scholarly journals CH3 Rotational Tunnelling in Alkali Acetates and Correlation between NMR Spin-Lattice Relaxation and Neutron Scattering Data

1985 ◽  
Vol 40 (6) ◽  
pp. 596-601 ◽  
Author(s):  
A.-S. Montjoie ◽  
W. Miiller-Warmuth
Keyword(s):  
Activation Energy ◽  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Larmor Frequency ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Scattering Data ◽  
Relaxation Rates ◽  
Tunnel Splitting ◽  
Spin Lattice

NMR spin-lattice relaxation rates l / T1 have been measured at 15 and 30 MHz and various temperatures in polycristalline sodium and potassium acetate. The results for CH3COONa are characteristic of methyl group tunnelling with a frequency which is very much larger than the NMR Larmor frequency. Derived values of the torsion energy (1.1 kJ/mol) and the ground state tunnel splitting (5.6 meV) agree with data obtained from inelastic neutron scattering by Clough et al. The shape of the hindering potential and the activation energy for classical reorientation (3.2 kJ/mol) have been determined. Since the relaxation rate of CH3COOK is a superposition of at least two mechanisms, in this case the results are less accurate and refer to one type of CH3 rotor only: activation energy 5.4 kJ/mol, tunnel splitting 0.23 meV. Comparison is made between tunnel splittings and classical activation energies for the acetates and various other materials: strong correlations are demonstrated and discussed.

scholarly journals Methyl Group Rotation and Tunnellingin Crystals of 5-Membered Ring Molecules

1988 ◽  
Vol 43 (1) ◽  
pp. 35-42 ◽  
Author(s):  
A.-S. Montjoie ◽  
W. Müller-Warmuth ◽  
Hildegard Stiller ◽  
J. Stanislawski
Keyword(s):  
Elevated Temperatures ◽  
Inelastic Neutron Scattering ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Inelastic Neutron ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Quantum Tunnelling ◽  
Spin Lattice

Abstract1H NMR spin-lattice relaxation times T1 and -if accessible -level-crossing peaks and inelastic neutron scattering spectra have been measured for solid 2-and 3-methylfuran, 2-and 3-methylthiophene, 3-and 4-methylpyrazole, 1-methylimidazole, and 5-methylisoxazole. From the tunnel splittings, the torsional excitations and the NMR relaxation rates, the molecular dynamics of the methyl rotators has been evaluated between the limits of quantum tunnelling at low temperatures and thermally activated random reorientation at elevated temperatures.

scholarly journals Hydrogen Vacancy Diffusion Parameters in ScH2-x and ScD2-x from 45Sc Spin-Lattice Relaxation Time Measurements

1985 ◽  
Vol 40 (3) ◽  
pp. 222-228
Author(s):  
M. Jerosch-Herold ◽  
L.-T. Lu ◽  
D. R. Torgeson ◽  
D. T. Peterson ◽  
R. G. Barnes ◽  
...  
Keyword(s):  
Inelastic Neutron Scattering ◽  
Lattice Relaxation ◽  
Inelastic Neutron ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Vacancy Diffusion ◽  
Arrhenius Behavior ◽  
Spin Lattice ◽  
Diffusion Parameters ◽  
Hydrogen Deuterium

The temperature dependence of the nuclear spin-lattice relaxation rate R1 of 45Sc has been measured in scandium dihydrides and dideuterides. These data are satisfactorily accounted for by two contributions to R1, R1e due to conduction electrons, and R1Q due to quadrupole interaction fluctuations resulting from vacancy diffusion on the hydrogen (deuterium) sublattice. Describing these fluctuations by a Lorentzian spectral density and Arrhenius behavior for the vacancy hopping, analysis of the data yields values of the Korringa product A = T/R1e and the activation energy Ea and attempt frequency v0 for vacancy-diffusion. In contrast to v0 values based on proton measurements, the 45Sc results agree satisfactorily with the value based on inelastic neutron scattering measurements of hydrogen optic mode vibration frequencies, v0 ≅ 2 x 1014s-1. We conclude that hydrogen-hydrogen interactions are responsible for the lower v0 values derived from proton R1 measurements.

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