Using neutron diffraction, the structural change of a backbone polymer, polybutadiene, is studied when heated from the glass to the melt. On a microscopic scale the temperature dependence of the linear thermal expansion shows a discontinuity below the calorimetric glass transition temperature Tg, whereas the correlation length for monomer or chain ordering becomes independent of temperature near Tg. These effects appear in the range where we recently have observed changes in the inelastic excitation spectrum of this sample.

1H NMR solid state techniques have been used to study bonding properties, location, and mobility of hydrogen in various phases of the hydrogen bronze HxMoO3. Temperature-dependent spectra characteristic of different degrees of intercalation have been observed, and furthermore, from measurements of the relaxation rate, dynamic properties have been derived. There is strong evidence of intralayer hydrogen positions on a quasi-one-dimensional zig–zag line connecting the vertex-sharing oxygen atoms of the MoO6 octahedra and these are first occupied if the degree of intercalation x is low. For x>0.85 the hydrogen in excess starts to fill up interlayer positions coordinated with terminal oxygen atoms at the van der Waals gap. Both isolated and paired protons have been detected in the interlayers, whereas clusters or pairs appear along the zig–zag lines. Hydrogen separations within the clusters, bonding with oxygen and charge transfer to the conduction band of the host lattice, are discussed. Hydrogen diffusion changes from being predominantly one-dimensional to three-dimensional in character as x increases. The activation energies of the motion are of the order of magnitude of 15 to 30 kJ/mol.

The 1H NMR has been studied in the hydrogen bronzes H0.35MoO3 and H0.33WO3 prepared by galvanostatic cathodic reduction. Both systems reveal an extreme anisotropy of the hydrogen mobility due to quasi‐one‐dimensional behaviour. – In H0.35MoO3 the temperature dependent 1H wideline data give strong evidence that hydrogen is clustered in quasi‐one‐dimensional channels. Analysis of the temperature dependence of the second moment M2, the transverse relaxation time T2, and the spin‐lattice relaxation time T1 yields essentially the same valueEA = 30 kJ/mol for the activation energy of the translational motion of hydrogen within the channels. In H0.33WO3 evidence for the quasi‐one‐dimensional behaviour is provided by the frequency dependence of T1 and the marked non‐exponential recovery of the nuclear magnetization in the vicinity of the T1 minimum. The activation energy for the translational motion is EA = 3.6 kJ/mol only, indicating high mobility of hydrogen in this bronze.

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