High pressure stability of bismuth sillenite: A Raman spectroscopic and x-ray diffraction study J. Appl. Phys. 108, 083508 (2010); 10.1063/1.3496659High-pressure x-ray diffraction and Raman spectra study of indium oxide J. Appl. Phys.Polyacetylene film and bulk samples were prepared by polymerization of acetylene in the presence of a jJ.-(J{'I15-cyclopentadienyl)-tris ('I1-cyclopentadienyl) dititanium (Ti-Ti) catalyst in hexane. Conducting films (0"R.T.-25 O-I.cm-I) or bulk polymer samples (O"R.T-l 0-1 • em-I) were prepared by treatment of the nascent polymer with solutions of iodine in hexane. Raman, x-ray photoelectron, and x-ray diffraction techniques were used to characterize these polyacetylene-iodine derivatives. The measurements are consistent with the presence of iodine in two different forms, 13 and possibly 1 5 , Although the concentration of the iodine varied in different samples (40%-70% by weight), in all cases the amount of the second species decreases irreversibly upon thermal annealing or the application of high mechanical stresses. X-ray diffraction measurements suggest that iodine species intercalate in sheets parallel to a close packed plane of the polyacetylene. Valence band x-ray photoelectron spectroscopy measurements on an iodinated cis-rich polymer film show a finite density of states at the Fermi level. This observation is consistent with metallic conductivity in the sample.106
The structures of cis-polyacetylene and polyacetylene–iodine derivatives have been investigated by x-ray diffraction and crystal packing analysis. Results obtained for cis-polyacetylene are consistent with the space group Pnma with one CH per asymmetric unit and a chain symmetry (m1̄)t. Hence, the structure is analogous to that of orthorhombic polyethylene. For a structure with such a concentration of π electrons there is minimal overlap between parallel π orbitals. The π orbitals are almost orthogonal for four of the six closest neighbors of a given chain. Based on x-ray diffraction and spectroscopic results, a model is proposed for the structure of the highly conducting polyacetylene–iodine complexes. According to this model, linear arrays of polyhalide ions (principally in the form of I−3) substitute in positions of displaced polyacetylene chains. At high dopant concentrations, alternate close-packed layers of polyacetylene are separated by a layer consisting of such polyhalide arrays. This model predicts a limiting charge transfer of 0.11 electron on the average per carbon atom in the polyacetylene chain.
Crystallinities of films of copolymers of chlorotrifluoroethylene with 0 to 4% vinylidene fluoride, different molecular weights and thermal histories were calculated from differential scanning calorimetry (DSC), X‐ray diffraction (XRD), and density measurements. The crystallinities for these films range between 16 to 58%, 11 to 71%, and 13 to 77% as determined by DSC, XRD, and density, respectively. Although the numerical value of the DSC, XRD, and density crystallinities obtained by each of the techniques are different, they correlate well with each other. The primary source of error in DSC is the uncertainty in drawing the baseline for separating the heat of fusion and heat of crystallization. In XRD, the ambiguities in the separation of the amorphous and crystalline peaks reduce the precision of the results. Calculation of crystallinity from density values requires that the distribution of the VF2 between the amorphous and crystalline regions be known. In addition, the density technique is not sensitive to variations in the crystalline and amorphous densities.
SynopsisA series of metal and acid salts having poly(alkylbenzimidazo1es) as the parent ligand were synthesized. The room-temperature electrical resistivity of the parent and the salts was measured. Values for the dc electrical resistivity varied from -1 X 1013 ohmcm for the neutral polymers to -1 X lo6 ohmecm for the acid conjugate formed by reaction with HC1. Unexpectedly, changes in resistivity did not correlate with acid strength as measured by us but could be roughly correlated with the molar volume of the corresponding acid or metal salt. The nature of the complexes was elucidated using the ESCA technique. The electron core levels of nitrogen, chlorine, and the various metals were examined. The observed photoelectron spectra indicated the formation of polybenzimidazole/acid and polybenzimidazole/metal salts. In addition, one was able to conclude that the complexes of Co and Ni were high spin, thus ruling out a planar geometry for the Ni(I1) complex.
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