RAMAN SCATTERING FROM OLIGOMERS OF POLYTETRAFLUOROETHYLENE AND A HIGHLY ORIENTED (TFE-HFP) COPOLYMER MONOFILAMENT
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Date
1977
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Ohio State University
Abstract
The Raman spectra of a series of perfluoro n-alkanes (e.g., $C_{10}F_{22}, C_{20}F_{42})$ show several band progressions as a function of chain length. These data can be used to plot out portions of the dispersion curves near the Brillouin zone center. A comparison with the dispersion curves calculated for polytetrafluoroethylene (PTFE) using the force fields which are currently $available^{1,2}$ will be made. Of particular interest is the $\nu_{8}$ longitudinal acoustic branch from which a value of the crystalline Young’s modulus (along the fiber axis) for a helical FTFE molecule can be determined. In addition, polarization data were obtained from a highly oriented filament of a tetrafluoroethylene (TEF) - hexafluoropropylene (HFP) random copolymer. The use of several scattering geometries has allowed us to make symmetry assignments of the observed bands. We found that the previous assignment schemes were inconsistent with the polarization results; in particular, the 291 $cm^{-1}$ band has been found to belong to the $E_{1}$ rather than the A symmetry species as was intially $believed.^{1.2}$ The implication of these results on current force field models will be discussed.
Description
$^{1}$ F. J. Boerio and J. L. Koenig, J. Chem. Phys. 52, 4826 (1970). $^{2}$ L. Piseri, B. M. Powell, and G. Dolling, J. Chem. Phys. 58, 158 (1973).
Author Institution: Institute for Materials Research, National Bureau of Standards
Author Institution: Institute for Materials Research, National Bureau of Standards