L. J. Garfield
Mar 7, 2007
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Influential Citations
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Journal
Journal of Polymer Science Part C: Polymer Symposia
Abstract
Molecular motions in the bulk polycarbonates of bis(4-hydroxyphenyl)-2,2-propane, bis(4-hydroxyphenyl)hexafluoro-2,2-propane, and bis(4-hydroxyphenyl)1,3-dichloro, tetrafluoro-2,2-propane have been studied by wide-line nuclear magnetic resonance techniques. Magnetic resonance information obtained over a broad temperature range from both H1 and F19 nuclei has been used to assign various mobility phenomena to specific segments of the macromolecules. Furthermore, because of the close similarity in size of the fluorine and hydrogen atoms, F19 resonance information yields some further insights on molecular motions in BPA polycarbonate. The rotation of -CF3 groups, which begins at 283°K, is apparently cooperative with the motion of the adjacent phenyl groups. The effect of the -CF3 groups on the restricted motion of the adjacent phenyl groups is the same as that of -CH3 groups. Furthermore, it is inferred that in BPA polycarbonates the restricted motion of the phenyl groups occurs cooperatively with the carbonyl group and that this mode of motion is the principal contributor to the dielectric and mechanical loss peaks observed near 170°K. The glass transition temperature of the dichlorotetrafluoro compound is only 5°C higher than the hexafluoro compound. Nevertheless, the reorientation of the -CF2CL groups and the phenyl groups in the dichlorotetrafluoro compound occurs 100°C higher than the corresponding motions in the hexafluoro compound.