β Scribed by Wilson, Charles W.
No coin nor oath required. For personal study only.
The effects of molecular magnetic anisotropy upon the broadline NMR spectrum of a bulk polymer have been recognized and measured for the first time. The F^19^ NMR absorption spectra in polytetrafluoroethylen (PTFE) show a lineβshape asymmetry over a broad range of temperatures which can be explained by the magnetic anisotropy of CβF bonds. Nuclear magnetic resonance studies of PTFE samples whose crystalline regions are aligned by cold drawing have made possible an estimate of the anisotropy of CβF bonds in this material: ΞΟ, the magnetic anisotropy of the screening constant, is found to be 171 Β± 15 ppm; the screening of each F^19^ nucleus is paramagnetic, being maximum when the direction of its CβF bond is perpendicular to the large static magnetic field and minimum (probably zero) when parallel. Static magnetic susceptibility measurements of PTFE show the predicted diamagnetism, and only a small (<5%) static magnetic anisotropy of the molecular crystals is found.
π SIMILAR VOLUMES
Drpolrrr magnetic iicld cffccts ha\c been dcteckd m rhe NMR spectn oieoroncnc end mcrhylpyropheophorbtde UI hquld solu11on. Thcsc cficcls arose from rhc par1131 molecular abgnment mduccd by the magnelic field. Both 'H-\*H uud \*JC\_ 'H couplinp 113~ been dclcctcd Tar both compounds the anisotropy II
Becently mrrh attention has been paid to the bond or rubstituent diamagnetic anisotropy effect on proton nmr chemical shift(2). In estimating the long-ranBe diamagwtic anisotropy effect, McConnell88 equation( ), bani = CAx(1 -3cor20)3/ 3x3 , has frequently been used and scassttis a satisfactory agre