HIGH-RESOLUTION C-13 NUCLEAR MAGNETIC-RESONANCE OF SOLID POLY(OXYMETHYLENE)

13C spectra and relaxation times were determined for poly(oxymethylene) at 45 MHz with proton-decoupled magic-angle-spinning NMR with and without cross-polarization. The results indicate the coexistence of two phases: a crystalline phase with short T1p and long T1 and an amorphous phase with a longer Tlp and a shorter T1. These results are consistent with crystallinity measurements on the same samples by X-ray diffraction. The crystalline T1p, which is not thought to be a pure spin-lattice relaxation parameter but is also determined by spin-spin interaction, depends on the spinning frequency. At high spinning frequency (>~5 kHz), the line width (at magic-angle-spinning conditions) increases with an increase in the spinning frequency. © 1979, American Chemical Society. All rights reserved.