Solid-state 1H-static, 1H-MAS, and 1H → 19F/19F → 1H CP/MAS NMR study of poly(vinyl fluoride)

Solid-state H-1 --> F-19-CP/MAS, 19F --> H-1 CP/MAS, and H-1 fast MAS NMR spectra have been investigated for a semicrystalline polymer, namely poly(vinyl fluoride) (PVF), together with its solution-state F-19 spectrum and static solid-state H-1 pulsed and broad line NMR measurements. The static H-1 pulsed NMR measurements of T-1p(H) and T-2(H) showed the two-phase (immobile and mobile) nature, and the Goldman-Shen type phase selection at 130 degreesC indicated that a measure for the lamellar size yields about 4.2 nm. Although the solid-state F-19-CP/MAS spectrum shows a featureless lineshape, the mobile region was selectively observed by a newly developed DIVAM pulse sequence. Solid-state spin-lock experiments showed significant differences in T-1p(F) and T-1p(H) between the immobile and mobile regions, and the effective time constants, T-HF(*) and T-1p(*), which were estimated from the H-1 --> F-19 CP curves, also clarify the difference in the strengths of dipolar interactions. Furthermore, the H-1 --> F-19 inversion recovery CP (IRCP) experiment was more advantageous in observing the relatively weak dipolar interactions in the mobile region. The inverse F-19 --> H-1 CP/MAS and H-1 --> F-19 CP-drain MAS experiments gave complementary information to the H-1 --> F-19 CP/MAS spectra, although spinning at 35 kHz is necessary to separate the signals between CHF and CH2 protons in the H-1 spectra. The hetero-nuclear dipolar oscillation behaviours and the effective time constants, T-HF(*) T-FH(*) and T-1p(*) determined from the H-1 --> (19) CP/MAS, CP-drain MAS, and F-19 --> H-1 CP/MAS experiments are consistent with each other. In addition, the value of N-F/N-H (N is a spin density) estimated from the CP-drain curve is equivalent to that calculated from the chemical structure. (C) 2001 Elsevier Science Ltd. All rights reserved.