Solid‐state 1H → 19F/19F → 1H CP/MAS NMR study of poly(vinylidene fluoride)

Abstract

AbstractSolid‐state 1H → 19F and 19F → 1H cross‐polarization magic angle spinning (CP/MAS) NMR spectra have been investigated for a semicrystalline fluoropolymer, namely poly(vinylidene fluoride) (PVDF). The 1H → 19F CP/MAS spectra can be fitted by five Lorentzian functions, and the amorphous peaks were selectively observed by the DIVAM CP pulse sequences. Solid‐state spin‐lock experiments showed significant differences in T1ρF and T1ρH between the crystalline and amorphous domains, and the effective time constants, THF* and T1ρ*, which were estimated from the 1H → 19F CP curves, also clarify the difference in the strengths of dipolar interactions. Heteronuclear dipolar oscillation behaviour is observed in both standard CP and 1H → 19F inversion recovery CP (IRCP) experiments. The inverse 19F → 1H CP‐MAS and 1H → 19F CP‐drain MAS experiments gave complementary information to the standard 1H → 19F CP/MAS spectra in a manner reported in our previous papers for other fluoropolymers. The value of NF/NH (where N is a spin density) estimated from the CP‐drain curve is within experimental error equal to unity, which is consistent with the chemical structure. Copyright © 2001 John Wiley & Sons, Ltd.