13C Solid-State NMR of the Mobile Phase of Poly(vinylidene fluoride)

The solid-state C-13 spectra of poly(vinylidene fluoride) (PVDF) acquired by direct polarization (DP) with and without simultaneous F-19 and H-1 decoupling, under moderate sample spinning conditions, are compared to the spectra obtained using direct polarization followed by a short Hahn echo. We show that by using an appropriate combination of saturation and dephasing conditions high-resolution solid-state C-13 NMR spectra of the amorphous domain can be obtained. These spectra allow for a complete assignment of the solid-state C-13 NMR spectra of the amorphous phase of PVDF, and we propose a simple methodology to obtain high-resolution solid-state C-13 NMR spectra of high molecular weight polymers. Furthermore, these spectra lead to the conclusion that differential line broadening is occurring in the multiplet structure of the signals present in the coupled spectra. This can be attributed to relaxation interference effects and further reduces the line width in the coupled spectra, allowing for the dramatically improved resolution. In addition, this explains the loss of resolution when decoupling is applied during the acquisition of the solid-state C-13 spectra of PVDF.