Fluorine-19 solid-state NMR investigation of regiodefective semicrystalline α-poly(vinylidenefluoride)

Solid-state 19F NMR has been applied to poly(vinylidenefluoride) to investigate, inter alia, the location of the reverse units. The application of relaxation filters in pulse sequences revealed fundamental differences relating to the domain structure of PVDF. A T1ρ(F) spin-lock experiment gave a spectrum of the crystalline phase along with some intensity from signals associated with reverse units. The proximity of reverse units to the amorphous and crystalline domains was further investigated by T1ρ(F)-filtered radio frequency driven recoupling (RFDR) and spin-diffusion experiments. The results showed the majority of reverse units to be relatively mobile (i.e. amorphous). However, weak RFDR cross-peaks were detected which suggest the presence of some reverse units in relatively rigid domains. A signal arising from a highly mobile site was detected at δF=−115 ppm by a delayed acquisition experiment and is tentatively assigned to –CH2CF2H end-groups.