Nuclear magnetic resonance spectroscopy of Vinylidenefluoride polymers.

Abstract

High-resolution solid- and solution state NMR techniques have been applied in the study of a Semi crystalline fluoropolymer Poly(vinylidienfluoride) (PVDF) and a vinylidienfluoride telomer. The application of standard solution-state experiments with high power decoupling and two-dimensional techniques has provided a greater understanding of the structure of these two fluoropolymers. Specifically, Cosy and Tocsy experiments gave information on signals normally related to end groups and to previously unidentified structures, which suggest the presence of at least a second major structure. 19F solid-state Magic Angle spinning Nuclear Magnetic Resonance (MAs- NMR) using relaxation filters in pulse sequences, has revealed fundamental differences relating to morphology and structure. The location of reverse units in the amorphous and crystalline domains is investigated by fluorine Tip filtered Radio Frequency Driven Recoupling (RFDR) and spin-diffusion experiments. These experiments proved that the reverse units are dominant in the amorphous phase, yet could have association with rigid species. Furthermore, signals generally associated with crystalline domains are not homogenie in character. The presence of a highly mobile species was detected and investigated using the delayed acquisition technique and T2 measurements. This showed the possibility of end-group signal in the spectral region normally associated with reverse groups. Furthermore, proton Tip measurements of nascent and annealed PVDF, recorded at variable temperature are related to molecular motion and debated with respect to the effect of spin diffusion on populations. The relationship between thermal events and thermal history of PVDF and its effect on molecular motion is debated.