Triple Resonance ~1H/~(13)C/~(19)F Multidimensional Solution NMR of Fluoropolymers: Experimental Aspects

摘要

In the work the use of 1D and multidimensional ~1H/~(13)C/~(19)F triple resonance 750 MHz NMR techniques for characterizing fluoropolymers are illustrated. When characterizing fluoropolymers, it is possible to take advantage of the large spectral dispersion, the high natural abundance, and the large gyromagnetic ratios of the ~1H and ~(19)F nuclei. However, the enormous ~(19)F chemical shift range creates some practical difficulties. The indirect detection pulse sequences had to be modified to introduce composite pulses on the transmitter channel to reduce offset problems, and WURST adiabatic decoupling was used to reduce problems associated with decoupling over the large frequency range. Vinylidene fluoride - hexafluoropropene copolymer was studied. High field, ~1H/~(13)C/~(19)F triple resonance, and multidimensional NMR provides enormous spectral simplification, permitting the extraction of structural information. Experimental conditions for collecting high quality spectra are outlined and complete resonance assignments for the most abundant structures in the polymer are given.