Fluorine-19 NMR of Solids Containing Both Fluorine and Hydrogen

1H‐19F REDOR‐filtered NMR spin diffusion measurements of domain size in heterogeneous polymers

“…The different 19 F assignments were made using a crystalline filtering experiment (see Supporting Information) and match previous literature assignments. [33] We argue that for this blend these NMR spin diffusion experiments are probing the morphology of a mixed phase, and that for this polymer blend large PVDF crystallites are not present. The characteristic 19 F resonances associated with the formation of the β form PVDF crystallites were not observed except for blends where clear μm phase separation is seen in the SEM (additional discussion in Supporting Information).…”

“…PVDF exists in a mixture of amorphous and crystalline phases, which manifest different chemical shifts, complicating what might otherwise be expected to be a simple spectrum. The different 19 F assignments were made using a crystalline filtering experiment (see Supporting Information) and match previous literature assignments . We argue that for this blend these NMR spin diffusion experiments are probing the morphology of a mixed phase, and that for this polymer blend large PVDF crystallites are not present.…”

“…[52] Heteronuclear dipole coupling also contributes the 1 H linewidths, but the effects of moderate MAS are expected to largely suppress those interactions (see Figure S5). [33,52] For the same reasons, 19 F effects on the 1 H spin diffusion are not expected to make a large contribution. It is possible to incorporate 19 F decoupling during the spin diffusion period (Figure 1) if these heteronuclear contributions become significant, but 19 F decoupling was not incorporated in the current example.…”

“…For samples with sufficient 1 H NMR chemical shift resolution, variants of CRAMPS‐filtered sequences have been used. Double quantum‐filtered, dipolar‐filtered, and T 1ρ ‐filtered sequences exploit homonuclear dipolar couplings to select domains through the creation of multiple quantum coherences or through differences in the transverse relaxation dynamics, while 2D WISE (wideline separation) experiments rely on 1 H‐ 13 C CP for detecting the spin diffusion process . Sequences incorporating heteronuclear dephasing methods include the HARDSHIP sequence, along with the more recent 1 H‐ 13 C Lee‐Goldburg CP and 1 H‐ 13 C rotational echo double resonance (REDOR) “hole‐burning” NMR experiments to measure spin‐diffusion coefficients .…”

Quantitation of Crystalline Material within a Liquid Vehicle using 1H/19F CP/MAS NMR

“…One of the disadvantage of conventional 19 F ssNMR and its use in semi‐solid and liquid formulations is the inability to filter out mobile or dissolved API. A simple NMR method for removing signal from mobile components is 1 H/ 19 F CP/MAS 10,11. When combined with fast spinning and 1 H decoupling, this method yields well resolved 19 F peaks resulting uniquely from solid API.…”