Le, Dao, Amélie Frison, Yasmine Masmoudi, Abir Bouledjouidja, Pierre Thureau, Giulia Mollica, Elisabeth Badens, Fabio Ziarelli, and Stéphane Viel. “Supercritical CO2 Impregnation Process Applied to Polymer Samples Preparation for Dynamic Nuclear Polarization Solid‐state NMR.” Magnetic Resonance in Chemistry, September 7, 2022, mrc.5307.
In this study, supercritical CO2 (scCO2) was used to impregnate polymers with paramagnetic polarizing agents to prepare samples for dynamic nuclear polarization (DNP) solid-state NMR (ssNMR) experiments. As a proof of concept, we impregnated polystyrene samples with bTbK, which stands for bis-TEMPObisketal where TEMPO is 2,2,6,6-tetra-methylpiperindin-1-oxyl. Substantial DNP signal enhancements could be measured on DNP-enhanced 1H ! 13C cross-polarization (CP) magic-angle spinning (MAS) spectra recorded at 9.4 T and 100 K, reaching a maximum value of 8 in the most favorable case, which appeared comparable or even higher than what is typically obtained on similar systems for former sample preparation methods. These results highlight the potential of scCO2 impregnation as an efficient and possibly versatile methodology to prepare polymer samples for DNP ssNMR investigations.