In this study, supercritical CO 2 (scCO 2 ) 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 1 H ! 13 C 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 scCO 2 impregnation as an efficient and possibly versatile methodology to prepare polymer samples for DNP ssNMR investigations.
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