Porous Polymers for Generating Slow Relaxing Hyperpolarization under Benchtop-DNP conditions.

Dissolution dynamic nuclear polarization (dDNP) is a hyperpolarization method providing orders-of-magnitude sensitivity boost for liquid state nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) experiments. We recently introduced a new hyperpolarization strategy based on DNP at 1 T and 77 K (instead of 7 T and 1.2 K) and demonstrated two-orders-of-magnitude signal enhancements with a compact and affordable benchtop instrumentation, designed to enable repeated hyperpolarization cycles for multi-scan NMR experiments. However, as in conventional dDNP, the required presence of paramagnetic polarizing agents for DNP is a major roadblock to melt the sample without dilution. The introduction of hyperpolarizing porous polymer (HYPOP) matrices achieved the paradoxical goal of generating fast polarization while preserving long relaxation times within the matrix. This breakthrough enabled the generation of transportable hyperpolarization for dDNP. In this study, we evaluate HYPOP under benchtop DNP conditions, demonstrating their ability to minimize paramagnetic relaxation effects before and after dilution-free melting, a key step in our benchtop DNP workflow. We report 1H signal enhancement factors exceeding 45, and 13C polarization lifetimes over 50 seconds at 77 K, and 18 seconds at 298 K, while the sample remains impregnated in the matrix. This represents a key milestone toward non-destructive melt DNP for replenishable hyperpolarized solution-state NMR.