Dynamic Nuclear Polarization with Conductive Polymers

The low sensitivity of liquid-state nuclear magnetic resonance (NMR) can be overcome by hyperpolarizing nuclear spins by dissolution dynamic nuclear polarization (dDNP). It consists of transferring the near-unity polarization of unpaired electron spins of stable radicals to the nuclear spins of interest at liquid helium temperatures, below 2 K, before melting the sample in view of hyperpolarized liquid-state magnetic resonance experiments. Reaching such a temperature is challenging and requires complex instrumentation, which impedes the deployment of dDNP. Here, we propose organic conductive polymers such as polyaniline (PANI) as a new class of polarizing matrices and report 1H polarizations of up to 5%. We also show that 13C spins of a host solution impregnated in porous conductive polymers can be hyperpolarized by relayed DNP. Such conductive polymers, if synthesized as chiral, can have their electron spins hyperpolarized close to unity without the need for either low temperatures or high magnetic fields, but by simply flowing electrical current through them, which is highly promising. Our results show the feasibility of solid-state DNP in conductive polymers and pave the way toward DNP from hyperpolarized electrons in their chiral form in the future.