Chapter 22. Structural Investigations of Polymer Materials by Dynamic Nuclear Polarisation Solid-state NMR

Solid-state nuclear magnetic resonance (SSNMR) has established itself as an essential structural elucidation technique in polymer science because it can non-destructively provide unique molecular-level information with atomic resolution on complex macromolecular materials, especially when combined with complementary techniques such as scattering and computer simulation. The Achilles’ heel of NMR, however, is its low sensitivity due to the weak nuclear spin polarisation at thermal equilibrium, even at very high magnetic fields. One intriguing way to enhance NMR sensitivity is dynamic nuclear polarisation (DNP), which relies on the microwave-driven transfer of thermal electron spin polarisation to nuclei. DNP is attracting scientific attention owing to the availability of both high-power/high-frequency microwave sources and efficient DNP polarising agents (i.e., paramagnetic species used for doping diamagnetic samples to provide the source of electron polarisation for DNP). At moderately high magnetic fields (∼10 T), large DNP signal enhancements can now be readily obtained, which has led to unprecedented SSNMR applications. In this review, we describe the requirements for high-field DNP SSNMR and provide examples of its use for the structural analysis of organic polymer materials, so as to highlight its advantages and (current) limitations for the field.