High-resolution in-situ photo-irradiation MAS NMR: Application to the UV-polymerization of n-butyl acrylate

Light plays a pivotal role in many solid-state materials technologies. Solid-state nuclear magnetic resonance (NMR) is a key tool for characterizing atomic-scale structure and dynamics in solid materials, but requisite magic angle spinning (MAS) of the sample-containing rotors limit the measurement of these systems in their irradiated states. Here we report on a bespoke methodology for performing solid-state NMR of a sample irradiated with visible/ultraviolet (vis/UV) light, while undergoing MAS at frequencies ≤ 15 kHz. A fiber optic insert guides vis/UV light to the spinning NMR rotor, where a glass end cap and dispersion rod acts to illuminate the sample inside the rotor. This methodology was used to follow the photopolymerization reaction of n-butyl acrylate, providing well-resolved 1H and 13C NMR assignments of the formation of a semi-solid polymer gel.