Avance III 500 NMR spectrometer with a Bruker HR MAS probe using a ZrO2 rotor (4 mm outer diameter) with a PTFE insert (50 μL insert volume). For the measurements, the insert was filled with the dried co-networks (~2 mg). After addition of CDCl3 (~50 μL) and a swelling time of 30 minutes, the spectra were recorded at 30 °C with a rotation frequency (νr) of 4650 Hz. Under these conditions, minimal overlap of signals and spinning sidebands was observed. The conversion was determined from the integral intensities of a signal of the reacted benzoxazinone group (H7' of CN;