Nuclear magnetic resonance (NMR) spectroscopy was used to calculate monomer conversions and to analyse products. Spectra were recorded on a Bruker AVANCE III HD 500 MHz or 400 MHz NanoBay spectrometer. Samples were prepared by dissolving 5-30 mg solid sample 50-100 μL of liquid sample in 400-500 μL CDCl3 in 5 mm NMR tubes. The residual solvent signal (δ = 7.26 ppm) was used as reference. Thermal gravimetric analysis (TGA) experiments were performed on a TGA Q500 (TA Instruments, New Castle, United States). A sample of 2-5 mg was loaded in the platinum pan and heated at a heating rate of 10 °C/min from room temperature (RT) to 800 °C under nitrogen atmosphere with a flow rate of 60 mL/min. Thermal decomposition temperature is defined as the temperature at which only 95% of the original mass remains.