1H and 13C NMR: 
Spectra were analysed using Mestrelab MNova 11.0 software where spectra were baseline corrected and line broadening used to allow accurate integration of peak area. 

GPC: 
Chromatograms were analysed in Agilent GPC/SEC software to extract Mn and PDI values.

UV-vis: 
The presence of the SC12 end group can be monitored by the peak at 310 nm in UV-vis spectra. To estimate the percentage end group conversion, resultant spectra were normalised by the styrenic absorbance peak at 260 nm, the concentration of which is unchanged by end group conversion. This can then be compared to the reference spectrum for a solution of SMA2000, which has no thiocarbonylthio (SC12) end groups.