Copolymerization behavior. After the proof of concept, the copolymerization behavior of POT was further investigated by determining the copolymerization ratios. DOT is up to now the most efficient thionolactone to copolymerize with styrene and acrylate with reactivity ratios at 80 °C in the case of styrene: rS = 2.0 and rDOT = 0.3 and in the case of methyl acrylate: rMA = 0.2 and rDOT = 1.6. These reactivity ratios led nevertheless to a composition drift with increasing conversion. POT was designed to be an alternative of DOT and according to the DFT calculations, we could expect a more random incorporation of the two comonomer into the polymer backbone. To validate this hypothesis, we thus measured the reactivity ratios of POT with styrene, and the bulky isobornyl acrylate (IBA) that led to high Tg acrylate that facilitates purification and handling (Figure ).