As reported previously,17 the photo-LRP mediated by organocobalt porphyrins might
undergo reversible termination mechanism. The propagation process is through monomer insertion into the cobalt−carbon bond in organocobalt porphyrins. Thus, α ends of obtained polymers should be organo groups of starting cobalt complexes, and ω ends should be cobalt porphyrins. In order to investigate the polymer structure, (TMP)Co-13CO2CD3 with analogous structure to IV was synthesized under similar conditions. It was characterized by ESI-MS, 1H NMR, and 2D NMR. Before photopolymerization, the 2D NMR spectrum gave a clear signal at −3.667 ppm, corresponding to the deuterium atoms of methyl group in (TMP)Co-13CO2CD3 (Figure 6a).