Additionally, the much smaller signals 2' (at 7.32 ppm), 3' (at 6.94 ppm) and 1' (at 2.48 ppm) are attributed to 4MTP, presumably formed during polymer work-up and storage (at 8.0 °C) (Figure ). The GPC traces show a clear and controlled increase of the molar masses with increasing [M]0/[I]0, even though the experimental molar masses tended to be somewhat smaller than expected (Figure ). They also show that the resulting polymers are essentially monomodal and relatively narrowly distributed, resulting in low values for Ð (Figure , supporting information, Table ). The elugram of PSar with [M]0/[I]0 = 10 significantly overlaps with the system peak and residual solvent. We also assume that the particularly low yield for PSar with DP = 10 is due to significant loss during work-up rather than due to problems with initiation/polymerization. Optimization of this work-up for the low-molar mass PSar was outside the scope of this contribution. Importantly, successful initiation with 4MTPPC was further confirmed with MALDI-ToF mass spectrometry. MALDI-ToF mass spectrometry confirms the increase of molar mass with increasing [M]0/[I]0 and also the narrow molar mass distribution (Figure ). In all cases, the mass differences (Δ m/z) between individual signal distributions reflect the molar mass of the polymer repeat unit (71.2 g/mol). In contrast to GPC, the polymer obtained from a targeted [M]0/[I]0 = 10 shows a molar mass distribution reminiscent of a