In CHCl3, monomer consumption was fastest and a markedly higher proportion of cyclic dimer was observed compared to the reactions carried out in MeCN and PhCN. MALDI-ToF mass spectrometry of the product obtained from CHCl3 confirmed low molar mass. Unfortunately, the desired product (MTP-initiated PSar) and the macrocyclic PSar have an identical m/z ratio and virtually the same isotope pattern, and therefore we cannot distinguish the two by mass spectrometry (supporting information, Figure and). The signal attributed to PSar initiated with 4MTP was observed. However, the presence of low molecular weights cyclic polypeptoids or dimers could not be determined. Interestingly, the obtained signals could also be assigned to oxidized or partly oxidized PSar initiated with 4MTP even though any oxidation was performed. In addition, MALDI-ToF MS data corroborate the molar mass values obtained by GPC (supporting information, Figure )