Successful incorporation of the drug monomer is crucial for future applications. We therefore investigate the incorporation efficiency of the prodrug monomer 2, or in other words the drugloading of P1 -P6. The highest drug loading is to be expected for P1 with its high 1:1 ratio of prodrug monomer to 2,5-diiodo-N-methylimidazole co-monomer, while the lowest drug amount is expected for P6. After synthesis, the particles can be easily separated from the synthesis medium by centrifugation, allowing us to analyze the soluble fraction of monomers in the supernatant by LC-MS. Specifically, we determine the peak area of compounds 2 and the comonomer 2,5-diiodo-N-methylimidazole before synthesis and in the supernatant after synthesis (see Figure , a more detailed description of the method can be found in the Supporting Information: Drug Loading, see Tables and and Equations S1 -S7). Comparing the two monomer peaks allows us to determine their ratio, as well as the molar fraction of the loaded drug (DLn) and the mass fraction of drug loading (DLm) (see Table ). As discussed above, a small fraction of prodrug 2 may decompose during polymerization. Therefore, we calculate the drug loading efficiency as a range between a maximum value, where no degradation is considered and a minimum value, where the degradation of the drug monomer after 3 h in the reagent solution is considered (see discussion above and Table ). We assume that the real level drug loading will be closer to the given maximal drug loading, because as soon as the drug is incorporated into the backbone and phase separated from the dissolved state, the likeliness of