In addition to SiRMS descriptors, we calculated classical molecular descriptors usually used for QSPR studies of small molecules. For this purpose, SMILES codes of the relevant drugs and monomeric building blocks, capped with methyl groups (as performed in previous polymer QSPR studies ), were first loaded into RDKit and 3D structures were optimized via the MMFF94s force field . Subsequently, all 2D/3D molecular descriptors d implemented in mordred and PaDEL were calculated (Figure ). In order to transform these to features describing mixtures, a similar approach as previous QSPR modeling works was applied : they were weighted according to their molar ratio n within the mixture of interest. Different (nonlinear) combinatorial approaches have been proposed for using such descriptors for mixtures ; in this work we used a simple linear combination of the descriptors.