In order to investigate the effect of increasing side chain length (rendering the system more hydrophobic) on drug loading and to check the applicability of HSPs, previously a library of 18 different POx/POzi based ABA triblock copolymers was synthesized, comprising pMeOx as A, while varying the hydrophobic B block from series of linear , branched (aliphatic POx with varying side chain lengths; C4-C9) or an aromatic side chains . The polymers with shorter side chain length (C3 and C4) appeared to be the best solubilizer for various drugs, However, no clear trend was predicted by HSPs. Thus, the main aim of the present study is to establish an effective, rapid and simple method for the rational design of drug formulations. Therefore, the goal was to develop a formulation library with high drug loading as well as the comparison of calculated HSPs, to identify if they can be used as means to predict the polymer drug compatibility in these systems. Accordingly, from the previously synthesized library, we selected the best performing polymers and tested their solubilizing capacity with a library of 21 different hydrophobic drugs. The HSPs were also estimated theoretically and experimentally to guide formulation development and to check their applicability for such systems.