Redox-active polymers such as macromolecular nitroxide radicals have been studied as electrode materials for organic batteries and electronics. Polymer-solvent interactions are essential to processing and device performance, but macromolecular nitroxide radical-solvent interactions are currently not well described. In this work, the Hildebrand and Hansen solubility parameters of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA), oxidized PTMA (PTMA(+)), and PTMA's precursor (PTMPM) are determined using both experimental and group contribution methods for the first time. This work indicates that the hydrogen-bonding Hansen solubility parameter (delta(h)) and the solubility sphere radii (R) provide the best prediction of the macromolecular radical's interaction with solvents. From these solubility parameters, the group contribution values for the nitroxide and oxoammonium cation were then calculated. It is shown that this information allows for the prediction of polymer-solvent interactions for other nitroxide-based macromolecular radicals. Finally, the discovered solubility parameters are used to predict PTMA electrode formulations for batteries that outperform controls.