To evaluate the possible CT effect brought by styrene units in PDI polymer aggregates, multiscale molecular modeling of simplified model structures was performed to study the electronic structure and transitions. Density functional theory (DFT) calculations in isolated states were first carried out on four-arm PDI oligomers containing 4 monomer units, represented as PDI-tetraSt4, PDI-tetraMMA4, and PDI-tetraBMA4. As shown in Figure , both the lowest unoccupied molecular orbitals (LUMOs) and the highest occupied molecular orbitals (HOMOs) are located at the PDI scaffold for each considered oligomer, with the energy gap calculated to be ~2.5 eV. These observations indicate that the imide-substituents did not change the isolated PDI electronic structure, which is in line with the experimental results in the diluted state (in DMF).