Aggregated clusters with 5 molecules of PDI-tetraSt8 or PDI-tetraMMA8 bearing four symmetry chains were considered in DMF/H2O (5/95, v/v). As shown in Figure , B, for PDI-tetraSt8, the styrenic groups sit over the face of the PDI scaffold via molecular rotation. However, this was not observed for the conformation of PDI-tetraMMA8, and one side of the PDI scaffold remains fairly solvent exposed. The more favorable bending of styrenic groups towards PDI could be due to the weak electron-donating ability of phenyl groups. These different conformations led to a significant difference in the calculated geometry of the aggregates of five oligomers. As shown in Figure , B (bottom), no co-facial stacked PDI scaffolds were found in PDI-tetraSt8 aggregates. Instead, they remained separated by the styrenic units. In contrast, for PDI-tetraMMA8 aggregates, a dimer and a trimer of PDI H-aggregates were formed (yellow circles in Figure , B, bottom right). Altogether, these results suggest that the quenching via H-aggregation is prone to occur in PDI-tetraPMMA but not in PDI-tetraPS. Therefore, the key role of a weak TSCT induced by styrenic units in the distortion of PDI stacking structure was revealed, which facilitating the strong aggregate emission of PDI-tetraPS in solid state.