Subsequently, we evaluated the PL emission of the obtained polymers of different molecular weights (DP = 15 -100). For both linear and four-arm polymers, the prolongation of the chain length led to a significant increase of PL intensities in the aqueous aggregate state (Figure , E; Figure and), accompanied with small blue shifts (< 20 nm) of maximum emission wavelength. These results can be explained by the enhanced steric hindrance from the longer polymer segments at higher DP, preventing strong π-π stacking of the PDI scaffold. Meanwhile, a greater difference was found in the emission intensity of PDI-tetraPS compared to PDI-diPS when prolonging the polymer chain length. At their highest DP, a ~3fold higher PL intensity was observed for PDI-tetraPS than that for PDI-diPS in their aqueous aggregates (Figure ).