The elimination of the red emission peak at 620 nm can be attributed to the interrupted anthracene-NDI charge transfer process, as the photo-induced dimerization of anthracene breaks its -conjugated structure. Consequently, the blue emission at 480 nm predominates after most of the anthracene groups have reacted, which is likely due to polystyrene/NDI or NDI/NDI interactions. A similar behavior was also observed in another NDI polymer bearing anthracene moiety -NDI-coAntMAc with anthracene monomer loading of 4.70% (PAM feed = 2.5%, Figure ).