The observed chain length-dependent variation of emission spectra is a result of the varying TSCT degree with different D-A (e.g., pyrene-NDI) distances, which increase with the growth of polymer chain . Notably, despite a MW of 13,000 g mol -1 , the TSCT emission at ~630 nm in NDI-PS-Py (Figure ) is still clearly visible, indicating a strong interaction between pyrene and NDI in the end-group functionalized polymers. Consequently, depending on the π-conjugation degree of the introduced end group, broad emission color tunability with PL spectra ranging from 400 to 800 nm was again achieved (Figure ). In addition, various fluorescence lifetimes of distinct polymers were observed (Figure ) in tandem with the redshifted tails on the absorption spectra (Figure ).