Excited state intramolecular proton transfer (ESIPT) is one of the distinctive photophysical processes of fluorescent compounds and polymers, which induces enhanced fluorescence with a very large Stokes shift. In this work, 6FDA/DCHM/3HPA polyimides (PIs) having bulky –CF₃ groups were synthesized, in which 3HPA is an end-group which exhibits ESIPT with enhanced green emission when irradiated by UV light at 365 nm. Introduction of bulky side chains can improve fluorescent properties via suppression of aggregation induced quenching as well as intermolecular interactions. All the 6FDA-based PI films were colorless and transparent in the visible region, and the PIs having 3HPA end-groups exhibited obvious green emission at 530 nm, when excited at 340 nm. Compared with the corresponding ODPA-based PIs which have no bulky side groups, the 6FDA-based PIs demonstrated significantly higher quantum yields in the solid state (Φ = 0.14−0.25), which is attributable to the looser aggregation structures owing to the bulky and less polarizable –CF₃ group and the absence of energy transfer to/from the non-fluorescent main chain units. Accordingly, the experimental results proved that the introduction of bulky –CF₃ groups using 6FDA moiety is a promising way to create highly fluorescent end-capped PIs.