Enabling Wholly Aromatic Triphenylamine-Based Polyimides to Realize Bathochromic Emission

The development of wholly aromatic polyimides (Ar-PIs) in the field of fluorescence material has long been hindered by the charge-transfer complex (CTC) effect, typically causing weak or non-detectable fluorescence intensity. Few studies have aimed to reduce the CTC effect through molecular design, enabling Ar-PIs to exhibit blue to yellow emission in solid films with high quantum efficiency (Φ _PL). However, current complex molecular designs pose inherent limitations for further reducing the emission energy gap toward the orange-red regions. To address this issue, in this work, a series of triphenylamine (TPA)-based fluorescence diimides with various electron-donating/extended π-conjugation pendant groups are strategically designed and synthesized to probe their emissive behaviors and the corresponding Ar-PIs properties. Notably, along a series of new Ar-PIs, PI-TPE, PI-TPPA-TPE, and PI-TPPA exhibit a systematic bathochromic shift emission at 540, 598, and 608 nm, respectively, in the film state, where PI-TPPA and PI-TPPA-TPE fill up and realize the full-spectrum emission by utilizing the TPA architecture.