Tetraphenylethylene-Based Wholly Aromatic Polyimides with Enhanced Photoluminescence Efficiency

High Resolution Image Download MS PowerPoint Slide Wholly aromatic polyimides (PIs) are promising candidates for next-generation optoelectronic materials owing to their excellent comprehensive properties. However, the strong charge-transfer (CT) interactions present in both solution and solid states typically result in poor photoluminescence (PL) efficiency, posing a significant limitation for conventional wholly aromatic PIs for optoelectronic applications. Tetraphenylethylene ( TPE ), a well-established fluorophore, is well known for its straightforward synthesis, versatile functionalization capability, and high fluorescence quantum yield ( Φ PL ) even when decorated with various substituents. Thus, incorporating TPE fluorophore into the PI backbone presents a promising strategy to develop photoluminescent PIs and overcome the inherent drawbacks of traditional conjugated polymers. Herein, TPE -diamines with trans - and cis -configurations were synthesized and subsequently polymerized with 6FDA or BPADA dianhydrides to introduce TPE into the PI main chains ( MC-TPE-PI s). However, the resulting MC-TPE-PI s exhibited negligible Φ PL, failing to deliver the anticipated emission properties. To address this limitation, a carboxyl-functionalized TPE derivative ( TPE-COOH ) was prepared and grafted as a side-chain substituent onto the PI backbone via esterification ( SC-TPE-PI s). By tuning the flexibility and electronic effects of the dianhydrides, a series of SC-TPE-PI thin films with varying TPE contents were obtained. Among them, the highest Φ PL reached 13.7%, with a tensile strength of 83.3 MPa, a tensile modulus of 1.78 GPa, a glass transition temperature of 203.1 °C, and a thermal decomposition temperature of 377 °C at 5% weight loss, demonstrating their potential as luminescent polymers for optoelectronic applications.