High‐Efficiency Photoluminescence Wholly Aromatic Triarylamine‐based Polyimide Nanofiber with Aggregation‐Induced Emission Enhancement

Abstract

Novel AIE‐active, high Tg (up to 420 °C), and solution‐processable wholly aromatic polyimides with triarylamine chromophores are synthesized and fabricated into highly efficient photoluminescence (PL) nanofibers by an electrospinning method. The PL intensity of polymer solutions is induced by aggregation in poor solvents, and they could be fabricated into solid films with high PL quantum yields of up to 22%, demonstrating their aggregation‐induced emission feature. Moreover, the electrospun nanofibers have the highest PL quantum yield of 26% among aromatic polyimides, suggesting their great potential for high‐performance optoelectronic applications.

Quantum Efficiency Increasing of a Pristine Polymer by Curbing Picosecond Self-Trapping via Segmental Stretching

“…34 The aggregates may also cause reduced torsion freedom in polymers of certain chemical structures to increase the fluorescence (the aggregation-induced emissions, AIE). 30,32,33 Therefore, in the event of mechanical stretching of a pristine CP system, a complicated fluorescence behavior may arise, which would be strongly influenced by AIE, AIQ, enhancement by backbone stretching, and quenching from the newly created ill-packed regions of extensive chain twisting adjacent to aggregates that may nearly unscathed under the applied deformations. 17,23,31 Clearly, sufficiently large deformations that can effectively unravel the aggregates are necessary to have the backbone stretching effects truly emerged in the pristine systems.…”

“…Low quantum efficiencies (QEs) have long been the major hurdle for conjugated polymers (CPs) competing in the field of optoelectronics in spite of their edges in the cost, ease of processing, application flexibility, and mechanical durability. − Recent reports have revealed that increased backbone stresses via mechanical stretching can lead to dramatically enhanced QEs of the CPs in the dispersed solid states. − However, the mechanical effects have been unclear in the pristine counterparts, the prevalent form in applications for CPs, casting doubts on the validity and implications of the mechanical effects. Hence, it is highly intriguing to investigate the mechanical effects thoroughly in the pristine CPs and at the same time, taking advantage of the high chromophore densities in the pristine films, to explore the photonic behavior in the ultrafast time frame commensurate to the electron–phonon coupling that may affect the QE behavior of the long-chain molecules. − …”

Synthesis and Characterization of White-Light Luminescent End-Capped Polyimides Based on FRET and Excited State Intramolecular Proton Transfer

“…To suppress the CT and LE(n−π*) transitions and enhance the LE(π−π*) transitions between the S 0 and S 1 states, we have developed a series of highly fluorescent PIs with high Φ values by combining dianhydrides with high electron-accepting ability, whose HOMO-LUMO transitions are LE(π−π*), and alicyclic diamines with low electrondonating ability [15,[20][21][22][23][24][25][26][27][28][29]. With other methods, highly fluorescent fully aromatic PIs have been developed by introducing aggregation-induced emission (AIE)-active bulky moieties, such as modified triarylamine [30,31] or tetraphenylethylene structures [32], in their main or side chains.…”

Investigation of thermal and fluorescent properties of benzoxazole-linked triphenylamine-based co-polyimides

“…55 The low emission quantum yields of 1-PMDA and 1-BTDA are mainly due to the polymeric chain rigidity which undergoes active rotation and vibrations in solution, and it might be due to interconversion from highest emissive excited state to lowest emissive state, thus resulting in fast non-radiative relaxations and lesser emissions. 56 Luminescence properties were studied by preparing the thin films of co-polyimides. The luminescence values were ranged from 0.29 Cd m −2 to 0.34 Cd m −2 .…”