Triarylamine‐Based Wholly Aromatic Polyimide with Simultaneously Unprecedented Photoluminescence Efficiency and High Glass‐Transition Temperature

Abstract

The weak photoluminescence (PL) of wholly aromatic polyimide (Ar‐PI) is generally associated with the strong charge‐transfer complex effect in both solution and solid states. Research has focused on structural designs promoting the PL behavior, but Ar‐PI PL remains a challenge in the solid state. Herein, a twisted conformation is incorporated into a triphenylamine‐based polyimide backbone to obtain a series of Ar‐PIs with extremely high PL quantum efficiency (ΦPL) in solution and even film states. PI3M‐4M exhibits the highest ΦPL of up to 61% in the film state, which is considerably superior to the values for reported Ar‐PIs. PI3M‐4M is also the first Ar‐PI to simultaneously demonstrate an unprecedented ΦPL with a remarkable glass‐transition temperature Tg of 470 °C.

Fluorescent Polyimide Films with Covalently Incorporated Perylenediimide

“…The FLQEs of the films are quite high: 5.8% for PDI MBMCHA -PI, 25.1% for PDI MBCHA -PI, 5.7% for PDI BAMN -PI, 14.5% for PDI IPDA -PI, and 22.8% for PDI CHAM -PI in the solid state (Table ). All the films are still quite emissive, although the FLQEs are lower compared to the polymers reported from the previous pioneering works. − The spectral shapes and the maximum FL wavelength are almost identical to those measured in the dilute solution, although the FLQEs are lower than those in the solution (Figure b and Table ). This means that PDI exhibits monomer FL without excimer formation even in films.…”

“…Various efforts have been made to impart FL to PIs, but at present, visible-light FL is only observed in structures based on a specific transition state such as CT, excited state intramolecular proton transfer, − and aggregation . Alternatively, a method for synthesizing new fluorophore monomers and applying them to PI production has been proposed. − As an example in some pioneering works, partially aromatic polyimides prepared from aggregation-induced emission-active diamines showed extremely high quantum efficiencies of up to 89%. , Also, aromatic polyimides derived from electron-donating triarylamine-based dianhydrides with bulky pendant groups showed high efficiencies of up to 61% with a high glass transition temperature of 470 °C. − Since such new monomers may make the synthetic procedure cumbersome, however, our study sought to find a more universal method that uses commercial compounds as all the starting materials.…”