Rational design of soluble intrinsic black polyimide containing tetraphenylcyclopentadienone-based chromophore

Abstract

Black polyimide shows growing demand in optoelectronic apparatus instead of yellow transparent polyimide. However, the most used black polyimide filled with carbon black suffers from the deterioration of electrical and mechanical properties. In this work, a soluble intrinsically black polyimide (TPCPPPPI) with exceptional electrical and mechanical performances was designed and prepared by the polycondensation of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and a new diamine (TPCPPPDA), which bears tetraphenylcyclopentadienone (TPCP) linked with four benzene rings. Introduction of TPCP-based chromophore into PI molecular chain greatly red-shifted the absorption scope, thus achieving absorption of whole visible light. The resulted TPCPPPPI exhibited highly opaque and black color, with a cut-off wavelength (λcut) up to 698 nm and CIE (Commission Internationale de l'Eclairage) color parameter L* low to 1.41. Simulation calculation suggested that the highly black color of TPCPPPPI was primarily ascribed to the electrons transitions from the highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) in the chromophore-bearing diamines, in which the charges chiefly migrated from the 2,5-position aryl groups to the middle cyclopentadienone. Meanwhile, TPCPPPPI exhibited exceptional solubility, mechanical and electric performance. The intrinsically black PI accompanying with exceptional performance and organosoluble feature has attractive potential application in optoelectronic field.