Amplified Circularly Polarized Electroluminescence Behavior Triggered by Helical Nanofibers from Chiral Co-assembly Polymers.

Abstract

Two chiral binaphthyl polymers (R/S-P1 and R/S-P2) with different dihedral angles of the binaphthyl moiety were chosen as chiral inducers to construct chiral co-assemblies with an achiral pyrene-naphthalimide dye (NPy) and then acted as the emitting layer (EML) of circularly polarized electroluminescence (CP-EL) devices. The anchored dihedral angle of R/S-P2 not only exhibited the enhanced chirality signal, but also had a strong chirality-inducing effect on the achiral NPy dye in the chiral co-assembly (R/S-P2)0.6 -(NPy)0.4 . After annealing at 120 °C, the CPL signal (|gem |) of ordered helical nano-fibers (R/S-P2)0.6 -(NPy)0.4 was amplified to 5.6×10-2 , which was about 6-fold larger than that of (R/S-P1)0.6 -(NPy)0.4 . The amplified gem value of (R/S-P2)0.6 -(NPy)0.4 was due to the formation of a helical co-assembly through the strong π-π stacking interaction between the R/S-P2 and the achiral NPy. This kind of ordered helical nano-fibers (R/S-P2)0.6 -(NPy)0.4 acted as the EML of CP-OLEDs, and achieved an excellent CP-EL performance (|gEL |=4.8×10-2 ).