Inverted and Amplified Circularly Polarized Luminescence Behavior Originated from Structure–Activity Regulation of Achiral Pyrene-Based Polymers in Chiral Coassemblies

Abstract

The design of excellent circularly polarized luminescence (CPL) materials with a large luminescence dissymmetry factor ( g lum ) remains a great challenge. In this paper, we chose two achiral conjugated pyrene-based main-chain polymers ( BP-1 and BP-2 ) with different substitution positions (1,6-positions of the pyrene rings for BP-1 and 2,7-positions of the pyrene rings for BP-2 ) and a chiral binaphthyl-based inducer ( S / R -D ) with a bridged alkyl chain to construct chiral coassemblies through an intermolecular chirality induction mechanism. Interestingly, after the thermal annealing treatment, the resulting coassemblies S / R -D-BP-2 could emit inverted and amplified CPL signals compared with S / R -D-BP-1 . Most significantly, the maximum | g lum | value of ( S / R -D) 0.2 -(BP-2) 0.8 in a spin-coated film was up to 0.71 (λ em = 428 nm, QY = 44.8%) at a 220 nm thickness, which was about 6-fold that of ( S / R -D) 0.1 -(BP-1) 0.9 (| g lum | = 0.12, λ em = 451 nm, QY = 37.6%). The excellent g lum value of ( S / R -D) 0.2 -(BP-2) 0.8 was due to the formation of regular and ordered helical nanofibers through the strong intermolecular π–π stacking interactions. This work provides a creative approach to tune the CPL emission amplification behaviors by chiral coassembly from achiral pyrene-based main-chain polymers.

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