Regulating Circularly Polarized Luminescent Behavior of Luminescent Liquid Crystalline Polymers through Resonance Energy Transfer

Circularly polarized luminescent materials show significant application in display devices, optical instruments, bionic fields, etc. In this work, we design and prepare a chiral luminescent liquid crystalline polymer, namely, poly(4,4',4″-tricholesterylformate-oxytetraphenylethylene-methyl acrylic acid ester) (P1). Polarizing optical microscopy (POM) and X-ray diffraction (XRD) results indicate that this polymer forms a hexagonal columnar phase. Circularly polarized luminescence (CPL) experiment shows that no CPL signal is observed for the polymer in the bulk, but the polymer mixed with a small amount of 4-cyano-4′-pentylbiphenyl (5CB) (P1@5CB) presents a strong CPL signal with a luminescence asymmetry factor (glum) of +0.18. Further, Förster resonance energy transfer (FRET) is adopted to regulate the CPL using P1 as energy/chiral donors and the achiral long-wavelength Nile red (NR) dyes as acceptors. The resultant compound shows a bathochromically shifted emission by up to 160 nm compared with P1@5CB and also emits an efficient CPL with a glum of +0.20. This result demonstrates that the controllable regulation of efficient CPL with an efficient glum is realized through nonradiative resonance energy transfer and chiral transfer.