Enabling robust blue circularly polarized organic afterglow through self-confining isolated chiral chromophore

Creating circularly polarized organic afterglow system with elevated triplet energy levels, suppressed non-radiative transitions, and effective chirality, which are three critical prerequisites for achieving blue circularly polarized afterglow, has posed a formidable challenge. Herein, a straightforward approach is unveiled to attain blue circularly polarized afterglow materials by covalently self-confining isolated chiral chromophore within polymer matrix. The formation of robust hydrogen bonds within the polymer matrix confers a distinctly isolated and stabilized molecular state of chiral chromophores, endowing a blue emission band at 414 nm, lifetime of 3.0 s, and luminescent dissymmetry factor of ~ 10−2. Utilizing the synergistic afterglow and chirality energy transfer, full-color circularly polarized afterglow systems are endowed by doping colorful fluorescent molecules into designed blue polymers, empowering versatile applications. This work paves the way for the streamlined design of blue circularly polarized afterglow materials, expanding the horizons of circularly polarized afterglow materials into various domains.


Measurements:
The nuclear magnetic resonance (NMR) spectra were measured on a Bruker Ultra Shield Plus 400 MHz NMR instrument using tetramethylsilane (TMS) as the reference standard and deuterated chloroform (CDCl3), deuterated dimethyl sulfoxide (DMSO-d6), and deuterated water (D2O) as solvents.The chemical shifts (δ) are in ppm, the coupling constant (J) is in Hz, and the fractional peaks used are identified as: s (single peak), d (double peak), and m (multiple peak).The molecular weights of the polymers were characterized by aqueous gel permeation chromatography (GPC) with a mobile phase of 0.1 mol/L sodium nitrate and a flow rate of 0.7 mL min -1 .Powder Xray diffraction (XRD) was measured on a Bruker D8 Advance diffractometer with Cu Kα (λ = 1.5418Å) radiation at room temperature.Ultraviolet/Visible (UV/Vis) absorption spectra were characterized on a Jasco V-750 spectrophotometer.Steady-state photoluminescence (SSPL) spectra, delayed PL spectra (delay time 10 ms), fluorescence/phosphorescence lifetime decay curves, timeresolved emission spectra (TRES) and absolute photoluminescence quantum efficiency (PLQY) were conducted on an Edinburgh FLS980 spectrometer.For the fluorescence lifetime test, a picosecond pulsed laser (EPLED-295, wavelength: 295 nm, pulse width: 833.7 ps) was used; for the PLQY test, an integrating sphere was used in the Edinburgh FLS980 instruments, and the wavelength-dependent sensitivity of the detector has been calibrated automatically by Edinburgh instruments during PLQY measurement.Excitation-delayed PL spectra were characterized with a Hitachi F-4700 spectrometer (delay time: 25 ms).Photographs were taken with a Nikon D7100 camera.Chiral high performance liquid chromatography (HPLC) measurements were performed on Shimadzu LC-20AT using CHIRALCEL OJ-H column and methanol as mobile phase.The circular dichroism (CD) spectra were measured on a Chirascan V100 CD spectrometer.The transmittance mode (180 degrees) with 'Low' sensitivity was used to perform the CD spectra measurement.The scan speed was set as 200 nm/min with 1 nm resolution and a response time of 1.0 s.Circularly polarized luminescence (CPL) spectra were measured with a JASCO CPL-300 spectrometer.Wideangle X-ray scattering patterns were performed using the Xeuss 2.0 (Xenocs, France) with an incident X-ray Cu-K beam (λ = 1.54189Å).
The lifetimes (τ) of the luminescence were obtained by fitting the decay curve with a multiexponential decay function of i i () Where Bi and τi represent the amplitudes and lifetimes of the individual components for multiexponential decay profiles, respectively.
The average lifetime was calculated by the function of where φi is the amplitude fraction.
To get the intensity-averaged lifetime (τint), the φi int is defined by the function of τint is achieved by the function of To get the amplitude averaged lifetime (τamp) which was used for the analyses of SACET process, the φi amp is defined by the function of: τamp is achieved by the function of: Synthesis of R/S-COOCz: Carbazole (3 g, 0.018 mol) and sodium hydride (NaH, 0.518 g, 0.022 mol) were placed into a 250 mL double-necked flask under an argon atmosphere, then 25 mL of tetrahydrofuran (THF) was added under an ice water bath and the mixture was stirred for 1 h at room temperature.Subsequently, methyl S/R -2-chloropropionate (2.4 mL, 0.022 mol) was rapidly injected into the reaction flask and stirred for 12 h at room temperature.After the reaction, 20 mL deionized water was added to the resulting solution and the mixture was extracted with dichloromethane (DCM) for three times (200 mL).The organic layer was collected and dried with anhydrous sodium sulfate.After filtration and solvent evaporation, the given residue was purified through silica gel column chromatography using DCM/ petroleum ether (PE) (V/V: 1/1) as eluent, and white solid of R/S-COOCz was obtained.

S-COOCz
After the mixture was cooled down, the organic solvent was evaporated.Subsequently, acidification with concentrated hydrochloric acid (12 mol/L) precipitated the yellow solid, which was filtered with a glass filter funnel, washed with deionized water and dried in a vacuum oven overnight.The gray solid was obtained and used directly without further purification.

General procedure of radical polymerization:
In an argon atmosphere, 0.01 equivalent (eq) of 2,2'-azobis(2-methylpropionitrile) (AIBN) and 1.0 eq of vinyl derivative were dissolved in 25 mL freshly distilled THF under ice water.After the solid was completely dissolved, the mixture was gradually heated to 55℃ and stirred for 16 h.After the reaction, the mixture was added dropwise to 200 mL methanol to precipitate polymeric materials, then the crude product was filtered, followed by washing with PE and DCM, acetone in sequence.Then the solid was dissolved in deionized water and dialyzed by a dialysis tube (molecular weight cut-off = 1000) for 72 h.
Preparation of full-color polymer films: 0.5 g of polymer powder and a certain amount of organic fluorescent dyes were dissolved in deionized water (10 mL) followed by the vigorous sonication for 10 min under ambient conditions; then the solution was poured into a flask and stirred at 60°C for 1 h to obtain a completely transparent polymer solution; finally the mixed solution was placed in a petri dish and dried in an oven at 70°C overnight to fabricate transparent polymer films for subsequent photophysical and morphological characterizations.

Table 6 .
SACET efficiency of PAMCOOCz2 films without or with doping of different fluorescence emitters at different weight concentrations.