Circularly polarized luminescence (CPL) materials hold significant promise across various fields, including optical displays, disease detection, and asymmetric photochemical synthesis. However, their limited luminescence dissymmetry factor (*g_lum*) has hindered real-world applications. The *g_lum* value, defined as 2 × (*I_L* − *I_R*)/(*I_L* + *I_R*), quantifies CPL performance, ranging from -2 to +2. While various strategies exist for amplifying *g_lum*, such as supramolecular self-assembly, aggregation-induced emission, and incorporation into chiral liquid crystals, achieving high *g_lum* values in the ultraviolet (UV) region remains a challenge. This study aims to address this gap by developing a system capable of generating intense circularly polarized ultraviolet luminescence (CPUVL) with significantly enhanced *g_lum* values, suitable for practical applications, particularly in enantioselective photopolymerization. The approach utilizes triplet-triplet annihilation upconversion (TTA-UC) to generate UV light from visible light excitation, and leverages the amplification effect of chiral nematic liquid crystals to boost the *g_lum* value of the upconverted CPL. The successful generation of such UV light is then applied to trigger and control the stereochemistry of a polymerization reaction. The importance of this research lies in its potential to unlock the full potential of CPL materials for advanced applications.

Existing literature highlights the growing interest in CPL materials and their potential applications. However, the small *g_lum* values reported in organic systems, especially chiral small molecules, limit their practical use. Numerous approaches have been explored to amplify *g_lum*, including supramolecular self-assembly, aggregation-induced emission, energy transfer-involved circularly polarized excitation, and incorporation into chiral liquid crystals. Most successful examples, however, operate in the visible light region. Visible-to-UV upconversion using TTA-UC offers a pathway to overcome this limitation, but existing methods often result in very small *g_lum* values (10⁻⁴ to 10⁻³). Chiral nematic liquid crystals (N*LCs) are known for their ability to amplify CPL, but their application with UV upconverted light has been largely unexplored. This research builds upon previous work demonstrating amplification of CPL through TTA-UC, aiming to significantly increase the *g_lum* for practical applications by using a chiral nematic liquid crystal.

The study employed a combination of chiral and achiral molecules for TTA-UC. The chiral annihilator, R/S-4,12-biphenyl[2,2]paracyclophane (R-/S-TP), was synthesized via Suzuki coupling reactions. The achiral sensitizer was the thermally activated delayed fluorescence (TADF) molecule 4CzIPN. The photophysical properties of R-TP, including absorption and emission spectra, were characterized using UV-Vis and fluorescence spectroscopy. Chiroptical properties were evaluated by Circular Dichroism (CD) and CPL spectroscopy. The TTA-UC process was investigated in toluene solution by varying the concentration of R-/S-TP and 4CzIPN, measuring upconversion emission spectra at different excitation intensities. The efficiency of the upconversion process was determined. Time-resolved upconverted emission measurements were conducted to confirm the TTA-UC mechanism. The mixture of the chiral annihilator and the TADF sensitizer was then incorporated into a room-temperature nematic liquid crystal (5CB) to create an induced N*LC. The resulting UC-CPUVL properties were characterized, focusing on the amplification of the *g_lum* value. Finally, the UC-CPUVL generated from the N*LC system was used to trigger the enantioselective photopolymerization of diacetylene, 2,4-nonadecanediynoic acid (NA), and the resulting product was analyzed by CD spectroscopy to assess the stereoselectivity. Various spectroscopic techniques, including ¹H NMR, MALDI-FTMS, UV-Vis, fluorescence, CD, CPL, and time-correlated single photon counting were employed for characterization throughout the study.

The research demonstrated the successful generation of visible-to-UV UC-CPUVL with a high upconversion quantum efficiency (Φ_UC = 7.9%) using the R/S-TP/4CzIPN pair in toluene. The *g_lum* value of UC-CPUVL was significantly enhanced (9.2 × 10⁻³) compared to the prompt CPUVL (3.1 × 10⁻³) in the solution, demonstrating the amplification effect of TTA-UC on circular polarization. Incorporation of the R/S-TP/4CzIPN pair into 5CB resulted in the formation of an induced N*LC, further enhancing the UC-CPUVL emission and leading to a substantial increase in the *g_lum* value (up to 0.19). This value is about three times larger than the prompt CPL in the N*LC. The enhanced UC-CPUVL, with its amplified *g_lum* value, was successfully employed to initiate the enantioselective photopolymerization of diacetylene (NA). The resulting polydiacetylene (PDA) exhibited a clear Cotton effect in CD spectra, mirroring the handedness of the UC-CPUVL used for initiation, indicating good stereoselectivity. Repeated experiments confirmed the reproducibility of this enantioselective polymerization, demonstrating the reliability and potential of this approach.

The results demonstrate a successful strategy for generating intense UC-CPUVL with a significantly enhanced *g_lum* value. The combination of TTA-UC and chiral N*LC amplification provided a powerful method to overcome the limitations of conventional CPL materials. The high *g_lum* value obtained enabled successful application in enantioselective photopolymerization, achieving good stereoselectivity and reproducibility. This achievement addresses a significant challenge in the field of CPL materials and paves the way for novel applications. The high upconversion quantum efficiency of the system further enhances its practical value. The use of readily available materials makes this approach scalable and practical.

This research successfully achieved sequentially amplified UC-CPUVL, first through TTA-UC and then by integrating the system into chiral liquid crystals. The high *g_lum* value (0.19) enabled the enantioselective photopolymerization of diacetylene with excellent stereoselectivity. This work showcases a novel strategy for utilizing UC-CPUVL in practical applications, offering significant advancements in the field of CPL-active materials. Future research could explore other chiral annihilators and sensitizers to further enhance efficiency and expand the range of possible applications. Investigating different liquid crystal hosts could also lead to further improvements in the system.

While the study successfully demonstrated the concept and application of sequentially amplified UC-CPUVL, certain limitations should be noted. The upconversion quantum yield in the N*LC was relatively lower (2.3%) than in the toluene solution (7.9%), possibly due to challenges in achieving optimal dispersion of the sensitizer/annihilator pair within the liquid crystal matrix. Further optimization of the system composition and processing methods could improve the upconversion efficiency in the N*LC. Additionally, the study focuses on one specific diacetylene monomer. Exploring the scope of this method with other chiral monomers would broaden its potential applications and demonstrate broader utility.