When quantum dots meet blue phase liquid crystal elastomers: visualized full-color and mechanically-switchable circularly polarized luminescence

Inspired by the color‐changing abilities of natural organisms, this research focuses on the design and fabrication of mechanochromic liquid crystal photonic crystal thin films with periodic self‐assembly structures. Benefiting from its unique 3D self‐assembled structure with a body‐centered cubic lattice, BP I film exhibits excellent mechanical properties, characterized by superior elasticity and toughness due to the presence of rigid and flexible microdomains and suitable dislocation line volumes. As the strain increases, the structural color of the BP I film demonstrates a repeatable and rapid shift from red to blue, covering the entire visible light spectrum with high reflectivity. The incorporation of fluorescent molecules further enhances the mechanical properties and endowing the film with circularly polarized luminescence under UV light irradiation. Utilizing different fluorescent dyes as inks, arbitrary patterned writing can be performed on the BPI film, enabling specific information hiding and encryption. The prepared label exhibits excellent environmental stability, presenting promising applications in information storage, anti‐counterfeiting, and flexible 3D displays. The study may contribute to a deeper understanding of the relationship between microstructure, mechanical deformation, and optical properties, potentially advancing the development of innovative responsive materials and multifunctional devices.

Mechanochromic 3D Soft Photonic Crystals Enabled Anticounterfeiting and Encryption Information Storage

Wang,

Li,

Yang

et al. 2024

Ultra‐Stable Perovskite Quantum Dot Polymer Films

Tang,

Zhang,

Liao

et al. 2024

Cesium lead halide perovskite quantum dots (QDs) exhibit promising potential due to their excellent optoelectronic properties, but the poor stability and limited processability of it are main obstacles for their practical applications. Here, a facile strategy is reported for the synthesis of ultra‐stable perovskite quantum dot polymer films to overcome these bottlenecks, where the QDs are covalently bonded to polymer chain through thiol‐ene click reaction during photopolymerization process. The QD@polymer film exhibits hydrophobicity and excellent underwater photoluminescent (PL) stability over 240 days without PL decay. Notably, the film can maintain 85% of PL intensity even in a strong acid solution (pH 1) over 135 days, a longest endurance time reported so far in harsh conditions. In addition, the film also presents excellent thermal stability, showing reversible on/off switching behavior over 30 heating‐cooling cycles. Integrating the efficient photoluminescence, ultra‐stability, solution‐processability, and photo‐polymerizability, the QD@polymer system demonstrates a highly desired suitability for various applications, including patterned QD arrays and luminescent textiles. Furthermore, a white light emitting device equipped with the prepared QD@polymer as light‐converting layers achieves white emission with color coordinate of (0.34, 0.33) and a 129% color gamut with 99% coverage of the National Television Standard Committee (NTSC) color space.

Enhanced Circularly Polarized Luminescence Modulation Using Dichroic Conjugated Polymer in Cholesteric Liquid Crystals

Chen,

Li,

Yao

et al. 2024

Negative dichroic dyes are crucial for enhancing the brightness of liquid crystal displays (LCDs) and modulating circularly polarized luminescence (CPL) in cholesteric liquid crystals (CLCs) through supramolecular co‐assembly. However, the majority of fluorescent molecules exhibit positive dichroism, and there is a limited understanding of designing negative dichroic molecules. In this paper, a novel design principle is proposed to construct the negative dichroic polymer by introducing through space charge transfer (TSCT) side chain structure to the polymer backbone. Specifically, two conjugated polymers (P1, P2) are synthesized using the Suzuki coupling reaction of two donor‐acceptor (D‐A) type monomers (V‐type M1 and I‐type M2) with fluorenyl monomer. P1 exhibits negative dichroism, and its orientational order parameter (SF) is up to SFP1 = –0.18. On the contrary, P2 is positive dichroism (SFP2 = + 0.27). This variation arises from the differing orientations of the rigidly functional side chains (SFM1 = + 0.07; SFM2 = + 0.31), which affect the alignment (parallel or perpendicular) of the polymer backbone toward CLCs molecules. This phenomenon facilitates controllable dichroism and precisely modulates the handedness of CPL signals, thereby facilitating the successful implementation of multidimensional information encryption systems in CLCs.