Supramolecular Polymerization of Biphenyl-Cyanostilbenes. Triggering Circularly Polarized Luminescence by Self-Assembly

We report on the synthesis of a series of cyano-luminogens with cyanostilbene fragments, benzamide units, and a nonplanar biphenyl core. Benzamide units drive supramolecular polymerization, forming helical H aggregates via kinetically controlled self-assembly. A sergeants-and-soldiers experiment revealed frustrated asymmetry amplification due to the contamination of linear dichroism. The planarization of the central π-conjugated systems enhances aggregation-induced emission affording circularly polarized luminescence-active helical aggregates.

Fluorescence and Phosphorescence Dual-Emission Liquid Crystal Polymer Optical Waveguide for Logical Gate

Information security has emerged as a critical concern in contemporary society. Leveraging optical logic gates with dual-emission characteristics offers a promising approach to enhancing information security. However, designing active optical waveguide materials (OWMs) capable of fluorescence-phosphorescence dual emission remains a significant challenge. In this study, we present a room-temperature phosphorescent liquid crystalline polymer (RTP LCP) as active OWMs exhibiting fluorescence-phosphorescence dual emission and a low optical loss coefficient (OLC) for implementation in optical logic gates. The resulting RTP LCP exhibits a smectic phase between 25 °C and 90 °C, followed by nematic phase between 90 °C and 110 °C, with a phosphorescence lifetime of 2.77 ms. Subsequently, the RTP LCP is processed into oriented liquid crystal fibers and encapsulated in polymethyl methacrylate. Optical waveguide experiments demonstrate that these oriented liquid crystal fibers exhibit fluorescence-phosphorescence dual emission, with low OLCs of 0.20 dB/mm at 490 nm and 0.17 dB/mm at 565 nm. Furthermore, these dual-emission active OWMs are successfully applied to optical logic gates. This work holds significant implications for the development of active OWMs with fluorescence-phosphorescence dual emission, advancing their potential applications in optical logic gates.

Aggregation-Induced Emission-Active Cyanostilbene-Based Liquid Crystals: Self-Assembly, Photophysical Property, and Multiresponsive Behavior

Cyanostilbene (CS)-related conjugated groups can be considered as dual functional groups of AIEgen and mesogen to construct photoluminescent liquid crystals, and it is essential to study the relationship between their molecular structures and compound properties systematically. In this paper, we designed and synthesized linear and bent-shaped CS derivatives containing ester- and amide-connecting groups and different substituted numbers of alkoxy tails. Their phase behaviors and photophysical properties were investigated in depth. The bent-shaped compounds with the mono-substituted alkoxy tail exhibit a smectic C structure, and those containing two or three alkoxy tails possess a hexagonal columnar phase structure. The compounds exhibit aggregation-induced emission (AIE) properties in tetrahydrofuran (THF)/water mixtures. When the water fraction increases to a certain threshold, a dramatic increase in emission intensity and a red-shift in the fluorescence emission peak are detected. The emission peaks of the ester-type compounds in solid states are around 480 nm, and those of the amide-type compounds are extended to 590 nm, exhibiting versatile luminescent colors. Moreover, thermochromic and photochromic fluorescence-responsive properties are witnessed in these CS derivatives. This work provides a new strategy for the design and synthesis of fluorescent liquid crystalline materials with multiple response properties.

Supramolecular Structure and Photo-Thermo-Electric Property of Hydrogen-Bonded Liquid Crystalline Polymer Containing Poly(4-vinylpridine) and Cyanostilbene Side Chains

A series of side-chain liquid crystalline polymers P4VP(CN-DBE)_x , where x is the molar ratio of cyanostilbene (CN-DBE) to poly(4-vinylpyridine) (P4VP) repeating unit, was synthesized based on the intermolecular hydrogen bonding between P4VP and CN-DBE. Their luminescent property, liquid crystalline structure and photo-thermo-electric property were elucidated using photoluminescence spectra, X-ray diffraction, thermal imaging and thermoelectric experiments. With the increase of x, the supramolecular system can be changed from lamellar structure to hexagonal columnar structure. Moreover, the P4VP(CN-DBE)_x polymer with columnar structure exhibits more efficient photothermal effect. The temperature of P4VP(CN-DBE)_0.6 can rise to 130 °C within 10 s under the irradiation of ultraviolet lamp. In addition, the supramolecular system possesses unique photo-thermo-electric conversion ability, and 25 mA current can be detected in the circuit coupled with the thermoelectric module. This work broadens the potential applications of hydrogen-bonded polymer, and provides a simple and facile strategy to prepare liquid crystalline polymers with photo-thermo-electric property.