Positional Isomerism-Mediated Copolymerization Realizing the Continuous Luminescence Color-Tuning of Liquid-Crystalline Polymers

Abstract

Liquid crystals with color-tunable light emission are important for a variety of applications; however, achieving multicolor light-emitting liquid crystals whose emission colors can be fine-tuned remains challenging because the limited derivatization of mesogenic fluorophores disfavors the diversity of the emission. Here, we present a positional isomerism-mediated copolymerization strategy to obtain liquid-crystalline polymers with continuous luminescence color-tuning ability. The introduced α−/β-cyanostilbene positional isomers possess very similar molecular structures, thus reducing the risk of assembly heterogeneity and facilitating the formation of a homogeneous and consistent liquid crystal mesophase. Meanwhile, a significant electronic effect was caused for fluorophores with positional isomerization, allowing the efficient tuning of emission colors via copolymerization. Especially with a gradual change in the composition of the copolymers, the emission color shift behaved in a continuous manner from blue to green. These cyanostilbenebased liquid-crystalline polymers also showed reversible photochromic fluorescence switching ability. This approach highlights the value of positional isomers to prepare color-tunable solid-state light-emitting materials, allowing control and fine-tuning of the emission property while maintaining the ordered assembly ability.

Thermo‐Induced Bathochromic Emission in Columnar Discotic Liquid Crystals Realized by Intramolecular Planarization

“…Thermochromic fluorescent materials exhibit remarkable emission color change in response to temperature, and such materials have been widely explored because of their potential for applications in data storage, temperature sensors, and optoelectronic devices [1–6] . Fluorescent liquid crystal (LC) materials are effective assets in this aspect by combining remarkable solid‐state light emission and thermotropic polymorphic molecular order [7–22] . To induce the formation of stable LC phases, various secondary interactions among the mesogenic fluorophores are usually introduced, which tends to cause intermolecular electronic coupling and as a result leads to excimer emission in the ordered LC solid [23–31] .…”

“…[1][2][3][4][5][6] Fluorescent liquid crystal (LC) materials are effective assets in this aspect by combining remarkable solid-state light emission and thermotropic polymorphic molecular order. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] To induce the formation of stable LC phases, various secondary interactions among the mesogenic fluorophores are usually introduced, which tends to cause intermolecular electronic coupling and as a result leads to excimer emission in the ordered LC solid. [23][24][25][26][27][28][29][30][31] As excimer emission is usually sensitive to temperature, most of the fluorescent LCs exhibit blue-shifted emission upon increasing temperature due to the transition from excimer to monomer emission.…”

Recent advances in photoresponsive fluorescent materials based on [2+2] photocycloaddition reactions

“…Recently, Tian group 94 has successfully synthesised a class of liquid crystal polymers with photochromic fluorescence switching capability using a copolymerisation strategy (Fig. 15).…”

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

“…[26][27][28][29][30] For example, Chen and Tian et al synthesized a set of SCLCPs by tethering cyanostilbene mesogens to polynorbornene or polymethacrylate as pendants. [31][32][33] The resulting SCLCPs possess tunable supramolecular structures and photochromic characteristics. Moreover, complexing linear polymer and small molecules by non-covalent interaction (e. g., hydrogen bonding and electrostatic interactions) is a more effective and facile way to construct functional materials.…”

“…For example, Chen and Tian et al. synthesized a set of SCLCPs by tethering cyanostilbene mesogens to polynorbornene or polymethacrylate as pendants [31–33] . The resulting SCLCPs possess tunable supramolecular structures and photochromic characteristics.…”