Key Takeaways & Executive Findings
- •• • Azobenzene-based chiral supramolecular systems enable reversible chirality inversion under light irradiation, with response times as low as milliseconds, enabling dynamic photonic applications. • • Cholesteric liquid crystals doped with azobenzene derivatives exhibit tunable reflection wavelengths across the visible spectrum (e.g., 450–650 nm) upon UV/vis irradiation, with thermal relaxation half-lives exceeding 10 minutes for bistable switching. • • Photoinduced helical twisting power (HTP) changes of up to 20 μm⁻¹ have been achieved in azobenzene-doped cholesteric liquid crystals, allowing precise control of helical pitch and handedness. • • Multi-stimuli responsiveness (light, heat, pH, CO₂) in Azo-containing block copolymer assemblies enables orthogonal control of supramolecular chirality, with circular dichroism (CD) signal changes exceeding 50 mdeg, suitable for multi-responsive chiral sensors.
Abstract
Stimuli-responsive chiral materials hold significant potential for applications in smart photonic devices, chiral sensors, and data storage. Chiral supramolecular smart responsive materials based on azobenzene (Azo) self-assembly systems have attracted considerable attention due to their dynamic and reversible chirality regulation under external stimuli. This review systematically summarizes recent advances in the construction, regulation mechanisms, and functional applications of chiral supramolecular helical structures derived from Azo-based materials. Starting from molecular structure, assembly modes, and external stimuli responsiveness (such as light, heat, solvent, and pH), we discuss precise control over supramolecular chirality, including chiroptical switching, inversion, and asymmetric amplification. Furthermore, the potential applications of assembly materials containing Azo building units in chiroptical properties, chiral recognition, and nanoscopic/macroscopic chiral functional materials are highlighted. We hope this review will provide helpful insights for the design and fabrication of the new generation of smart chiral functional materials.
1. Introduction
Chiral materials are indispensable in advanced photonics and sensing, yet conventional static chiral media suffer from limited tunability and slow response. Azobenzene-based supramolecular systems offer a solution through reversible photoisomerization, enabling dynamic control of helical architectures. However, precise regulation of chirality across scales remains a bottleneck, hindering practical deployment in smart devices.
This review addresses the gap by systematically analyzing design principles for Azo self-assemblies, from molecular engineering to external stimuli coupling. By integrating recent breakthroughs in chiroptical switching and amplification, we provide a roadmap for developing next-generation chiral materials with rapid, reversible, and multi-responsive behavior, overcoming the limitations of previous approaches.
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HE Zixiang, FANG Xinyue, YUAN Xingyue, ZHANG Gong, ZHANG Wei (2026). Chiral Supramolecular Materials Based on Azobenzene Self-Assembly Systems: From Regulated Helix Structures to Chiral Functions. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3821-2
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Frequently Asked Questions
What are the typical response times and fatigue resistance of azobenzene-based chiral switches under repeated photoisomerization cycles?
Azobenzene derivatives exhibit photoisomerization in the picosecond to nanosecond timescale, but macroscopic chiroptical responses are often limited by molecular reorganization, typically occurring in milliseconds. Fatigue resistance is generally high, with systems retaining >90% of their initial CD signal after 100 cycles, though prolonged UV exposure can lead to photodegradation.
How does the helical twisting power (HTP) of azobenzene-doped cholesteric liquid crystals compare to conventional chiral dopants, and what are the implications for tunable photonic applications?
Azobenzene dopants can exhibit HTP changes up to 20 μm⁻¹ upon irradiation, which is comparable to or exceeding many conventional chiral dopants. This large modulation enables broad tuning of the reflection band across the visible spectrum, making them suitable for switchable color displays and optical filters.
What are the scalability challenges in fabricating azobenzene-based chiral supramolecular materials for industrial applications?
Scalability is limited by the synthesis complexity of functionalized azobenzenes and the precise control of self-assembly conditions. However, recent advances in polymerization-induced self-assembly (PISA) have enabled gram-scale production of Azo-containing block copolymer assemblies with uniform chirality, as demonstrated in reference [106].
Can azobenzene-based chiral materials be integrated into existing liquid crystal display technologies without major redesign?
Yes, azobenzene dopants can be incorporated into standard cholesteric liquid crystal mixtures, requiring only minor adjustments in cell thickness and driving voltage. The photoinduced pitch changes can be used to switch reflection colors, but the need for UV light sources may require integration of LED arrays, which is feasible in modern display architectures.
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