Dual tunability of selective reflection by light and electric field for self-organizing materials

• Published in: Journal of molecular liquids Vol. 400; p. 124540
• Main Authors: Mrukiewicz, Mateusz, Cigl, Martin, Perkowski, Paweł, Karcz, Jakub, Hamplová, Věra, Bubnov, Alexej
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.04.2024
• Subjects: Azobenzene; Cholesteric; Electric field; Liquid crystal; Photoisomerization; Electric field; Cholesteric; Liquid crystal; Photoisomerization; Azobenzene
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2024.124540

[Display omitted] •The selective reflection of light in the oblique helicoidal structure is tunable by the electric field.•Cholesteric mixtures were doped with rod-like, chiral, and bent-shaped azobenzene compounds.•Cholesterics with newly designed photosensitive molecules can be tuned by the electric field and UV light.•The tuning mechanism, reflection coefficient, and response time are related to the structure of azobenzene compounds. The oblique helicoidal structure is formed in right-angle cholesterics under the applied electric field. The electric field changes the pitch and cone angle but preserves the single-harmonic modulation of the refractive index. As a result, in such a supramolecular system, we can tune the selective reflection of light in a broad range. Here, we report that structural colors can be tuned by simultaneously illuminating the structure with UV light and the action of an electric field. The cholesterics with the oblique helicoidal structure were doped with newly designed rod-like, chiral, and bent-shaped azo-photosensitive materials characterized by a very low rate of thermal back cis (Z) – trans (E) isomerization. The E-Z isomerization of the photo-active compounds under UV light causes the red shift of the selective light reflection in the cholesteric mixtures. We found that the molecular structure of the photosensitive materials used affects the reflection coefficient, bandwidth, response time to UV irradiation, and tuning range. The effect was explained by considering the effect of molecular matching, cis–trans isomerization, and electric field action. We investigated the dynamics of molecular changes in the oblique helicoidal structure under the influence of external factors. The designed supramolecular system has the potential application in soft matter UV detectors.