Binary Supramolecular Chirality "1/0" Switched by Hierarchical Photoisomerization of a Flower-Like Compound with a Binaphthol Core and Alkyl-Functionalized Azobenzene Side Chains.

Chiral supramolecular assemblies are abundant in nature, but controlling the chirality of artificial systems still remains a challenge. In this work, we developed a system where supramolecular chirality can be controlled between chiral and achiral states, namely a chiral "1/0" switch using a flower-like azobenzene compound with a binaphthol core. Upon photoisomerization by ultraviolet irradiation, the terminal alkyl tails envelop the chiral "centre" with a reduction in the dihedral angle of the binaphthol moiety from 76.1° to 61.4°, like "closing petals". In the doped liquid crystal E7 matrix, this hierarchical conformational transition prevents the transfer of chirality to the host liquid crystal, resulting in a degradation from cholesteric phase (HTP value: 13.84 µm-1 ) to an achiral nematic phase.

Multiscale Interface Effect on Homogeneous Dielectric Structure of ZrO2/Teflon Nanocomposite for Electrowetting Application.

Electrowetting-on-dielectric is a preferred option in practical applications of the electrowetting phenomenon but limited by dielectric and breakdown performances of the dielectric layer. In the present work, a ceramic/polymer nanocomposite as a novel dielectric layer is developed to intensify the overall electrowetting performances by multiscale interface effect. Hereinto, surface fluoro-modified ZrO2 nanoparticles (mZrO2) are dispersed well in AF 1600 matrix to form a mZrO2@AF 1600 nanocomposite. The small addition of mZrO2 improves the dielectric constant of the nanocomposite, and the experimental value is larger than the theoretical value calculated by Maxwell⁻Garnett model, but fits well with the Rahaman⁻Khastgir model. The molecular dynamics simulations with the explicit model further verify the interfacial effect. Meanwhile, double contact angle modulation and higher breakdown field strength (Eb) are obtained. For the three-layer sandwich structure, both the top and bottom AF 1600 layer decrease the surface roughness for better electrowetting reproducibility and wider wettability modulation. The Forlani⁻Minnaja theory related to the empirical relationship between Eb and thickness of dielectric layer fit well with the monolayer structure, but cannot be applied in multi-layer structures. A new relationship is proposed to guide the design of dielectric multi-layers with high breakdown field strength.