Dual Electric/Magnetic Field-Modulated Nematic Liquid Crystal Smart Window Based on the Supramolecular Doping Effect of Halloysite Nanotube Directors

Nowadays in the environmentally friendly society, smart windows have been viewed as one of the attractive energy-saving technologies for green buildings. However, some inherent defects on anisotropy and compatibility still greatly limit their practical applications. Thus, we first utilized hollow heterocharged halloysite (HAL) nanotubes as the doping agent to build up a 4-cyano-4′-pentylbiphenyl (5CB)-based supramolecular liquid crystal (LC) composite with excellent electro-optical properties. In particular, the chemical modification of 5CB blocks on the surface of HAL nanotubes (5CB-HAL) greatly improved HAL’s compatibility with the host 5CB. In the applied alternating current (AC) electric field with a low frequency (60 Hz), the vertically aligned 5CB-HAL-doped LC composites with a low doping concentration of 1.0 wt % exhibited outstanding electrochromic performances, including high contrast (82%), a rapid response of about 200 ms, low driving threshold (0.157 V/μm), a wide viewing angle (120°), and a smooth running of at least 10,000 cycles. In particular, in situ grown superparamagnetic iron (II, III) oxide nanoparticles above the HAL nanotube surface further endowed this LC system with fresh magnetic modulation and better light tuning. It is anticipated to provide a cheap, facile, reliable, and promising technology for high-performance bimodal smart windows.