Zwitterion-treated liquid crystal composites for low-energy-consumption smart windows and wearable devices

As an important type of liquid crystal (LC)-based smart windows for indoor illumination/privacy protection switching and energy conservation, the LC devices from polymer dispersed liquid crystals (PDLCs) have gained more attention for developing flexible intelligent optical films. However, higher voltages are generally needed to drive these devices owing to the large content of polymers and the strong anchoring effect on mesogenic molecules, which not only induces the danger of use but also increases the energy consumption of the devices. In this work, a polymerizable zwitterionic compound, which has little problem with ion accumulation compared to typical electrolytes, is explored as a new class of coating. Zwitterion-treated LC devices are also fabricated using different processing methods. Both the addition of zwitterionic layers and the processing techniques have profound effects on the electric-optical performance of the resultant devices. The driving voltage of the devices is optimized from 58 V to 15–18 V (∼2.9 V/μm to ∼0.75–0.9 V/μm) and the contrast ratio is still above 200. The haze of the optimized flexible smart film is about 89.78% and 5.38% in field-off and field-on states respectively. The electrically switchable transmittance of the flexible zwitterion-treated LC devices is also implemented on windows and the human body. Such a method offers a simple strategy for fabricating the LC devices promising for applications in wearable devices as well as in low-energy-consumption smart windows. © 2022 Elsevier Ltd