MWCNT Doped Reverse-Mode Polymer Network Liquid Crystals with Frequency Response Property

Polymer-liquid crystals (PLC) is a common material for smart windows. However, PLC smart windows usually require high driving voltage to maintain transparency. In this work, we synthesized a novel PLC smart film by doping multi-wall carbon nanotubes (MWCNT) into a reverse-mode polymer network liquid crystal (R-PNLC). It was found that doping MWCNT could effectively reduce the threshold voltage (Vth) of R-PNLC from 19.0V to 8.4V. Due to co-orientation between MWCNT and LC molecules, the doped R-PNLC was able to maintain a high transmittance of visible light (~80%) without an applied electric field. We found that doping MWCNT could change the frequency modulation property of R-PNLC. The doped R-PNLC exhibits a wider frequency modulation range up to 40,000Hz, while the frequency modulation of the undoped R-PNLC reached to a saturation at 23,000 Hz. We also tested the electromagnetic interference (EMI) shielding efficiency of R-PNLC and found that the EMI shielding efficiency could be improved by doping only 0.01wt% MWCNT into the system. The total shielding effectiveness (SET) value of 0.01wt% MWCNT doped R-PNLC was up to 14.91 dB during frequency band of 5.38 GHz-8.17 GHz. This study demonstrates that the films are potentially useful for low-energy-consumption smart windows with enhanced electromagnetic shielding capability.