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

Polymer-liquid crystals (PLCs) are common materials for smart windows. However, PLC smart windows usually require high driving voltage to maintain transparency. We synthesized a novel PLC smart film by doping multi-wall carbon nanotubes (MWCNTs) into a reverse-mode polymer network liquid crystal (R-PNLC). It is found that doping MWCNTs could effectively reduce the threshold voltage (V_th) of R-PNLC from 19.0 V to 8.4 V. Due to co-orientation between MWCNT and LC molecules, the doped R-PNLC is able to maintain a high transmittance of visible light (∼ 80%) without an applied electric field. We find that doping MWCNTs could change the frequency modulation property of R-PNLC. The doped R-PNLC exhibits a wider frequency modulation range up to 40000 Hz, while the frequency modulation of the undoped R-PNLC reached to a saturation at 23000 Hz. We also tested the electromagnetic interference (EMI) shielding efficiency of R-PNLC and find that the EMI shielding efficiency could be improved by doping only 0.01 wt% MWCNTs into the system. The total shielding effectiveness of 0.01 wt% MWCNT doped R-PNLC was up to 14.91 dB in the frequency band of 5.38–8.17 GHz. This study demonstrates that the films are potentially useful for low-energy-consumption smart windows with enhanced electromagnetic shielding capability.