Dynamically color-changing polymer-dispersed liquid crystals containing ionic liquid for smart window applications

In this work, we report a bifunctional dynamically colour-changing polymer-dispersed liquid crystals (PDLCs) for smart windows by doping a supporting electrolyte ionic liquid into the conventional PDLC system. The transmittance spectra were used to measure the electrically colour-changing properties of the system, while the electro-optical curves were employed to examine the electrically switchable performances. The SEM was used to observe the surface morphology of the polymer microstructure. The result obtained from this work suggested that such device could obtain four independent states under different electric fields. The initial state was opaque and colourless due to the randomly dispersed liquid crystal droplets. The transparent and colourless state was obtained as a result of reorientation of liquid crystal under alternative current (AC) electric field. The opaque and green state was achieved under direct current (DC) electric field owing to the oxidation reaction in the system. Besides, the transparent and green state was realised via applying DC and AC electric field simultaneously or in steps. The convenience and simplification of switching between the four states enable the system to provide some interesting applications for smart windows.