Effects of chemically functionalized TiO2 nanoparticles on the UV-shielding characteristics of polymer-dispersed liquid crystals

Recently, smart windows based on polymer-dispersed liquid crystals (PDLCs) composites have garnered enormous interest owing to their electrically switchable properties. However, the low UV-shielding characteristics of these films limit their widespread application. Here, we reported novel PDLC composite films doped with functionalized TiO2 nanoparticles (NPs) to enhance the UV-shielding efficiency. The TiO2 NPs were chemically functionalized by 3-aminopropyltriethoxysilane (APTS) and 3-methacryloxypropyltrimethoxysilane (MPTS), respectively. Scanning electron microscopy (SEM) studies revealed that APTS functionalized TiO2 NPs tended to cluster in the polymer network instead of liquid crystal droplets, and MPTS functionalized TiO2 NPs were independently and uniformly dispersed in the polymer network. Particularly, optical studies showed that the TiO2(MPTS)/PDLC composite film can effectively shield 95.9% UV light at on-state, and 99.16% at off-state. Furthermore, compared to traditional PDLC film (without TiO2 NPs), the total response time of the TiO2(MPTS)/PDLC film is reduced from 60.4 to 13.4 ms, and the contrast ratio (CR) was increased by more than twofold from 35.6 to 97.26.