Enhanced electro-optical properties of polymer-dispersed liquid crystals co-doped with fluorescent molecules and nanoparticles for multifunctional applications

Functional soft materials that exhibit different application functions under different stimuli are highly desired for the fabrication of advanced devices with excellent performance. Favorable electro-optical properties (low threshold and saturation voltages, high contrast, etc.) are an important basis for polymer-dispersed liquid crystal (PDLC) to achieve applications in electric response anti-counterfeiting, smart windows, privacy windows, and so on. In this work, the co-doping strategy of fluorescent dyes and nanoparticles into PDLC was used to improve its electro-optical properties. Noteworthily, the co-doping effectively suppressed contrast degradation compared to doping with fluorescent dyes only. Multifunctional applications of the co-doped PDLC for UV shielding films, architectural smart windows and privacy windows were investigated. The results of uniaxial tensile test and curvature bending test showed that the prepared flexible film had great stability against external forces and harsh environments. The strategy of hiding the QR code in PDLC device was achieved for the first time by the two-step polymerization method, which realized a sensitive electric response anti-counterfeiting mode. By using fluorescent molecules that show different colors under visible and ultraviolet light, enabling anti-counterfeiting encryption of text and numbers. Thus, our developed fluorescent PDLC provides an approach for novel anti-counterfeiting modes and multifunctional applications of films.