Evolution of the Phase Transition in the Nematic Phase of a Liquid Crystal Doped with Metallic Nanoparticles

Polymer-dispersed liquid crystal (PDLC) films containing nanosized droplets of nematic liquid crystal (NLC) with metallic nanoparticle (NP) additives were investigated for potential use in display devices. Polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) methods showed that PDLC films with low concentrations of NPs significantly alter the optical properties (transmission coefficient, threshold voltage, contrast and absorption coefficients) of the materials under study. It was found that, with a constant UV irradiation intensity, the dye concentration can be optimized to ensure uniform droplet size, higher light transmission, and increased contrast coefficient. Using the Beer-Lambert equation, absorption and extinction coefficients were obtained by measuring the light transmission of PDLC films. It was discovered that the liquid crystal droplets in the PDLC films predominantly adopt a bipolar configuration. A higher content of metallic nanoparticles leads to a decrease in the clearing temperature and a reduction in light transmission due to the lowered order parameter caused by thermal fluctuations. Numerical calculation results showed that the maximum contrast coefficient for PDLC films with nanoparticle content is 2.55 times higher than the minimum contrast coefficient of the films in their initial state. Possible mechanisms for the implementation of these results have been proposed for the creation of flexible liquid crystal display elements used in environmentally friendly technologies.