Effect of size and concentration of magnetic nanoparticles on blue phase stabilization and electro-optical properties in blue phase liquid crystalline nanocomposites

Abstract

Blue phase liquid crystal material having a wide blue phase range of 7 °C was prepared in a binary mixture of nematic and chiral nematic liquid crystals with optimization of chiral dopant concentration. Magnetic nanoparticles of size 20 nm, 40 nm in varying concentrations (<0.5 wt %) could successfully stabilize the blue phase temperature range. Interestingly, the BP stability increases approximately 7.8 °C with an increase in nanoparticles concentration up to a critical concentration (0.1 wt %) and then gradually decreases at higher concentrations of nickel nanoparticles. A detailed comparative electro-optical study of pure blue phase liquid crystal and size dependent nickel nanoparticles doped blue phase liquid crystals is accomplished. The transmission of light increases up to 42–45% for nickel nanoparticles doped blue phase liquid crystal samples than pure blue phase liquid crystal with negligible residual birefringence. An increase in isotropic temperature was noticed in 40 nm nickel nanoparticles doped sample. Also an improvement in threshold voltage, induced birefringence, contrast ratio and Kerr constant with doping of nickel nanoparticles was observed. The present study is a synergistic correlation of size and concentration of nickel nanoparticles with blue phase liquid crystals and sufficiently productive for developing nanoparticles doped blue phase liquid crystal optical devices in future. • Size and concentration dependent magnetic nanoparticles stabilised blue phase liquid crystals are prepared and studied. • 7.8 °C wide BP range was observed using Ni NPs in BPLCs. • Variation in phase transition temperatures and BP range was noticed with variation in concentration and size of NPs. • An improvement in switching voltage, contrast ratio, birefringence and Kerr constant was observed by stabilization of BPLCs through Ni NPs.