Impact of magnetic nanoparticles on the stability of blue phase and twist-grain boundary A phases

Abstract

We investigate experimentally the impact of roughly spherular magnetic maghemite (γ-Fe2O3) nanoparticles (NPs) on the stabilization of lattices of topological line defects in liquid crystals (LCs). For this purpose, we exploit chiral CE8 LCs, which in bulk exhibit blue phases (BPs) possessing line defects (disclinations) in orientational order. Furthermore, the magnetic NPs stabilize twist-grain boundary A (TGBA) and chiral line liquid (NL*) phase possessing screw line defects (dislocations) in translational order. Appropriately surface-decorated NPs stabilize these qualitatively different configurations of line defects owing to the defect core replacement and adaptive defect core targeting mechanisms. Magnetic NPs enhance the temperature window of BPI stability and stabilize TGBA and NL* phases which are absent in bulk LC. Their impact is like the one imposed by strongly geometrically anisotropic NPs, which do not exhibit ferroelectric or ferromagnetic properties.