Rheology of colloidal particles in lyotropic hexagonal liquid crystals: the role of particle loading, shape, and phase transition kinetics

The rheology of self-assembled elongated iron oxyhydroxide (FeOOH) and spherical silica (SiO 2 ) particles in hexagonal (H 1 ) liquid crystal (LC) phase of water and non-ionic surfactant C 12 E 9 is investigated by varying particle concentration and cooling rate. The rheology data shows that both SiO 2 /H 1 and FeOOH/ H 1 LC composites exhibit a higher G ′ when compared to the particle-free H 1 phase, with increasing particle loading and cooling rate. FeOOH particles improve G ′ of the H 1 phase more significantly than SiO 2 particles due to the formation of an interconnected network at H 1 domain boundaries at cooling rates of 1 and 2 ∘ C/min. We hypothesize that self-assembly of particles at domain boundaries leads to a decreased mobility of defects causing an increase in elasticity of particle-laden H 1 phase. Dynamic strain sweep and creep experiments show a non-linear stress–strain relationship attributed to the alignment of micellar cylindrical rods under shear.