Rheology of colloidal particles in lyotropic hexagonal liquid crystals: the role of particle loading, shape, and phase transition kinetics
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The rheology of self-assembled elongated iron oxyhydroxide (FeOOH) and spherical silica (SiO2) particles in hexagonal (H1) liquid crystal (LC) phase of water and non-ionic surfactant C12E9 is investigated by varying particle concentration and cooling rate. The rheology data shows that both SiO2/H1 and FeOOH/ H1 LC composites exhibit a higher G′ when compared to the particle-free H1 phase, with increasing particle loading and cooling rate. FeOOH particles improve G′ of the H1 phase more significantly than SiO2 particles due to the formation of an interconnected network at H1 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 H1 phase. Dynamic strain sweep and creep experiments show a non-linear stress–strain relationship attributed to the alignment of micellar cylindrical rods under shear.
KeywordsHexagonal phase Liquid crystals Rheology Colloidal particles
The authors thank Prof. S. S. Velankar (U. Pitt) and Prof Norman J. Wagner (U Del) for fruitful discussion and comments. Prachi Thareja gratefully acknowledges the Science and Engineering Research Board (SERB), Department of Science and Technology (DST), Government of India, for funding this work.
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Conflict of interests
The authors declare that they have no competing interests.
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