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

• Published in: Rheologica acta 2016-01, Vol.55 (1), p.23-36
• Main Authors: Kulkarni, Siddharth, Thareja, Prachi
• Format: Article
• Language: English
• Subjects: Boundaries; Characterization and Evaluation of Materials; Chemistry and Materials Science; Complex Fluids and Microfluidics; Cooling; Cooling rate; Creep (materials); Crystal defects; Domains; Food Science; Liquid crystals; Materials Science; Mechanical Engineering; Original Contribution; Phase transitions; Polymer Sciences; Rheological properties; Rheology; Self-assembly; Silicon dioxide; Soft and Granular Matter; Strain; Stress-strain relationships
• ISSN: 0035-4511; 1435-1528
• DOI: 10.1007/s00397-015-0896-1

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.