Microstructure and viscoelasticity of thermoreversible gels composed of anisotropic particles with short-range interactions*

The rheology and microstructure of colloidal dispersions of anisotropic particles is of significant interest to the field of science and technology. However, the effect of aspect ratio and interactions on the microstructure and viscoelastic behavior of anisotropic particles is still in its infancy. To quantify these effects, we study the temperature-induced state change of a colloidal anisotropic model system of octadecyl-coated silica rods with dimensions 30 – 300 nm, also termed as adhesive hard rods (AHR). On suspending AHR in tetradecane, it exhibits thermoreversible transition from a fluid-like state to gel state upon cooling from 40 to 15°C. While this temperature-driven change visually appears like a liquid - soft solid transition, we investigate the precise microstructure responsible for the soft solid state. The gelation behavior is studied at different aspect ratio and attraction strength of the AHR. We also study the flow behavior of AHR gels under deformation and correlate it with the local microstructural changes. The flow behavior of AHR system can guide in understanding the response of complex anisotropic biological systems.