Colloidal Gelation of Thermo-Responsive Microgel Mixture Suspensions*

Concentrated suspensions of microgels composed of thermo-responsive polymer such as poly(N-isopropylacrylamide) (PNIPA) exhibit various states, i.e., repulsive glass, dispersion, (attractive) colloidal gel, depending on temperature (T), particle concentration, surface charge density. The heating reduces the volume of the microgels, and also substantially changes the type of interparticle interaction from repulsive to attractive when T across the LCST, resulting in the formation of colloidal gel. Present work focuses on the dense suspensions of the microgel mixtures of PNIPA and the homologue with different LCSTs. We show that the rheological properties of the mixture suspensions are pronouncedly affected by the mixing ratio. The T-dependent viscoelastic properties of the mixture suspensions are interpreted by considering the T-dependence of the volume fraction and the type of interparticle interaction of each component.[1]
[1] S. Minami, T. Watanabe, D. Suzuki, K. Urayama, Soft Matter, 14, 1596-1607, 2018