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Dynamic Properties of Different Liquid States in Systems with Competing Interactions Studied with Lysozyme Solutions



P. D. Godfrin, P. Falus, L. Porcar, K. Hong, Steven D Hudson, N. J. Wagner, Yun Liu


Recent studies of colloidal systems with a short-range attraction and long-range repulsion (SALR) have been demonstrated to have a generalized phase diagram with multiple liquid states, such as dispersed, random percolated, clustered, and cluster percolated fluids. In this paper, we identify the different liquid states of previous experimentally studied lysozyme samples within this proposed generalized state digram and explore the dynamic properties of each liquid state. We show here that most previoulsy studied lysozyme samples at low and intermediate concentrataions are in the dispersed fluid region while a few high concentration samples are in the random percolated liquid state. In the dispersed fluid region, the short-time diffusion coefficient measured by neutron spin echo agrees well with the long time diffusion coefficient estimated with the solution viscosity. This dynamic feature is maintained even for some samples in the random percolated region. However, the short-time and long-time diffusion coefficents begin to deviate from each other for random percolated fluid states at higher concentration and attraction strength. At high enough concentrations, the mean square displacement can be as slow as those of many glassy colloidal systems at time scales near the characteristic diffusion time even though these lysozyme samples remain in liquid states at the long-time limit. We thus identify the region in the generalized phase diagram where these equilibrium states with extremely slow local dynamics exist to bulk percolation and kinetic arrest (gel and glassy) transitions.
Soft Matter


lysozyme, protein, neutron spin echo, small angle neutron scattering, interaction
Created November 14, 2018, Updated January 31, 2020