Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 69: Focus: Polymers in Multi-Component and Aqueous Solutions I - organized by Jens-Uwe Sommer and Debashish Mukherji

CPP 69.6: Topical Talk

Donnerstag, 15. März 2018, 16:45–17:15, C 130

Soft matters in one-phase mixed solvents — •Takeaki Araki — Department of Physics, Kyoto University, Kyoto, Japan

We numerically study charged polymers and colloids in solvent mixtures. Even when the solvent is mixed in the bulk, local concentration inhomogeneities cause the attractive interactions among the solutes. (1) The behaviors of polyelectrolyte chains in solvent mixtures are investigated, taking into account the concentration inhomogeneity and the ionization. When changing the interaction parameters between the solvent components, we found a first-order transition of the polymer conformation. In the mixing state far from the coexistence curve, the polymers behave as semi-flexible chains. In the phase-separated state, on the other hand, they show compact conformations included in the droplets. As the interaction parameters of the mixture are increased, an inhomogeneous concentration field develops around the polymer and induces critical Casimir attractive interactions among the monomers. The competition between the electrostatic interactions and the critical Casimir ones gives rise to drastic changes in the conformation.(2) We studied the behavior of colloidal suspensions in solvent mixtures under shear flows. Far from the phase-separation point, they are well dispersed and the suspension exhibits a Newtonian viscosity. When the mixture is close to the coexistence curve, the particles aggregate by attractive interactions due to the concentration inhomogeneity, and the viscosity of the suspension increases.