Materials Science Seminar

Phase transitions in polyelectrolytes, polyampholytes and charged colloidsProf. A.Z. Panagiotopoulos
Dept. of Chemical Engineering
Princeton UniversityThis seminar starts with a brief historical overview of simulation studies of phase transitions in fluids dominated by coulombic interactions. It then summarizes recent work on modeling phase transitions in asymmetric ionic and charged polymer systems. The unifying characteristic of these fluids is the close interplay between microstructure and macroscopic properties and the existence of strong interactions or multiple relevant length scales. A fine-lattice discretization approach is used for the computations, combined with multihistogram reweighting. The fine-lattice approach allows close approximation of continuum systems with significant computational savings. For the size- and charge-asymmetric ionic systems we find that the critical parameters scale in a way contrary to the predictions of most integral equation theories. Systems with additional short-range interactions show a wealth of behavior including tricriticality, ionic criticality and conventional (non-ionic) criticality. Polyelectrolyte phase diagrams indicate that the existence of two separate length scales results in a finite critical density extrapolated to infinite chain length. Finally, mixtures of charged colloids and salts show non-monotonic dependence of the critical parameters on salt content and an interplay between the critical lines of the pure salt and colloid that can lead to discontinuous critical lines.

Location: Grace Ford Salvatori Hall Of Letters, Arts & Sciences (GFS) - 116

Audiences: Everyone Is Invited

Contact: Petra Pearce