(217g) Interfacial Thermodynamics and Ion Structure in Polyelectrolyte Blends

Sing, C., Massachusetts Institute of Technologyestern University
Olvera de la Cruz, M., Northwestern University
Zwanikken, J., Northwestern University

Polyelectrolyte interfaces have been a subject of intense research over the past few decades, and there are still challenges in this field due to a great deal of difficulty in capturing the disparate length scales that drive the thermodynamic behavior of even the most straightforward systems; phase behavior of polymers on length scales of the chain dimensions couple with the local structure on the molecular scale in ways that are not captured by most current theories.

We present a new method for understanding the phase behavior and interfacial structure of blends comprising of polyelectrolytes that fully accounts for the local ion structure through the use of integral equation methods (liquid state theory) within the context of a self-consistent field theory for polymer blends (SCFT). This hybrid calculation goes well beyond current methods to characterize polyelectrolyte correlations in SCFT formalisms that typically rely on perturbation expansions, and permits the elucidation of physical effects (i.e. electrolyte-driven interfacial narrowing, hard sphere phase separation suppression) that are otherwise difficult to realize in simulation or theory.  

The multiscale nature of this calculation leads to elucidation of interface thermodynamics at the same time as local structure (articulated through pair correlation functions) due to Coulombic interactions. We elaborate on the aspects of polymer blends that can be calculated using this method (interfacial tension, phase diagrams, interface geometry, etc.) and describe the profound effect of ion correlations in these scenarios.