Thermodynamics of Ion-Containing Polymer Blends and Block Copolymers

Issei Nakamura, Nitash P. Balsara, and Zhen-Gang Wang

Phys. Rev. Lett. 107, 198301 – Published 1 November 2011

Abstract

We develop a theory for the thermodynamics of ion-containing polymer blends and diblock copolymers, taking polyethylene oxide (PEO), polystyrene and lithium salts as an example. We account for the tight binding of ${Li}^{+}$ ions to the PEO, the preferential solvation energy of anions in the PEO domain, the translational entropy of anions, and the ion-pair equilibrium between EO-complexed ${Li}^{+}$ and anion. Our theory is able to predict many features observed in experiments, particularly the systematic dependence in the effective $χ$ parameter on the size of the anions. Furthermore, comparison with the observed linear dependence in the effective $χ$ on salt concentration yields an upper limit for the binding constant of the ion pair.

Received 19 May 2011

DOI:https://doi.org/10.1103/PhysRevLett.107.198301

Authors & Affiliations

Issei Nakamura¹, Nitash P. Balsara², and Zhen-Gang Wang^1,*

¹Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
²Department of Chemical Engineering, University of California, Berkeley, California 94720, USA