Recent developments in high-density energy storage devices have heightened the search for materials that are mechanically robust and highly tunable. Polyelectrolyte blends and copolymers, consisting of at least one charged species, are ideal candidate materials for fuel cell and battery membranes, as they combine the mechanical stability of the polymer chain with the ion-selective conductivity of the charged backbone. Specifically, using charged constituents in a copolymer has been shown to be a powerful way to control the self-assembled nanostructures in the copolymer by introducing local ionic correlations between the charged backbone and the counterions. With statistical thermodynamic methods, we investigate the influence of ionic correlations on the phase diagram of polyelectrolyte blends and charged-neutral block copolymers. In particular, we demonstrate that highly asymmetric charge cohesion effects can drive the system toward phase separation. This can induce the formation of nanostructures in block copolymers where the continuous phase is the minority, charge-carrying phase. In charged-neutral blends, we observe a triple point at selected electrostatic strengths, where the phases correspond to liquid-liquid phase separation between ion pairs, ion clusters, and liquid-like ordering of ions. The addition of salt to the polyelectrolyte blend can induce re-entrant behavior as the salt concentration is increased.

Multiple phase coexistence in polymer electrolytes

251st National Meeting (2016)

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