Organizing thermodynamic data obtained from multicomponent polymer electrolytes: Salt-containing polymer blends and block copolymers

Abstract

The objective of this review is to organize literature data on the thermodynamic properties of salt-containing polystyrene/poly(ethylene oxide) (PS/PEO) blends and polystyrene-b-poly(ethylene oxide) (SEO) diblock copolymers. These systems are of interest due to their potential to serve as electrolytes in all-solid rechargeable lithium batteries. Mean-field theories, developed for pure polymer blends and block copolymers, are used to describe phenomenon seen in salt-containing systems. An effective Flory–Huggins interaction parameter, χeff, that increases linearly with salt concentration is used to describe the effect of salt addition for both blends and block copolymers. Segregation strength, χeffN, where N is the chain length of the homopolymers or block copolymers, is used to map phase behavior of salty systems as a function of composition. Domain spacing of salt-containing block copolymers is normalized to account for the effect of copolymer composition using an expression obtained in the weak segregation limit. The phase behavior of salty blends, salty block copolymers, and domain spacings of the latter systems, are presented as a function of chain length, composition and salt concentration on universal plots. While the proposed framework has limitations, the universal plots should serve as a starting point for organizing data from other salt-containing polymer mixtures. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1177–1187.