Structure-Conductivity Relationships of Block Copolymer Membranes Based on Hydrated Protic Polymerized Ionic Liquids: Effect of Domain Spacing

Gabriel E. Sanoja, Bhooshan C. Popere, Bryan S. Beckingham, Christopher M. Evans, Nathaniel A. Lynd, Rachel A. Segalman

Research output: Contribution to journalArticlepeer-review

Abstract

Elucidating the relationship between chemical structure, morphology, and ionic conductivity is essential for designing novel high-performance materials for electrochemical applications. In this work, the effect of lamellar domain spacing (d) on ionic conductivity (σ) is investigated for a model system of hydrated diblock copolymer based on a protic polymerized ionic liquid. We present a strategy that allows for the synthesis of a well-defined series of narrowly dispersed PS-b-PIL with constant volume fraction of ionic liquid moieties (fIL ≈ 0.39) and with two types of mobile charge carriers: trifluoroacetate anions and protons. These materials self-assemble into ordered lamellar morphologies with variable domain spacing (ca. 20-70 nm) as demonstrated by small-angle X-ray scattering. PS-b-PIL membranes exhibit ionic conductivities above 10-4 S/cm at room temperature, which are independent of domain spacing consistent with their nearly identical water content. The conductivity scaling relationship demonstrated in this paper suggests that a mechanically robust membrane can be designed without compromising its ability to transport ions. In addition, PIL-based membranes exhibit low water uptake (λ ≈ 10) in comparison with many proton-conducting systems reported elsewhere. The low water content of the materials described herein makes them promising candidates for electrochemical devices operating in aqueous electrolytes at low current densities where moderate ion conduction and low product crossover are required.

Original languageEnglish (US)
Pages (from-to)2216-2223
Number of pages8
JournalMacromolecules
Volume49
Issue number6
DOIs
StatePublished - Mar 22 2016
Externally publishedYes

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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