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Proton-exchange-induced configuration rearrangement in a poly(ionic liquid) solution: a NMR study

journal contribution
posted on 02.11.2017, 00:00 authored by Haijin Zhu, Hengrui Yang, Jiaye Li, Kristine Barlow, Lingxue KongLingxue Kong, David Mecerreyes, Douglas R MacFarlane, Maria ForsythMaria Forsyth
Polymeric ionic liquids have emerged recently as a promising alternative to traditional polymers as the polymer electrolyte membrane materials of choice because of their strongly decoupled dynamics between the polymer backbone and the counterions. Knowledge of proton exchange and transport mechanism in such materials is critical to the design and development of new poly(ionic liquid) materials with improved electrochemical properties. Our NMR results show that the proton exchange between the labile proton of the diethylmethylammonium (NH122) cation and H2O molecules is accompanied by a concerted configuration rearrangement of the ammonium. Through a combination of PFG-NMR and proton relaxation (line width) analysis, we demonstrate that at lower temperatures the labile proton diffuses along with the NH122 ammonium cation as an integral unit, whereas at higher temperatures the NH/H2O proton exchange sets in gradually, and the PFG-NMR measured diffusion coefficient is a population-averaged value between the two exchanging sites.

History

Journal

Journal of Physical Chemistry Letters

Volume

8

Issue

21

Pagination

5355 - 5359

Publisher

American Chemical Society

Location

Washington, D.C.

ISSN

1948-7185

eISSN

1948-7185

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2017, American Chemical Society