Strong Microphase Separation and Network Structure Yield High Ionic Conductivity
in Polymerized Ionic Liquid Block Copolymers

A series of strongly microphase-separated polymerized ionic liquid (PIL) diblock copolymers, poly(S-b-AEbIm-TFSI), were used to investigate the relationship between morphology and ionic conductivity.  As compared to a methacrylate-based PIL block copolymer with weak microphase separation, strong microphase separation results in roughly 1.5 to 2 orders of magnitude higher ionic conductivity.  Additionally, ionic conductivity is shown to increase over an order of magnitude as PIL content is increased from 12.2 to 23.6 mol%, corresponding to an increase in the morphology factor, f, and a transition in morphology from 1-D conducting cylindrical pathways to 2-D lamellae to 3-D network structures with continuous conducting microdomains. Lastly, ionic conductivity was compared between an acrylate-based PIL block copolymer and a vinyl-based PIL block copolymer.  The acrylate-based PIL block copolymer displays a half order of magnitude greater conductivity then the vinyl-based block copolymer, demonstrating the importance of PIL chemistry on ionic conductivity.


J.-H. Choi, Y. Ye, Y. A. Elabd, K. I. Winey*, Macromolecules, 46, 5290-5300, 2013.
“Network Structure and Strong Microphase Separation for High Ion Conductivity in Polymerized Ionic Liquid Block Copolymers”