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Charge Transport in Imidazolium-Based Homo- and Triblock Poly(ionic liquid)s

Mapesa, Emmanuel U., Chen, Mingtao, Heres, Maximilian F., Harris, Matthew A., Kinsey, Thomas, Wang, Yangyang, Long, Timothy E., Lokitz, Bradley S., Sangoro, Joshua R.
Macromolecules 2019 v.52 no.2 pp. 620-628
ambient temperature, bromides, composite polymers, dielectric spectroscopy, differential scanning calorimetry, glass transition temperature, ionic liquids, polystyrenes
Ion dynamics in a series of imidazolium-based triblock copolymers (triblock co-PILs) are investigated using broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC) and compared to their homopolymer counterparts (homo-PILs). Two calorimetric glass transition temperatures (Tg) are observed corresponding to the charged poly(ionic liquid) (PIL) blocks and noncharged polystyrene (PS) blocks. Varying the counterion from Br– to NTf₂– decreases the Tg of the charged block by over 50 °C, thereby increasing the room-temperature ionic dc conductivity by over 6 orders of magnitude. Interestingly, for a given anion, varying the volume fraction of the charged block, from ∼0.5 to ∼0.8, has very minimal effect on the dc ionic conductivity, indicating that the choice of counterion is the key factor influencing charge transport in these systems.