Ion Conduction in Imidazolium Acrylate Ionic Liquids and their Polymers

• Published in: Chemistry of materials 2010-11, Vol.22 (21), p.5814-5822
• Main Authors: Lee, Minjae, Choi, U Hyeok, Colby, Ralph H, Gibson, Harry W
• Format: Article
• Language: English
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm101407d

Polymerizable imidazolium acrylates and their polymers with pendant imidazolium cations were synthesized with hexafluorophosphate and bis(trifluoromethanesulfonyl)imide counterions and characterized using calorimetry and dielectric spectroscopy. The ionic polymers containing a diethyleneoxy unit as an N-substituent on the imidazolium cation display higher ionic conductivities than the analogous N-n-butyl polymers. Using a physical model of electrode polarization, we separate the conductivity of single-ion conductors into number density of conducting ions p and their mobility μ. The monomers invariably possess higher conducting ion number density than the polymers, owing to the cation being part of the polymer, but p is insensitive to the N-substituent. In contrast, the diethyleneoxy N-substituent imparts higher mobility than the n-butyl N-substituent, for both monomers and polymers, owing to a lower binding energy between the imidazolium and the counteranions, which is not directly reflected in glass transition temperatures.