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

Abstract

Ion\ndynamics in a series of imidazolium-based triblock copolymers\n(triblock co-PILs) are investigated using broadband dielectric spectroscopy\n(BDS) and differential scanning calorimetry (DSC) and compared to\ntheir homopolymer counterparts (homo-PILs). Two calorimetric glass\ntransition temperatures (<i><i>T</i></i>_g) are observed corresponding to the charged poly­(ionic liquid) (PIL)\nblocks and noncharged polystyrene (PS) blocks. Varying the counterion\nfrom Br^– to NTf₂^– decreases the <i><i>T</i></i>_g of the charged block by over 50 °C, thereby\nincreasing the room-temperature ionic dc conductivity by over 6 orders\nof magnitude. Interestingly, for a given anion, varying the volume\nfraction of the charged block, from ∼0.5 to ∼0.8, has\nvery minimal effect on the dc ionic conductivity, indicating that\nthe choice of counterion is the key factor influencing charge transport\nin these systems.