We report the synthesis and characterization of a series of novel imidazolium cation and bis(trifluoromethane)sulfonimide anion (TFSI-)-based ionic liquid (IL) model compounds and their corresponding polymeric ionic liquids (PILs) with various tethering groups. Ethylene oxide repeating units were attached as tethering groups to an imidazolium cation to optimize the glass transition temperatures (T-g) and ionic conductivities of the PILs. The novel PILs exhibit excellent conductivity values of around 8 x 10(-4) S/cm at room temperature. The thermophysical and electrochemical properties of ILs, including thermal transition, ionic conductivity, and rheological behavior, were characterized to investigate the effect of tethering groups. We conclude that the length of poly(ethylene oxide) tethering group has a tremendous effect on both physical property and electrochemical behavior and that charge carrier density is dominant in defining ionic conductivity with free ILs, whereas ion mobility plays a more important role after polymerization. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1339-1350