Linear poly(ethylenimine) (LPEI) has been modified by reductive alkylation to form linear poly(N-(2-(2-methoxyethoxy)ethyl)ethylenimine) (LPEI-G2) as verified by nuclear magnetic resonance spectroscopy (NMR). The resulting LPEI-G2 has short methyl-capped oligo(ethylene oxide) side-chains attached to the LPEI backbone. Characterization of pure LPEI-G2 and LPEI-G2 complexed with lithium triflate (LiTf) was carried out over a variety of concentrations using infrared (IR), differential scanning calorimetry (DSC), and impedance techniques. Initial spectroscopic studies indicated that at a 20:1 oxygen atom to lithium ion ratio, “free” ions are the dominant triflate species present. At the same composition, the electrolyte has a Tg of −60°C and a conductivity 7×10−5 S cm−1 at 60°C. The vibrational spectra and conductivity values of samples at O:Li compositions of 20:1 and 5:1 will be discussed.