Systems of branched polyethylenimine (BPEI) complexed with sodium triflate (NaTf) and sodium tetraphenylborate (NaBPh4) are examined using FT-IR spectroscopy, differential scanning calorimetry, and impedance spectroscopy. Cation-polymer, cation-anion, and hydrogen-bonding interactions are investigated by evaluating the frequency shifts of the host BPEI upon complexation with the salts. The inductive effect of sodium is highly dependent on its interaction with the anion, with the effect stronger in BPEI:NaBPh4 complexes than in BPEI:NaTf complexes. DSC data show that the glass transition temperatures for the BPEI:NaBPh4 system are significantly higher than the T-g values for the BPEI:NaTf system at the same salt compositions. The ionic conductivities of the BPEI:NaTf complexes are significantly higher than the conductivities of the BPEI:NaBPh4 complexes at all comparable compositions and temperatures. This result is consistent with the DSC data and the greater sodium ion inductive effect in the BPEI:NaBPh4 complexes. The highest conductivity values occur in the 20:1 BPEI: NaTf complex and are on the order of 10(-6) S cm(-1) at 25 degrees C.