NH4CF3SO3 has been used to dope thermoplastic polyurethane (TPU) with soft segments (SS) of poly(tetramethylene glycol) (PTMG) and poly(propylene glycol) (PPG), each having a SS molecular weight (M(W)) = 1000 g/mol. The PTMG-based TPU was examined at salt concentrations from 0.15 to 2.00 mmol/g of TPU at a constant hard segment (HS) concentration of 20%. The PPG-based TPUs of HS concentrations varying from 20% to 50% were doped at a single salt concentration of 0.67 mmol/g of TPU. Although room temperature ionic conductivities are low (similar to 1 x 10(-8) S/cm), these systems can be used to elucidate the relationship between structure and morphology and between structure and ionic conductivity. In the PPG-based TPU/NH4CF3SO3 system, in which the conductivity follows a VTF form as a function of temperature, the salt is dissociated and ionic conductivity at 100 degrees C is similar to 1 x 10(-5) S/cm. However, in the PTMG-based TPU/NH4CF3SO3 system, in which the conductivity temperature behavior is Arrhenius at low temperatures and VTF at higher temperatures, the salt is not completely dissociated, and conductivity at 100 degrees C is about 1.5 x 10(-7) S/cm. Phenomenological and effective medium theories have been used to fit the experimental conductivity data with good agreement.