Poly(ethylene oxide)/viologen hybrid was prepared, and its electrochemical redox response was analysed in the bulk or in poly(ethylene oxide) (PEG) with a molecular weight of 200 (PEO(200)) We analysed the effect of molecular weight (M(w)) of the PEO part in the hybrid on the mechanical property and redox response in the bulk. Totally amorphous viologen hybrid showed a redox response in the bulk over a wide temperature range. Since the viologen hybrid with a M(w) of the PEO part higher than 2000 showed a freezing point (T-f) the electrochemical response was not observed in the bulk below T-f because of low diffusion coefficient. By adding LiClO4 to the polymerized hybrid, the solidifying transition enthalpy decreased and vanished, reflecting the totally amorphous matrix.