Estimation of the ion conductivity of a PEO-based polyelectrolyte system by molecular modeling

Atomistic molecular modeling has been used to construct amorphous 35.0 wt% water-containing polymer electrolyte materials consisting of two polymers: poly(ethylene oxide) (PEO) and poly(ethylene oxide) with sulfonic acid anion end groups (PEO sulfonic acid anion). The cations in the system are the hydronium ion, which simulates the classical diffusion of the hydronium ion and a particle called proton, which simulates the proton hopping mechanism. The possibility of the ions to move together with the polymers in the matrix is also discussed. The coordination between the ions were calculated and compared with the results for similar systems having different amounts of water. The diffusion coefficients for the ions and the conductivity of the system were calculated. The system was found to be conducting, which agrees with the experimental work. In the simulation, both the hopping and the diffusion mechanism were important in the studied system, while in the simulated system, which contains only one PEO sulfonic acid anion in water, the hopping mechanism dominated. The good correlation between the experimental and simulated results shows that the used model is able to estimate whether the material is conducting or nonconducting. The model can also offer interesting information concerning the possible mechanisms of proton conductivity in polymer electrolyte materials. (C) 2001 Elsevier Science Ltd. All rights reserved.