Comparison Between the Conductivities of Protons Measured Experimentally with the Obtained by Molecular Dynamics Simulations in Sulfonated Polyphenyl Sulfones Membranes

Full Molecular Dynamics was used to simulate separately the diffusion of naked protons and H₃O⁺ hydrated protons across sulfonated polyphenyl sulfones, (sPS). The diffusion coefficient of naked protons is nearly one order of magnitude higher than that of the hydrated protons for the membranes with the lower water uptake (10%). The conductivities simulated at 300 K for the hydrated proton across membranes with water uptake 18% and 30 % are roughly similar to those both experimentally measured for the sPS4 membrane with ion exchange capacity = 1.8 eq/Kg in dry conditions and with water uptake = 24.3 %. The comparison between four sPS membranes shwon the strong dependence of conductivity with the water content into the membranes. In our study, the conductivity of sPS1 with a 3.1% water content decrease two order of magnitude respect the sPS4 with 24.3 of water content. Simulated conductivities of both naked protons and hydrated protons follow Arrhenius behavior.This work was supported by the Dirección General de Investigación Científica y Técnica (DGICYT), Grant MAT-2005-05648-C02-02, and from IMPIVA of Generalitat Valenciana through project IMCITA/2006/030 is gratefully acknowledged. The authors are also grateful to the Instituto de Tecnología Eléctrica (ITE) de la Universidad Politécnica de Valencia for the financial support