Molecular Dynamics Study of the Methanol Effect on the Membrane Morphology of Perfluorosulfonic Ionomer

Singo Urata, Jun Irisawa, Akira Takada, Wataru Shinoda, Seiji Tsuzuki, and Masuhiro Mikami

J. Phys. Chem. B 109 17274 (2005).

The membranes of perfluorosulfonic acid polymer swollen in 10 to 80wt% methanol solution were investigated to elucidate methanol effect on their morphologies, such as size of solvent cluster, solvent location and polymer structure by using isothermal-isobaric molecular dynamics simulations. In higher methanol concentration, we found less spherical solvent aggregation and more spread polymer structure because of the ampholytic nature of methanol. The partial radial distribution functions between solvent oxygen and fluorocarbons, which composed of the main-chain, clearly show that methanol locates closer to polymer matrix than water. On the other hand, water preferentially located in the vicinity of acidic head group, SO3-, compared with methanol, although both have the similar attractive interaction energies to the acidic group. Furthermore, we discussed solvents dynamics and hydrogen bonding between sulfonic oxygen and solvents O-H groups.

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