Proton-conducting polymers with reduced methanol permeation

The permeability of Nafion(R)117 and some types of acid-base and covalently crosslinked blend membranes to methanol was investigated. The methanol cro ssover was measured as a function of time using a gas chromatograph with a flame ionization detector. In comparison to Nafion, the investigated acid-b ase and covalently crosslinked blend membranes show a significant lower per meation rate to methanol. Additionally, another method to reduce the methan ol permeability is presented. In this concept a thin barrier layer is plasm a polymerized on Nafion 117 membranes. It is shown that a plasma polymer la yer with a thickness of 0.3 mu m reduces the permeability to methanol by an order of magnitude. (C) 1999 John Wiley & Sons, Inc.