State of Water in Nafion 117 Proton Exchange Membranes Studied by Dielectric Relaxation Spectroscopy

Abstract

Dynamics of water in Nafion 117 membranes, in the acid form, at two hydration levels and several temperatures were investigated by means of dielectric relaxation spectroscopy in both, low (10−2 to 107 Hz, 25 to −80 °C) and microwave (0.045-26 GHz, 35 °C) frequency regions by employing different experimental setups. Three states of water were identified: a) strongly bound to the sulfonic groups (in agreement with other investigations) forming the first hydration layer; b) loosely bound, surrounding the first layer and c) free water, having similar dynamics as in the bulk state.

Properties of Water in Prestretched Recast Nafion

“…The extent of water adsorption and the physical states of water in ionomeric membranes have been examined, using a variety of techniques, including macroscopic gravimetric and volumetric water uptake, NMR, infrared spectroscopy, radio tracer analyses, and dielectric relaxation spectroscopy. – The results of these studies are particularly important with regard to proton-exchange membranes that are used in hydrogen/oxygen and direct methanol fuel cells. The uptake and mobility of water within these ion-exchange membranes are intimately related to proton conduction, electro-osmotic drag, methanol permeability, and the film’s mechanical properties .…”

“…The uptake and mobility of water within these ion-exchange membranes are intimately related to proton conduction, electro-osmotic drag, methanol permeability, and the film’s mechanical properties . There are numerous studies in the literature regarding water uptake and transport in Nafion perfluorosulfonic acid membranes – and in fuel cell membranes composed of sulfonated poly(arylene ether sulfone), sulfonated poly(ether ether ketone), and sulfonated polyimide …”

“…The uptake and mobility of water within these ion-exchange membranes are intimately related to proton conduction, electro-osmotic drag, methanol permeability, and the film's mechanical properties. 9 There are numerous studies in the literature regarding water uptake and transport in Nafion perfluorosulfonic acid membranes [1][2][3][4][5][6][7][8] and in fuel cell membranes composed of sulfonated poly(arylene ether sulfone), 10 sulfonated poly(ether ether ketone), 11 and sulfonated polyimide. 12 For the specific case of DuPont's Nafion, there is nanophase segregation of the nonpolar fluorinated (Teflon-like) backbone and the hydrophilic side chains (which terminate in sulfonic acid cation-exchange groups) prior to and during exposure to water.…”

The state of understanding of ionic polymer metal composite architecture: a review

“…Each layer contributes to the overall mechanoelectric and electromechanical effects in the IPMC. Research has been conducted to understand the electrode layer comprising of porous electrodes [50][51][52][53][54]30], the intermediate layer [42,55,56] and the polymer layer [57][58][59][60][61]. This research is discussed in the following sections with the aim of better explaining the role that they play in IPMC transduction.…”