Nano structure of NAFION: a SAXS study

We performed small angle scattering experiments with synchrotron radiation to study the nano structure and the swelling behavior of NAFION polymer mem branes in water-methanol under in situ measurement conditions, which are re levant for their use in direct methanol fuel cells. To retrieve structural information from the scattering data, we propose a model with discrete sand wich like structure elements for the nano structure of the cross-linked cha nnel system within the membrane. They consist of a shell region and an embe dded core region, the latter being either empty or flooded by water-methano l. In summary, the scattering data indicate, that this simple structure mod el is able to describe the swelling behavior of NAFION on a nanometer scale . During swelling we find a shrinking of the core region and a swelling of the shell region, which contains the side-chains of the NAFION molecule. (C ) 2001 Elsevier Science Ltd. All rights reserved.