Studies on interactions between Nafion and organic vapours by quartz crystal microbalance

A quartz crystal microbalance (QCM) coated with recast Nafion film has been used to investigate the interaction between various organic solvent vapours (carboxylic acid, alcohol, ketone, amine and aldehyde) and Nafion. The frequency shift caused by different vapours absorbed into Nafion appears to be in the order: amine>carboxylic acid>alcohol>aldehyde>ketone. Amine seems to show the strongest interaction with Nafion among the above polar organic vapours due to the strongest binding energy between NH2 and SO3H of Nafion. Non-polar organic solvents such as hexane and chloroform exhibited a relatively weak interaction with Nafion. Partition coefficients and kinetic binding rate constants between Nafion film and organic vapour were measured. Molecular mechanics calculation gave binding energy change and the optimal conformations of complexes between Nafion and organic vapour molecules. These results were in accordance with the different sorption behaviour of different organic vapours on Nafion film.