Surface and bulk interactions of NafionRTM with polyelectrolytes

Time-dependent adsorption of a high-molecular-weight cationic polyacrylamide from sulfuric acid solution onto a perfluorosulfonate ionomer (Nafion ®) membrane was characterized using X-ray photoelectron spectroscopy (XPS), ultraviolet/visible spectroscopy (UV/Vis), and dynamic contact angle measurements in water. Flourine and nitrogen atomic surface concentrations determined from XPS were well correlated to the adsorbed polymer surface coverage from water contact angle analysis via the Cassie relationship and the adsorbed polymer concentration from UV/Vis, respectively. Cationic polyacrylamide surface coverage remained constant at about 60% for all immersion times investigated.; Perfluorosulfonate ionomer membranes (PFSIs) were cast from Nafion ® solutions (5% w/v in propanol/water) of varying equivalent weights (EW = 950, 1100, and 1200) and all annealed at 100°C under vacuum. Sulfonate group surface concentration on the various membranes and its effect on the adsorption of a cationic polyacrylamide were investigated utilizing XPS. Sulfonate surface concentration was found to be well correlated to the sulfonate bulk concentration obtained from the known equivalent weights of the Nafion ® solutions. Adsorbed cationic polyacrylamide surface coverage was found to be independent of the immersion time in the adsorbate solution.; Surface and bulk interactions of both epoxy and acrylic acid based azo polymer containing carboxylic acid pendant groups onto a Nafion® membrane from aqueous solution was examined. Rapid and irreversible red dyeing of the transparent Nafion® membranes was observed from saturated azo polymer solutions at all pH values investigated except pH 13. Whereas the highest solubility in aqueous solution occurred at pH 13 (with a value of 2.2 and 2.01 g/l, respectively) negligible membrane dyeing was observed. XPS revealed negligible azo polymer surface adsorption at all pH values investigated up to an immersion time of 15 hours and indicated that membrane dyeing results primarily from diffusion of the azo polymer into the membrane bulk. (Abstract shortened by UMI.)...