Surface modification of ion exchange membrane (Nafion (TM)) - The enhancement of cation selectivity by plasma polymerization process

An ultra-thin anionic exchange layer containing -NH2 and -CONH2 was deposit ed on the surface of Nafion(TM) membrane. This layer was deposited from eth ylene and ammonia using a glow-discharge plasma polymerization technique. T he SEM, ATR(attenuated total reflection) spectra and XPS(X-ray photoelectro n spectroscopy) showed that the resulted plasma polymers containing -NH2 an d -CONH2 was about 0.5 mum thick. The proton perm-selectivity of plasma-mod ified Nafion(TM) membrane was expressed by t(Cu), the transference number o f the Cu2+ ion through the membrane which was determined by using NafionTM membrane as the separator in a typical two-compartment cell (0.25 mol/L CuC l2- 0.5mol/L HCl / plasma-modified Nafion(TM) membrane / 1 mol/L HCl), Pret reatment of the Nafion(TM) membrane by oxygen sputtering enhanced the adhes ion of plasma polymer onto its surface. The plasma-treated membrane exhibit ed a high perm-selectivity and its resistance in 1 mol/L HCl was only a lit tle bit higher than Nafion(TM) membrane (<0.5 Ohm . cm(2)).