Nafion^(TM)膜表面改性──用等离子体聚合方法提高膜的阳离子选择性

Surface Modification of Ion Exchange Membrane(Nafion^(TM) )── The Enhancement of Cation Selectivity by Plasma Polymerization Process

采用辉光放电等离子体聚合方法 ,以 C2 H4 和 NH3 为单体 ,在 Nafion TM膜表面沉积一层含氨基及酰氨基的类聚乙烯阴离子交换膜 ,提高了 Nafion TM膜对阳离子的选择性 ,同时不显著增加膜电阻 .由 SEM确定该等离子体聚合膜厚约 0 .5μm,用红外光谱及 X光电子能谱表征膜结构 .采用四电极法测量膜电阻 ,膜对质子的选择性由 Cu2 + 的迁移数 t Cu表征 ,用二室隔膜装置 (0 .2 5mol/L Cu Cl2 -0 .5mol/L HCl|等离子体处理膜 |1 mol/L HCl)测量 t Cu. O2 等离子体预处理 Nafion TM膜有利于沉积膜在 Nafion TM膜上的沉积并与 Nafion TM膜紧密结合 .经改性后的 Nafion TM膜电阻值仍然很小 ,在 1 mol/L HCl溶液中电阻小于 0 .5Ω·

An ultra thin anionic exchange layer containing —NH 2 and —CONH 2 was deposited on the surface of Nafion TM membrane. This layer was deposited from ethylene and ammonia using a glow discharge plasma polymerization technique. The SEM, ATR(attenuated total reflection) spectra and XPS(X ray photoelectron spectroscopy) showed that the resulted plasma polymers containing —NH 2 and —CONH 2 was about 0 5 μm thick. The proton perm selectivity of plasma modified Nafion TM membrane was expressed by t Cu , the transference number of the Cu 2+ ion through the membrane which was determined by using NafionTM membrane as the separator in a typical two compartment cell(0 25 mol/L CuCl 2 0 5mol/L HCl ｜plasma modified Nafion TM membrane｜1 mol/L HCl). Pretreatment of the Nafion TM membrane by oxygen sputtering enhanced the adhesion of plasma polymer onto its surface. The plasma treated membrane exhibited a high perm selectivity and its resistance in 1 mol/L HCl was only a little bit higher than Nafion TM membrane(<0.5 Ω·cm 2).