pH-Induced Hysteretic Gating of Track-Etched Polycarbonate Membranes: Swelling/Deswelling Behavior of Polyelectrolyte Multilayers in Confined Geometry

详细信息    查看全文

• 作者：Daeyeon Lee ; Adam J. Nolte ; Allison L. Kunz ; Michael F. Rubner ; and Robert E. Cohen
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：July 5, 2006
• 年：2006
• 卷：128
• 期：26
• 页码：8521 - 8529
• 全文大小：580K
• 年卷期：v.128,no.26(July 5, 2006)
• ISSN：1520-5126

文摘

pH-induced hysteretic gating of track-etched polycarbonate membranes (TEPC) has beenachieved by depositing layer-by-layer assembled polyelectrolyte multilayers comprising poly(allylaminehydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS) at a high pH condition (pH > 9.0). Scanningelectron microscopy and transmission electron microscopy showed that the average bilayer thickness ofmultilayers was greater within the cylindrical pores of track-etched polycarbonate membranes comparedto the multilayers on planar substrates (e.g., Si wafers and the face of TEPC membranes). Swelling/deswelling properties of multilayers and gating properties of the multilayer-modified TEPC membraneswere studied by measuring the flux of pH-adjusted deionized water. Large discontinuous changes in thetransmembrane flux were observed, indicating that the multilayers within the cylindrical pores of TEPCmembranes exhibit the discontinuous swelling/deswelling behavior observed previously for planar systems.The degree of swelling as estimated by simple models, however, showed that (PAH/PSS) multilayers inthe confined geometry swelled to smaller extents compared to the same multilayers on planar substratesunder the same conditions. Multilayer-modified membranes showed reversible gating properties as the pHcondition of feed solution was alternated between pH 2.5 and 10.5. In situ atomic force microscopy (AFM)was used to visualize the closing of the pores as a function of time. The hysteretic gating property of themultilayer-modified TEPC membrane was utilized to achieve either a "closed" or "open" state at one pHcondition depending on the pretreatment history, thereby enabling either the retention or passage of high-molecular weight polymers by varying the membrane pretreatment condition.