Composite Fluorocarbon Membranes by Surface-Initiated Polymerization from Nanoporous Gold-Coated Alumina
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- 作者：Carlos A. Escobar ; Ahmad R. Zulkifli ; Christopher J. Faulkner ; Alex Trzeciak ; G. Kane Jennings
- 刊名：ACS Applied Materials & Interfaces
- 出版年：2012
- 出版时间：February 22, 2012
- 年：2012
- 卷：4
- 期：2
- 页码：906-915
- 全文大小：487K
- 年卷期：v.4,no.2(February 22, 2012)
- ISSN：1944-8252
文摘
This manuscript describes the versatile fabrication and characterization of a novel composite membrane that consists of a porous alumina support, a 100 nm thick nanoporous gold coating, and a selective poly(5-(perfluorohexyl)norbornene) (pNBF6) polymer that can be grown exclusively from the nanoporous gold or throughout the membrane. Integration of the three materials is achieved by means of silane and thiol chemistry, and the use of surface-initiated ring-opening metathesis polymerization (SI鈥揜OMP) to grow the pNBF6. The use of SI鈥揜OMP allows tailoring of the extent of polymerization of pNBF6 throughout the structure by varying polymerization time. Scanning electron microscopy (SEM) images indicate that the thin polymer films cover the structure entirely. Cross-sectional SEM images of the membrane not only corroborate growth of the pNBF6 polymer within both the porous alumina and the nanoporous gold coating but also show the growth of a pNBF6 layer between these porous substrates that lifts the nanoporous gold coating away from the alumina. Advancing contact angle (胃A) measurements show that the surfaces of these composite membranes exhibit both hydrophobic (胃A = 121鈥?29)掳 and oleophobic (胃A = 69鈥?4)掳 behavior due to the fluorocarbon side chains of the pNBF6 polymer that dominate the surface. Results from electrochemical impedance spectroscopy (EIS) confirm that the membranes provide effective barriers to aqueous ions, as evidenced by a resistive impedance on the order of 1 脳 107 惟 cm2. Sulfonation of the polymer backbone substantially enhances ion transport through the composite membrane, as indicated by a 40鈥?0 fold reduction in resistive impedance. Ion transport and selectivity of the membrane change by regulating the polymerization time. The fluorinated nature of the sulfonated polymer renders the membrane selective toward molecules with similar chemical characteristics.