Disulfonated Poly(arylene ether sulfone) Random Copolymer Blends Tuned for Rapid Water Permeation via Cation Complexation with Poly(ethylene glycol) Oligomers

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• 作者：Chang Hyun Lee ; Desmond VanHouten ; Ozma Lane ; James E. McGrath ; Jianbo Hou ; Louis A. Madsen ; Justin Spano ; Sungsool Wi ; Joseph Cook ; Wei Xie ; Hee Jeung Oh ; Geoffrey M. Geise ; Benny D. Freeman
• 刊名：Chemistry of Materials
• 出版年：2011
• 出版时间：February 22, 2011
• 年：2011
• 卷：23
• 期：4
• 页码：1039-1049
• 全文大小：1147K
• 年卷期：v.23,no.4(February 22, 2011)
• ISSN：1520-5002

文摘

Here we present fundamental studies of a new blending strategy for enhancing water permeability in ionomeric reverse osmosis membrane materials. A random disulfonated poly(arylene ether sulfone) copolymer containing 20 mol percent hydrophilic units (BPS-20) in the potassium salt (鈭扴O₃K) form was blended with hydroxyl-terminated poly(ethylene glycol) oligomers (PEG, M_n= 600鈭?鈥?00) to increase the water permeability of BPS-20. Blending PEG with the copolymer resulted in pseudoimmobilization of the BPS-20 polymer chains because PEG complexes with cations in the sulfonated polymer matrix. Strong ion鈭抎ipole interactions between the potassium ions of the BPS-20 sulfonate groups (鈭扴O₃K) and the PEG oxyethylene (鈭扖H₂CH₂O鈭? groups were observed via NMR spectroscopy. These interactions are similar to those reported between crown ethers and free alkali metal systems. The PEG oligomers were compatible with the copolymer at 30 掳C in an aqueous environment. Transparent and ductile BPS-20_PEG blend films exhibited a Fox鈭扚lory-like glass transition temperature depression as the PEG volume fraction increased. This depression depended on both PEG chain length and concentration. Both ion鈭抎ipole interactions and high coordination of 鈭扖H₂CH₂O鈭?with 鈭扴O₃K yielded a defined and interconnected hydrophilic channel structure. The water permeability and free volume of BPS-20_PEG blend films containing 5 or 10 wt % PEG increased relative to BPS-20. The blend films, however, exhibited reduced sodium chloride (NaCl) rejection compared to BPS-20. Addition of PEG did not significantly alter the material鈥檚 dry- and hydrated-state mechanical properties. Unlike commercial state-of-the-art polyamide RO membranes, the blend materials do not degrade when exposed to aqueous chlorine (hypochlorite) at pH 4. This comprehensive suite of measurements provides understanding of the molecular and morphological features needed for rational design of next-generation, chlorine-tolerant water purification materials.