Cross-linked polyacrylonitrile/polyethyleneimine–polydimethylsiloxane composite membrane for solvent resistant nanofiltration

• Composite membrane with covalently cross-linked PEI-PDMS as skin layer is prepared.
• Hydrophilic–hydrophobic hybrid network is formed in the skin layer.
• The membrane attains good solvent resistance in both polar and nonpolar solvents.
• The membrane achieves acceptable permeate flux for both polar and nonpolar solvents.
• The membrane shows promising long-term stability for SRNF application.

A new approach to the facile preparation of high-performance composite membrane for solvent resistant nanofiltration is presented herein. Within the composite membrane, hydrophilic polyethyleneimine (PEI) and hydrophobic hydroxyl terminated trifluoride polydimethylsiloxane (PDMS) are cross-linked as skin layer, whereas polyacrylonitrile (PAN) ultrafilitration membrane serves as support layer. The microstructure and physicochemical properties of the membrane are extensively investigated. It is found that PEI chains and PDMS chains are covalently cross-linked via trimesoyl chloride through interfacial polymerization, generating hydrophilic–hydrophobic hybrid network. The cross-linking inhibits the chain mobility of PEI, affording the composite membrane enhanced thermal and mechanical stabilities relative to the membrane without PDMS. Combining the advantages of both hydrophilic and hydrophobic materials endows the composite membrane with excellent solvent resistance properties and nanofiltration performances in both polar solvents and nonpolar solvents, such as isopropanol, butanone, ethyl acetate, and n-heptane. Particularly, the composite membrane achieves permeate fluxes of 37.8, 3.5, 5.4, and 4.7 L m−2 h−1 for these four solvents, respectively, along with the area swellings below 3.2%. After being equilibrated in these solvents, the composite membrane exhibits good structural stability with molecular weight cut-off of 600. The operation stability of the composite membrane is also explored.

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