Tuning the Performance of Composite Membranes by Optimizing PDMS Content and Cross-Linking Time for Solvent Resistant Nanofiltration

Herein, a series of composite membranes with optimized solvent permeance and rejection are prepared by combining the advantages of hybridization and cross-linking techniques. Polyethylenimine (PEI) and hydroxyl terminated trifluoride polydimethylsiloxane (PDMS) are cross-linked with trimesoyl chloride as the skin layer, which is isotropic rather than hierarchical. The chain mobility of PEI is inhibited upon hybridization and cross-linking, affording enhanced solvent resistance and thermal/mechanical stabilities. The composite membrane achieves high rejection ability with the rejection of PEG 1000 of about 100%. Additionally, the synergy of hydrophilic PEI and hydrophobic PDMS segments gives acceptable solvent permeances for acetone (up to 2.7 L m^-2 h^-1 bar^-1) and ethyl acetate (up to 1.4 L m^-2 h^-1 bar^-1). The membrane microstructures are facilely tuned by regulating PDMS content and cross-linking time, allowing the efficient optimization of solvent resistant nanofiltration performances. Moreover, the operational stability and the separation of lotus seedpod proanthocyanidins-ethanol/water mixtures are investigated to evaluate the practical application of the composite membrane.