Construction of Loose PVDF Composite Membrane by Solvent Induced Crosslinking of PEI Macromolecules

This study proposes a novel methodology for constructing functional separation membranes on polyvinylidene fluoride (PVDF) substrates through precise modulation of polyethyleneimine (PEI) macromolecular chain conformation in solvent systems with varying polarity parameters. Preparation of PVDF/styrene-maleic anhydride copolymer (SMA) blend membranes via non-solvent induced phase separation (NIPS). Surface functionalization is achieved through covalent crosslinking between PEI and anhydride groups on PVDF/SMA membranes. Systematic investigation reveals that solvent polarity (water, ethanol, glycero, and liquid paraffin) critically influences PEI chain conformations, governing both the separation layer microstructure and decolorization efficiency. The water-induced PEI (S1) membrane exhibits a synergistic separation mechanism combining size sieving and electrostatic interaction, achieving Congo red retention rates exceeding 99% and methyl blue retention over 90%. Compared to PEI (S1) membrane, PEI (S4) membrane treated with liquid paraffin shows a 60% decrease in permeation flux. In addition, the PEI (S1) membrane maintains 98.5% separation efficiency in continuous dye purification tests. This study contributes novel theoretical perspectives to macromolecular conformation engineering and establishes PVDF composite membranes with excellent permeability.