Synthesis Of Brush-like Amphiphilic Copolymers And Their Application In Hydrophilic Modification Of PVDF Microporous Membranes

Polyvinylidene fluoride (PVDF) is a widely used material in membranes. Despite its popularity as a membrane material, the hydrophobic nature of PVDF often results in serious membrane fouling, and thus a low permeation flux in aqueous separation system. To solve this problem, in this work, amphiphilic brush-like copolymers PVDF-g-PEGMA and P(MMA-r-PEGMA) were designed and synthesized. The obtained copolymers were used as additives to perform a hydrophilic modification of PVDF membranes.Amphiphilic PVDF-g-PEGMA copolymer was synthesized via atom transfer radical polymerization (ATRP). The structure and properties of the resulting copolymer was characterized by ~1H-NMR, FTIR, DSC and TGA etc. Then, the PVDF-g-PEGMA was used as additive to prepare blending PVDF membranes by immersion precipitation process. The surface compositions of the prepared membranes were determined by ATR-FTIR. The kinetics process of membrane formation was studied via light transmission experiments. The results showed the addition of amphiphilic copolymer delayed the phase separation progress. Morphological changes on membranes were observed by scanning electronic microscopy (SEM). The results of contact angle measurements and BSA filtration experiments revealed that the hydrophilicity and anti-fouling ability of PVDF membranes were remarkably improved after the introduction of amphiphilic additive.Brush-like P(MMA-r-PEGMA) copolymer was synthesized through free radical polymerization. Then the blending PVDF membranes were prepared by the traditional phase inversion technique with P(MMA-r-PEGMA) as additive. The surface composition of membrane was determined by ATR-FTIR and XPS. Significant upper and bottom surface segregation was observed. The kinetics process for precipitation of PVDF blending membrane was studied through the light transmission experiments. The amphiphilic copolymer delayed the phase separation and made the hydrophilic chains have enough time to segregate to the membrane surface. Morphological changes on the membrane were characterized by SEM. Besides, it was found that the segregation of PVDF-g-PEGMA improved the hydrophilicity, permeation flux, fouling resistance and filtration performances of PVDF membrane by the contact angle measurements, BSA and ink filtration experiments.The blending PVDF hollow fiber membranes were prepared by the dry-wet spinning method using P(MMA-r-PEGMA) as additive. The inner and outer surface composition of membrane was examined by ATR-FTIR and XPS. Significant inner and outer surface segregation of amphiphilic additive was observed. The results of contact angle and filtration experiments suggested that the surface segregation of PVDF-g-PEGMA effectively enhanced the hydrophilicity, permeation flux and separation performances of PVDF hollow fiber membranes. The present work offers a new approach to improve the hydrophilicity and anti-fouling ability of PVDF membranes.