Modification Of Poly(Vinylidene Fluoride) Via Atom Transfer Radical Polymerization

In this thesis, modification of poly(vinyliene fluoride) (PVDF) and PVDF microfiltration (MF) membranes using activators generated by electron transfer (AGET ATRP) mediated by iron catalyst and normal ATRP were demonstrated, respectively. The modified PVDF has some special functions, which facilitates wider application of PVDF. The works can be summarized as follows:(1) System I: A novel approach to modify PVDF via iron-mediated AGET ATRP. Iron-mediated atom transfer radical polymerization using activators generated by electron transfer (AGET ATRP) directly from the secondary fluorine atoms on the PVDF backbone, using methyl methacrylate (MMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as the monomers, FeCl3·6H2O as the catalyst, PPh3 as the ligand and vitamin C as the reducing agent, was demonstrated in the presence of limited amounts of air. The successful syntheses of the corresponding graft copolymers PVDF-g-PMMA and PVDF-g-PPEGMA were characterized by 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS), respectively. The graft copolymers PVDF-g-PPEGMA can be readily cast into porous hydrophilic microfiltration (MF) membranes by phase inversion in an aqueous medium. The morphologies were characterized by scanning electron microscopy (SEM). The surface and bulk hydrophilicity were evaluated on the basis of static water contact angle and the steady adsorption of Bovine serumal albumin (BSA). All these results demonstrate that both hydrophilicity and fouling resistance of the PVDF membrane can be improved.(2) System II:Surface modification of PVDF microfiltration (MF) membranes via surface-initiated ATRP. In this method, The PVDF membranes was first grafted with poly(glycidyl methacrylate) (PGMA) by means of surface-initiated ATRP. Then, L-1-phenylethylamine (L-PEA) was reacted with epoxy groups in the grafted PGMA. The surface chemical compositions were characterized by the Fourier transform infrared total reflection spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Thermogravimetric analysis (TGA) was used to estimate the content of the grafted polymers and L-PEA. The morphologies were characterized by scanning electron microscopy (SEM). Filtration experiments were carried out to evaluate the permeability of the modified PVDF membranes. The results show that the modified membrane has higher permeation flux.