Preparation And Properties Of Intelligent Poly(Vinylidene Fluoride) Membranes

On the basis of the analysis of intelligent hydrogel and Poly(vinylidene fluoride) (PVDF) membrane, the environmentally responsive PVDF hollow fiber membrane (HFM) and PVDF plate membrane were prepared using novel approaches: alkaline treatment method and atom transfer radical polymerization (ATRP) using PVDF as a macroinitiator, respectively. The environmentally responsive behavior of PVDF membrane was investigated by the flux of pure water and the rejection of ovalbumin, BSA and polyethylene glycol, respectively. In addition, a new gel thermodynamic model of P(NIPA-co-GMA-Dex) gel was established on the basis of non-ionic gels thermodynamic model, the theory can be used to describe the change of lower critical solution temperature (LCST) of temperature-sensitive gels with the numbers of OH group in the gels.In this paper we demonstrated the first example of the preparation of PVDF-g-PNIPA, PVDF-g-PAAc and PVDF-g-P(NIPA-co-GMA-Dex) composite hydrogel membrane. The structures of membranes were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The effects of alkaline treatment time and concentration of cross-linking agent on grafting yield of PVDF membranes were measured and analyzed. The environmentally responsive behaviors of the three membranes were investigated by the flux of pure water and the rejection of ovalbumin, BSA and polyethylene glycol. The results showed, alkaline treatment method is an effective way for preparing PVDF composite hydrogel membrane; the time of alkaline treatment and concentration of cross-linking agent play an essential role on grafting yield of PVDF. The PVDF composite hydrogel membrane is an intelligent membrane with environment responsibilities and such membrane is useful in controlling the separation of different molecular weight.We also demonstrated the first example of using PVDF as macroinitiator to polymerize temperature sensitive PVDF-g-PNIPA copolymer by ATRP, and DMDP, CuCl and NMP was used as a ligand, cointiator and solvent, respectively. In addition, PVDF-g-PNIPA copolymer was also prepared by alkaline treatment. The PVDF-g-PNIPA membrane was prepared by phase inversion process. The characters of copolymer and the environmentally responsive behavior of PVDF-g-PNIPA membrane were studied. The results showed that PNIPA has been successfully graftedon the PVDF and PVDF-g-PNIPA membrane is an intelligent membrane.In addition, a new gel thermodynamic model of P(NIPA-co-GMA-Dex) gel was established on the basis of non-ionic gels thermodynamic model. The new model can be used to describe the change of lower critical solution temperature (LCST) of temperature-sensitive gels with the number of OH group in the gel. The predicted LCST agree reasonably well with experiment of PVDF-g-P(NIPA-co-GMA-Dex) gel LCST of PVDF hollow fiber membrane surface.