Preparation Of Net-shaped Microporous PVDF Membrane And Its Application On Western-blotting

In this dissertation, symmetric poly-(vinylidene fluoride) (PVDF) membranes were prepared both by dry-cast process and immersion-precipitation process, which have the unique structure of net-shape without dense skin layer. Therefore it could be used as protein-blotting membranes for its strong non-specific adsorption ability of protein.First, the membranes formation containing PVDF/N,N-Dimethylacetamide (DMAc) by dry-cast process was studied. Membrane morphologies from crystalline polymers were found to be strongly dependent on the evaporation temperature and relative humidity. The net-shaped membrane without the dense skin layer on the air surface were obtained at the temperature of 45℃ and relative humidity (RH=90).By adding gasified DMAc in the evaporation atmosphere, the skinless membrane could be ulteriorly gained. The results indicated that the solidification of the membrane could be achieved through the competition of gelation and crystallization. The effect of the addictives on the membrane formation was further investigated. By adding LiCl in the cast solution, the membrane prepared can have an adsorption of protein for 15μg·cm^-2.Secondly, the membranes formation containing PVDF/Triethyl phosphate (TEP) by immersion-precipitation using two successive coagulation baths was studied. In this system, the net-shaped pores replaced the finger-like pores. It was found that the morphology of PVDF membranes was greatly influenced by its molecular weight. The global crystal disappeared with PVDF of lower molecular weight. Dense layer would appear using pre-evaporation process, indicating it's not a proper process to prepare protein-blotting membrane. The dense layer disappeared with the increase of TEP concentration in the firstTEP/water bath, and extending of the reaction time leads to the increased mean pore diameter. Low temperature of two baths tend to decrease the porosity of membranes and turn crystal type from a form to β form, which can greatly enhance the adsorption ability of protein. The study above indicated that liquid-liquid demixing takes place early and determined the final structure of PVDF membrane, whereas solidification of the membrane determined the overall crystallinity and crystal type of PVDF membranes.The PVDF membrane obtained by immersion-precipitation was tested in western-blotting application and reveals a good result which is similar to that of PVDF membrane produced by Millipore Company.