Structural investigation of radiation grafted and sulfonated poly(vinylidene fluoride), PVDF, membranes

Abstract

Radiation grafted and sulfonated poly(vinylidene fluoride), PVDF, membranes have been studied by thermal analysis and X-ray diÂraction to determine the changes in membrane crystallinity and structure during preparation. Commercial PVDF films were irradiated with an electron beam, grafted with styrene and finally sulfonated. Both the crystallinity and the size of the crystallites of PVDF decrease in the grafting reaction. A further decrease in crystallinity is observed in the sulfonation reaction. The residual crystallinity of PVDF was considerable (10-20%) even in membranes which had been subjected to severe reaction conditions. These results can be explained by assuming that the grafting takes place mainly in the amorphous region of the PVDF, and close to the surfaces of the crystals, but that grafts do not penetrate into the crystals. The proton conductivity of the grafted and sulfonated PVDF membranes reached values comparable to those of Nafion membranes.

Phase separation and crystallinity in proton conducting membranes of styrene grafted and sulfonated poly(vinylidene fluoride)

“…Because of incompatibility of polystyrene and PVDF, the grafts form phase separated regions, which are further reorganized in the following sulfonation reaction. 15,16 To further study the influence of crosslinking on the structure of the membranes, their crystallinity was determined. The inherent crystallinity of the PVDF decreases in the grafting process in the absence of crosslinkers and decreases further during the sulfonation.…”

“…The inherent crystallinity of the PVDF decreases in the grafting process in the absence of crosslinkers and decreases further during the sulfonation. 16 The crystallinity of the crosslinked membranes was evaluated from results of thermal analysis differential scanning calorimetry, (DSC), and from wide-angle X-ray diffraction measurements (WAXS). In the thermal analysis the crystallinity was calculated from the enthalpies of fusion.…”

“…The preparation involves the preirradiation of the PVDF film with electron beam, graft polymerization of styrene into the matrix, and sulfonation of the grafted film. 15 The characterization of these membranes involved thermal analysis, X-ray diffraction [wide-angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS)] measurements, 16 and electrochemical analysis. 17 Preliminary fuel cell tests show promise for the development of these membranes.…”

Approaches and Recent Development of Polymer Electrolyte Membranes for Fuel Cells Operating above 100 °C

“…153 Poly(vinylidene fluoride)-(PVDF) based polymer membranes have also been prepared by grafting and then sulfonating the styrene groups, mainly by Sundholm's group. [154][155][156][157][158][159][160][161][162] The combination of the good physical stability and chemical resistance of PVDF with the good conductive properties of sulfonated polystyrene seems to give high water uptake 158 and high proton conductivity. [155][156][157] Partially fluorinated polymer membranes based on R, , -trifluorostyrenes have been prepared by either sulfonation 163 or phosphonation.…”

Selectivity of Acrylic Acid Radiation Grafted Non-Woven Polypropylene Sheets towards Some Heavy Metals Ions

“…This is due to dilution of the crystal line fraction by the incorporation of the amorphous PAAc chains into the polymer matrix. It can be concluded that the graft polymerization took place predominantly on the polymer film surface of the crystallites progressed inward thus breaking up partly ordered chain structures of the NWPP matrix [21].…”