Radiation grafted membranes: some structural investigations in relation to their behavior in ion-exchange-membrane water electrolysis cells

Radiation-induced grafting of styrene onto poly(tetrafluoroethylene) (PTFE) films. I. Effect of grafting conditions and properties of the grafted films

“…The shift in the binding energy of CF 2 from that of CH 2 reported in the literature is due to the chemical shift arising from the electron attraction towards the fluorine atoms, which equals 8 eV. Such results are in good agreement with those obtained by Scherer et al 38 upon investigation of some radiation‐grafted commercial membranes such as Permion 4010 and 5010 (RAI Inc, Hauppauge, NY, USA). The F/C ratio is found to be 2.09, which is in a good agreement with the theoretical value of 2.…”

Part II. Properties of the grafted and sulfonated membranes

“…This was accompanied by a very small peak at 293.2 eV (FWHM 1.3 eV) representing the fluorinated domain in the membrane matrix. The separation of the two peaks by 7.3 eV is in complete agreement with the difference in binding energy between CH 2 of polyethylene and CF 2 of polytetrafluoroethylene as reported by Scherer et al 38 Deconvolution of the spectrum results in five peaks at 292.1, 287.5, 286.5, 285.2 and 284.5 eV (corrected), which were assigned to CF 2 , CS, CCF, C and C, respectively. The emergence of the peak at 287.5 eV is due to the attachment of the sulfonic acid groups to the benzene ring of polystyrene, which led to further decrease in the F/C ratio from 0.26 in the grafted PTFE film to 0.066.…”

Proton‐exchange membranes by radiation grafting of styrene onto FEP films. II. Mechanism of thermal degradation in copolymer membranes

“…The first stage (desulfonation) must involve H abstraction, presumably from a neighboring sulfonic acid group as depicted in I, resulting in a cross-linked sulfonate-bridged intermediate structure ( 11). The stoichiometry of the evolved products is formally equivalent to sulfurous acid, H2S03, but this compound, if formed, would be expected to decompose rapidly at 350°C to yield simultaneously SO2 and H20, as observed in Figure 6.…”