Fabrication and characterization of electrospun sulfonated poly(phthalazinone ether ketone) mats as potential matrix of reinforced proton exchange membranes

Abstract

In this paper, the sulfonated poly(phthalazinone ether ketone) (SPPEK) nanofibers with low sulfonation degree are fabricated by electrospinning for the first time. The optimized concentration of SPPEK for electrospinning is 0.16 g ml 21 and the suitable solvent is the mixture of DMAc and NMP. The resulting SPPEK nanofibers show smooth surfaces and uniform diameters of about 50 nm. Proton conductivities of the SPPEK mat and membrane are tested and compared. The result indicates that the proton conductivity of the SPPEK mat is almost five times as high as that of the SPPEK membrane because of the formation of long-range proton pathways on the surfaces of SPPEK nanofibers.

Conductivity of composite membrane-based poly(ether-ether-ketone) sulfonated (SPEEK) nanofiber mats of varying thickness

“…These results are in agreement with the literature, 62,64 where it is found that the proton conductivity of SPEEK nanober mat is nearly ve times as high as that of the SPEEK composite membrane. Our result is also consistent with the work of Hongwei et al, 62 where two possible pathways are presented: (1) the long-range proton conductivity pathways are formed inside of the nanobers, 65 and (2) the long-range proton conductivity pathways are formed on the surfaces of the nanobers.…”

“…From these results, we can observe that the proton conduction mechanism is more efficient through the surface of the SPEEK-PVB nanobers than through the matrix of SPEEK-PVA; similar results have been observed in other nanocomposites. 61,62 On the other hand, it is possible to observe a critical thickness as a function of the electrospinning time (M-12 with 12 hours of electrospinning time of SPEEK-PVB) where the protonic conductivity is the highest, as shown in Fig. 5a.…”

Nanocomposite SPEEK-based membranes for Direct Methanol Fuel Cells at intermediate temperatures

“…Then, apparently, reduction of surface concentration of water molecules and sulfonic acid groups on the SPEEK-30%PVB nanofibers strongly affects their conductivity properties as a consequence of a more limited proton conduction via the water-sulfonic acid association. This conclusion about conductivity preferentially taking place on the nanofibers surface would be in agreement with those reported in other studies [32,63]. Moreover, this explanation can be supported by the fact that nanofiber axis orientation is perpendicular to the proton conduction direction, which might difficult conductivity through the nanofiber bulk but on the nanofiber surface.…”

“…Two proton conduction mechanisms associated to the nanofiber morphology could explain this large increment of proton conductivity. On one side, conductivity may be improved through the bulk due to an induced preferential orientation of the ionic channels along the nanofiber axis, and on the other side, conductivity may be encouraged on the nanofiber surface through the strong interface formed between water molecules and external sulfonic acid groups [32].…”

“…Higher increment of the proton conductivity is observed along the fiber axis direction than perpendicularly, which is attributed to the preferential orientation of the sulfonated polymeric chains and the consequent alignment of the ionic channels [21,22]. On the other hand, it has been suggested that proton transport takes place preferentially on the surface of the nanofibers, enriched with ionic clusters, rather than inside the nanofiber structure [32]. Probably, a plausible explanation for the enhancement of the proton conductivity of polymer electrolyte nanofibers involves both mechanisms.…”