Investigation on sulfonated PVC/polymethyl methacrylate (PMMA)/polystyrene sulfonate (PSS) polymer blends as proton-conducting membrane

The design and development of cost-effective and increased methanol permeable and proton-conductive membranes are critical concerns in the fabrication of polymeric electrolyte membranes (PEM). A solution-casting process was used to create a low-cost PEM based on sulfonated polyvinyl chloride (SPVC)-Polymethyl methacrylate (PMMA) blended with varying concentrations of Poly(sodium 4-styrenesulfonate) (PSS). The contact angle, oxidative stability, swelling ratio, water uptake, and methanol uptake of SPVC/PMMA/PSS membranes were investigated as a function of PSS molar ratio. FT-IR examination, 1H NMR spectra, Raman spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), and scanning electron microscope micrographs were additionally utilized for confirming the chemical structure, morphology, and thermal stability of SPVC/PMMA/PSS membranes. Furthermore, the ion exchange capacity (IEC), proton conductivity, and methanol permeability of SPVC/PMMA/PSS membranes were investigated depending on the PSS concentration. The results showed a significant increase in proton conductivity from 1.80 x 10-2 for SPVC/PMMA/1%PSS to 4.7 x 10-2 S/cm for SPVC/PMMA/5%PSS at ambient temperature. On the other hand, the methanol permeability (P = 8.53 x 10-8 cm2/s) was noticeably lower than that of Nafion 117 (3.39 x 10-6 cm2/s). Additionally, the IEC of the manufactured membrane was 1.38 +/- 0.7 meq g-1 for SPVC/PMMA/5%PSS compared to 0.91 meq g-1 for Nafion 117 membranes. The maximum water uptake of the synthesized membranes was 48.37 +/- 2.27%, whereas Nafion 117 membrane absorption was 65.44%. According to conductivity studies and the membrane efficiency factor, the ideal PSS content in a polymer matrix is 4 wt.%. Finally, the developed SPVC/PMMA/PSS polyelectrolytic membranes show improvements in essential properties such as methanol permeability, proton conductivity, and IEC when combined with low-cost materials, making them an attractive contender as PEM for DMFCs.