Proton transport properties of sulphanilic acid tethered poly(methyl vinyl ether-alt-maleic anhydride)-PVA blend membranes

•Sulphonated hydrocarbon proton exchange membranes were synthesized and characterized.•These were based on sulphanilic acid tethered poly(methyl vinyl ether-alt-maleic anhydride).•The presence of nanopores in membrane was confirmed by SEM and AFM analyses.•The values of conductivity and proton diffusivity of the membrane was 0.0045 S/cm and 10−10 m2/s.•Statistical analyses provide the understanding of the obtained electro-chemical properties.

This work is an effort to demonstrate a simple approach to develop sulphonated hydrocarbon proton exchange membranes with randomly oriented and distributed pores that are suitable for separation and fuel cell applications. Sulphanilic acid (SA)-tethered poly(methyl vinyl ether-alt-maleic anhydride) (sPMVEMA) was synthesized and characterized using FTIR and 1H NMR. As the synthesized neat polymer lacked the membrane-forming property and was also water soluble, it was thought to physically blend the same with poly(vinyl alcohol) (PVA). The nanoporous proton exchange membranes were cross-linked with gluteraldehyde (GA). Further, ATR-FTIR spectra confirmed the cross-linking of the membranes. The TGA analysis showed the stability of blend membranes up to 300 °C, suggesting a beneficial effect of PVA for ∼50 °C. Likewise, analysis of the surface morphology using SEM, AFM and TEM images showed micro-level immiscibility between the polymers, sPMVEMA and PVA. This resulted in confirming nano-porosity in the membrane. The ion exchange capacity (IEC) and water uptake showed linear dependency on the weight fraction of sPMVEMA in blended membrane. The obtained water diffusion coefficient values increased with increase in weight fraction of the sPMVEMA in blend membranes. The membrane conductivity was measured at different proton concentrations and found to be 0.0045 S/cm at 0.1 M [H+] for 0.5 weight fraction of sPMVEMA with 75% SA modification. The diffusion coefficients were calculated using the iso-conductance method and found to be of the order of 10−10 m2/s, compared to that of reported values in literature. Statistical evaluation was made to analyze and understand the obtained electro-chemical properties.

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