The preparation of porous proton exchange membranes via in situ polymerization

• A novel porous PVDF-g-PSSA membrane was prepared via phase inversion and in situ solution-grafting methods.
• The phase separation could be controlled with in situ polymerization methods.
• The PVDF-g-PSSA membrane had low swelling ratio and high proton conductivity.

A novel poly(vinylidene fluoride)-graft-poly(styrene sulfonic acid) (PVDF-g-PSSA)–based proton exchange membrane (PEM) was prepared by phase inversion and a grafting method in solution. Polystyrene was successfully grafted onto the surface and into the pores of the PVDF membrane, and the membrane was subsequently treated in a KOH ethanol solution. A linear relationship was observed between the degree of grafting and the treatment time in KOH solution. Fourier transform infrared spectroscopy and scanning electron microscope were used to characterize the changes in the membrane’s microstructure after grafting and sulfonation. Thermogravimetric analysis was used for evaluating the thermostability of the membrane. In addition, the proton conductivity of the solution-grafted PVDF-g-PSSA membrane was found to reach 0.13 S cm− 1 at 80 °C.