The work concerns new polymeric materials for electrolytes synthesized at the Electrotechnical Institute. Poly(styrene-4-sulfonate)-grafted poly(vinylidene fluoride) (PVDF-gPSSA) membranes proton-exchange membranes were synthesised by free radical graft polymerization of polystyrene into PVDF films (50 mu m thick) followed by sulfonation. Physical and electrochemical properties of that membranes were investigated. The membranes were tested as electrolytes in a single cell-configuration system. The influence of working condition, as gas humidity and cell temperature on fuel cell performance were measured. Obtained performances were lower in comparison with commonly used electrolyte materials. At this stage of development the synthesized materials are not suitable for fuel cell application. The results gave authors information for selection membrane with the best parameters and chemical process configuration.