Table 2 lists the water uptake of the six OH form membrane samples. The test method was described in Section 2.6. The water uptake of ionic exchange membranes reflects the hydrophilicity of the membranes because of the strong hydrophilicity of the imidazolium salt. Thus, it can be observed that the water uptake of the membrane increases with the increase of the imidazolium cation group content in the membrane. Membrane D shows a water uptake of 82.7% with the highest content of imidazolium cation groups.