Materials Concentration of chlorosulfonic acid Young’s modulus(MPa) Tensile strength (MPa) PET-g-PSSA 0.2 3566 ± 23 60.7 ± 1.2 0.5 2115 ± 34 41.5 ± 1.1 0.7 1037 ± 40 8.6 ± 1.3 1 677 ± 30 7.2 ± 1.2 Nafion NR212 --- 368 ± 26 29 ± 1.1

Table 1: The mechanical parameters for Nafion and PET-g-PSSA with degree of grafting 166 prepared from different concentration of chlorosulfonic acid.