Controllable sulfonation of aromatic poly(arylene ether ketone)s containing different pendant phenyl rings

Abstract

The sulfonation selectivity of various pendant phenyl groups in poly(arylene ether ketone) (Ph-3F-PAEK) is invested via the postsulfonation approach. The sulfonated Ph-3F-PAEKs with different degrees of sulfonation (DS) are quantitatively synthesized by controlling the length of the segments that cannot be sulfonated. In this study, 1H NMR and FT-IR are used to confirmed the structures of the polymers and the experimentally DS values were calculated by 1H NMR. The experimentally observed DSs are corresponding to the theoretical values expected from the monomer ratios. All the sulfonated membranes have excellent mechanical properties (with a Young's modulus >1.3 GPa, a tensile strength >55 MPa and the elongation >10%). Thermogravimetric analysis (TGA) is used to characterized the thermal stability of these polymers, and all the polymers show excellent thermal properties at high temperatures. The methanol permeability values of Ph-3F-SPAEKs in the range of 0.37 × 10−7 cm2 s−1 to 4.12 × 10−7 cm2 s−1 are much lower than that of Nafion® 117 (1.55 × 10−6 cm2 s−1). It should be noted that the polymer with highest DS, Ph-3F-SPAEK-100 with an ion exchange capacity of 2.16 mequiv. g−1, exhibits high proton conductivity of 0.187 S cm−1 at 80 °C, which is also higher than that of Nafion® 117.