Synthesis and characterization of fluorinated and sulfonated poly(arylene ether-1,3,4-oxadiazole) derivatives and their blend membranes

Perfluoro-p-xylene as a New Unique Monomer for Highly Stable Arylene Main-Chain Ionomers Applicable to Low-T and High-T Fuel Cell Membranes

“…According to Figure 2, the thermal stability of the sulfonated products 3 and 4 is lower than that of the non-sulfonated polymers. A similar observation has been made for other arylene main chain polymers [12]. TGA-FTIR coupling experiments showed clearly that the sulfonated polymers split off -SO3H starting at 317 °C for 3 and 241 °C for 4.…”

“…The thermal stability of 4 is almost 80 °C lower than that of 3, although 4 has higher fluorine content than 3, as already shown in the literature, that partially fluorinated aromatic polymers are more stable than their non-fluorinated analogues [7]. On the other hand, it has been found that the polymer stability can decrease if the aromatic system is too electron-deficient, as in the case for highly fluorinated oxadiazole polymers synthesized recently in the authors' group [12].…”

“…The structure of the sulfonated polymers was determined by showing similar values as has been presented in previous work [12]. The integration of the peaks of 4 was used to determine the number of protons.…”

“…Due to the weak signals despite the high concentration, the exact position of the -SO3H groups could not be confirmed by heteronuclear single-quantum correlation measurements. According to the literature, it is expected that the SO3H group is introduced in the ortho position next to the ether-group [12,13].…”

“…The integral ratio between the signals of the sulfonated and non-sulfonated units at the same position can be used to determine the sulfonation degree [12,13]. PFX is incompletely two-fold sulfonated, and all three degrees of substitution of the biphenyl unit can coexist in the polymer backbone (non-sulfonated, one-fold sulfonated and two-fold sulfonated).…”