Aruna Kumar Mohanty

Proton exchange properties of flexible diamine-based new fluorinated sulfonated polyimides

A series of new semifluorinated sulfonated polyimide copolymers (DHNHXX) were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 4,4′-diaminostilbene-2,2′-disulfonic acid (DSDSA) and 1,4-bis-[{2′-trifluoromethyl-4′-(4′′-aminophenyl)phenoxy}] benzene (HQA). The degree of sulfonation of DHNHXX was varied by changing the molar ratio of the sulfonated diamine, DSDSA to the non-sulfonated diamine, HQA. The flexible DHNHXX membranes showed high thermal stability (desulfonation temperature above 270 °C) and good mechanical properties. The oxidative stability of DHNHXX improved with increasing the fluorine content. DHNHXX showed anisotropic dimensional changes, and good water stability (did not dissolve for up to 415 h), higher than many other sulfonated polyimides. Transmission electron microscopy (TEM) analysis revealed cluster-like microstructures for the DHNHXX membranes, suggesting good phase-separated morphology. DHNH70 with IEC = 2.10 meq. g−1 exhibited high proton conductivity, with a maximum up to 129 mS cm−1 at 90 °C in water.

Fluorinated Poly(Arylene Ether)s: Synthesis, Properties, and Applications

Abstract Poly(arylene ether)s consisting of aromatic rings and ether linkages form an important class of high-performance polymeric material with an excellent combination of thermal and mechanical properties. Poly(ary1ene ether)s are generally synthesized via nucleophilic aromatic substitution of an activated dihalide with an aromatic bisphenol. Fluorinated poly(arylene ether)s containing bulky –CF 3 groups are especially interesting because they enhance the solubility of the polymers and increase the glass transition temperature without reducing thermal stability. The bulky –CF 3 group also serves to increase the free volume of the polymer, thereby improving various properties of the polymer including its application as a membrane material and in microelectronic applications by endowing a low dielectric constant. The first part of the chapter deals with the synthetic strategies, characterization, and general properties of fluorinated poly(arylene ether)s. The second part deals with the application of fluorinated poly(arylene ether)s in gas separation and pervaporation and as proton exchange membranes for fuel cell application.