Comparison of PEM Properties of Copoly(aryl ether ether nitrile)s Containing Sulfonic Acid Bonded to Naphthalene in Structurally Different Ways

Abstract

The study represents a comparative investigation of three series of high molecular weight aromatic poly(aryl ether ether nitrile) copolymers (SPAEEN-n), containing different sulfonated naphthalene groups, where n (in the range 0-80 mol %) refers to molar percentage of repeat units containing the sulfonic acid function. The three series of SPAEEN-n copolymers were synthesized via potassium carbonate-mediated nucleophilic polycondensation reactions of commercially available monomers: 2,6-difluorobenzonitrile (2,6-BFBN), one of three dihydroxynaphthalenesulfonate (DHNS) monomers, and unsulfonated 4,4′-biphenol (BP), incorporated for the purpose of adjusting the sulfonic acid content. The incorporation of the sulfonated repeat unit into copolymers and their structures were confirmed by 1 H NMR and FT-IR spectroscopy. Products were solvent-cast into membranes of varying ionic content as proton exchange membrane (PEM) materials for fuel cells applications. Ion exchange capacity (IEC), thermal stabilities, swelling, and proton conducting properties of the membranes were investigated in relation to their structures and compared with those of perfluorinated ionomer (Nafion 117). Films of SPAEENH copolymers in acid form all showed high thermal stabilities with glass transition temperatures (T g ) > 224°C and decomposition temperatures (T d ) > 264°C. In general, the SPAEENH copolymers exhibited low moisture absorption and in some instances high proton conductivities (from 10 -2 to 10 -1 S/cm) comparable to that of Nafion 117 at similar water uptake, swelling, and H 2 O/SO 3 H ratio.

Sulfonated hydrocarbon membranes for medium-temperature and low-humidity proton exchange membrane fuel cells (PEMFCs)

“…The researchers also performed a comparative study of sulfonated poly(arylene ether ether nitrile) (SPAEEN) copolymers with different sulfonic acid bonding sites (Fig. 15) [87][88][89][90], which will be further discussed in Section 2.2.1.…”

Polymer Electrolyte Membranes Derived from New Sulfone Monomers with Pendent Sulfonic Acid Groups

“…[4][5][6] Consequently, much progress has been made to develop novel hydrocarbon PEMs based on sulfonated aromatic polymers, which have good physical properties and are inexpensive. The most widely investigated PEMs include sulfonated derivatives of poly(arylene ether sulfone)s (SPAES), 7,8 poly-(arylene ether ether ketone)s (SPEEK), [9][10][11] poly(arylene sulfide sulfone)s (SPSS), 12,13 poly(arylene ether nitrile)s (SPAEEN), [14][15][16] polyimides (SPI), [17][18][19][20][21] and polyphenylenes (PP). [22][23][24] Many hydrocarbon polymers show sufficiently high conductivities only at high ion-exchange capacities (IEC)s, which causes extensive water uptake above a critical temperature (percolation threshold), or a dramatic loss of mechanical properties due to dimensional swelling that render them unsuitable for practical PEM applications.…”

Comparative effect of phthalazinone units in sulfonated poly(arylene ether ether ketone ketone) copolymers as proton exchange membrane materials

“…Chemically and thermally stable fully aromatic hydrocarbon polymers containing pendant acidic functions are considered promising as alternative PEM materials. 2 Among recently developed polymer electrolyte membranes, sulfonated poly(arylene ether sulfone) (SPAES) and sulfonated poly(arylene ether ketone) (SPAEK) are promising. [3][4][5][6][7][8][9] Wang et al 9 reported the synthesis of biphenyl-based SPAES.…”