Synthesis and Properties of Sulfonated Poly(arylene ether)s with Flexible Oligomeric Phenylene Ether Segments

Abstract

Novel sulfonated poly(arylene ether)s derived from ω,ω′-dihydroxypoly(1,4-phenylene ether)s (DHPE) and mixed dihalide monomers of 3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (S-DCDPS) and 2,6-dichlorobenzonitrile were synthesized. As DHPE has molecular weight distribution with phenylene rings lower than ca. 10 units, experimental determination of its average molecular weight made it possible to be used as a monomer to prepare sulfonated poly(arylene ether)s. Membranes derived from resultant polymers showed a similar level of proton conductivity to those of other common sulfonated poly-(arylene ether)s; however, its softening temperature was much lower. Therefore, good MEA was able to be obtained by hotpressing at relatively lower temperature without shrinking around electrode. The membrane with an ion exchange capacity of 0.9 showed lower methanol permeability and dimensional change in methanol solution assuming a condition of DMFC than standard perfluorosulfonic acid polymer membrane (PFSA). ■ INTRODUCTIONSolid polymer electrolyte membrane fuel cell (PEMFC) is attracting much attention as a new power source for transportation, stationary, portable, and consumer electronics power applications from the viewpoint of environmental and new energy issues. Polymer electrolyte membranes (PEM) made of sulfonic acid-containing aromatic condensation polymers are considered as possible candidates for an alternative of perfluorosulfonic acid polymers (PFSA) membrane, such as Nafion, because their backbone structures are generally heat-and solvent-resistant with good mechanical properties. 1−3 Although PFSA showed much higher stability against radical oxidation and has been used as a standard membrane material for PEMFC, accumulation of studies for sulfonated aromatic condensation polymers may create new characteristic materials.Sulfonic acid-containing aromatic condensation polymers are considered as essentially good structure for especially direct methanol fuel cell (DMFC) because they are stable against hydrolysis and show relatively low methanol permeability. Sulfonated polymers derived from poly(arylene ether ketone)-s, 4−6 poly(arylene ether sulfone)s, 7−10 poly(arylene thioether)-s, 11 other poly(arylene ether)s, 12−14 polyimides, 15−18 poly-(phenylene)s, 19 and other types of polymers have been extensively studied so far. As methanol crossover from anode to cathode induces decrease in fuel efficiency and reduction of cell voltage, these aromatic condensation polymer shows a great advantage against PFSA membrane. Although their performance of polymer electrolyte membrane is highly expected in this point of view, drawback in the processability to prepare membrane−electrode assembly (MEA) exists. As MEA is usually prepared by hot-pressing of membrane with electrode containing PFSA ionomer as a binder, high glass transition temperatures of aromatic condensation polymers sometimes result in poor adhesion between them. The poor adhesion does not only induce difficulty to prepare good MEA but also increases in ME...

Effect of platinum loading on fuel cell cathode performance using hydrocarbon ionomers as binders

“…In the literature, there are a number of candidates, including aromatic polymers, aliphatic polymers, ionic liquids, organic/inorganic hybrid compounds, etc. [1][2][3][4][5][6] Some of these materials have been claimed to show comparable or even better performance compared with PFSAs when used as the electrolyte membrane. However, not much research has been done on the use of these emerging ionomers as electrode binders.…”

Synthesis and properties of sulfonated poly(arylene ether ketone sulfone) copolymer

“…It is proved that the flexible ether bond between two phenylenes showed lower softening temperature. 27 Therefore, good membrane electrode assembly (MEA) was obtained by hot pressing at relatively lower temperature without shrinking around electrode. This series of sulfonated copolymers exhibited good solubility in polar aprotic solvents such as DMSO, DMAc, dimethylformamide (DMF), and N -methylpyrrolidone.…”

Nanofiltration Hollow Fiber Membranes Made from Sulfonated Polysulfone having a Cyanophenylene Group

“…The range of concentration was adjusted from 30 to 40 weight percent. The method for synthesis and polymerization of the polymer is shown in the literature [4]. To make an inner hole of the hollow fiber, a liquid was injected into the center of the concentrated solution that was also extruded in a spinneret with a pump.…”

“…As one may imagine, the high content of sulfonate groups in the molecule, going over a certain level, may give higher flux of water, but it may also form a very soft membrane that cannot keep even its own shape as membranes and the resultant structure would dissolve *Address correspondence to this author at the Membrane-Structural Development Group, Toyobo Co., Ltd, Research Center, 2-1-1 Katata, Otsu, Shiga 520-0292, Japan; E-mail: Tooru_Kitagawa@toyobo.jp in water. To overcome these disadvantages we put a cyanophenylene group in the molecular structure of sulfonated polysulfone, shown in Figure 1 [4]. This would induce strong inter-molecular interactions to make dense and network structures of sulfonated polysulfone in the membrane down to the nanoscale level.…”