Perfluorinated sulfonic acid polymer

Using proton exchange membranes as electrolytes that are quasi-solid may cause a problem with respect to the perfect wetting of the catalyst particles. In spite of this (initial) difficulty of developing solid polymer membrane fuel cells, water-swollen perfluorinated sulfonic acid polymers such as the commercial Nation have been used for fuel cells very early since they offer the following advantages ... 

Nafion perfluorinated sulfonic acid polymer was imaged, showing a nodular structure with 45-nm spherical domains, which in turn contained 11-nm spherical grains. Interstitial pores in the polymer were found to contain lower densities of polymer, but were not completely void. The authors showed that a nonuniform... 

In perfluorinated sulfonic acid polymers there are relatively few fixed ionic groups. They are located at the end of side chains, so as to position themselves in their preferred orientation to some extent. Therefore, they can create hydrophilic nanochannels, so called cluster networks [Gierke and Hsu [22] and Gierke, Mimn and Wilson [23]]. 

Zhou, C., Guerra, M. A., Qiu, Z.-M., Zawodzinski, T. A., and Schiraldi, D. A. 2007. Chemical durability studies of perfluorinated sulfonic acid polymers and model compounds under mimic fuel cell conditions. Macromolecules 40 8695-8707. 

Between 1960 and 1980, the U.S. chemical company Du Pont de Nemours began delivery of ion-exchange membranes of a new type trade-named Naflon. They are made of a perfluorinated sulfonic acid polymer (PSAP) consisting of a continuous skeleton of —(CF2) -groups to which a certain number of hydrophilic... 

Perfluorinated sulfonic acid polymers, such as Nafion membranes, were the most commonly used materials in practical systems for their high proton conductivity and extremely high oxidative stability. However, due to the poor dimensional stability, low mechanical properties of Nafion at high humidity and high temperature, and high cost, an essential need for cost-effective and reinforced substitutes with improved performance arises [193-195]. Nafion blended with the second component could not only reduce the cost, but also improve the mechanical properties and the dimensional stability. Recently, the reinforced composite membranes based on semi-interpenetrating polymer network (semi-IPN) structures of Nafion , polyimidazole (PI) [196-198], polybenzimidazole (PBI) [199], and poly(vinyIidene fluoride) (PVDF) [200] were reported. As shown in Fig. 2.35, the composite membranes with... 

Nafion-H, a perfluorinated sulfonic acid resin, is another strongly acidic solid that has been explored as alkylation catalyst. Rprvik et al. (204) examined unsupported Nafion-H with a nominal surface area of 0.2 m2/g (surface area of a swellable polymer is difficult to define) in isobutane/2-butene alkylation at 353 K and compared it with a CeY zeolite. The zeolite gave a better alkylate and higher conversion than Nafion-H, which produced significant amounts of octenes and heavy-end products. The low surface area of the resin and questions about the accessibility of the sulfonic acid groups probably make the comparison inadequate. 

The most important use of /3-sultones is for the preparation of fluorinated polymers such as Nafion 64. These solid acid catalysts containing perfluorinated sulfonic acid groups have been known for many years and the presence of the electron-withdrawing F atoms increases the acid strength of the terminal sulfonic acid groups, which become comparable to that of pure sulfuric acid. Prior to the last decade, Nafion had been in use as a superacid, a fuel cell electrolyte and as a membrane-ion separator <1996CHEC-II(1B)1083>. 

A convenient solid of perfluorinated-sulfonic acid can be made readily from DuPont s commercially available Nafion brand ion membrane resins. Powder granules of the 1200-EW polymer, Nafion 501, have been used most frequently in catalytic applications the price in the K+ form of the perfluorosulfonic salt, 501X, was 650/kg in 1981. Because only the potassium salt derivative is commercially available, the salt is converted to the free sulfonic acid by treatment with mineral acid. A standard procedure for the conversion is described below. This procedure also serves to regenerate the resin in various catalytic cycles. 

The PEFC was first developed for the Gemini space vehicle by General Electric, USA. In this fuel cell type, the electrolyte is an ion-exchange membrane, specifically, a fluorinated sulfonic acid polymer or other similar solid polymer. In general, the polymer consists of a polytetrafluoroethylene (Teflon) backbone with a perfluorinated side chain that is terminated with a sulfonic acid group, which is an outstanding proton conductor. Hydration of the membrane yields dissociation and solvation of the proton of the acid group, since the solvated protons are mobile within the polymer. Subsequently, the only liquid necessary for the operation of this fuel cell type is water [7,8],... 

Nafion, a perfluorinated sulfonic acid (PFSA) polymer electrolyte developed and produced by the E. I. Dupont Company, has been extensively studied as a fuel cell membrane. Despite its age, it remains the industry standard membrane because of its relatively high proton conductivity, toughness and quick start capabilities. Attempts to build upon the strengths of Nafion have resulted in a class of PFSA polymer electrolytes, including the short-side-chain (SSC) PFSA polymer electrolyte, originally synthesized by Dow and now produced by Solvay Solexis. Stracturally, PFSA polymer... 

The majority of solid proton-conducting membranes, most commonly used in contemporary fuel cell technology, are hydrated perfluorinated sulfonic acid ionomers. In recent years, enormous programs in membrane research have explored empirically how various modifications of the benchmark material, viz. Nafion, affect the physical membrane properties. The main modifications include (1) varying the hydrophobic/hydrophilic composition of the polymer, (2) controlling the grafting density and lengths of the sidechains,... 

The most frequently used polymer membranes are proton conducting polymers of the perfluorinated sulfonic acid (PFSA) type, the most well known being Nafion from DuPont. A review on the state of understanding has been given by Mauritz and Moore [10]. A section of Nations chemical formula is given in Fig. 14.4. 

Wang et al. [184] reported a new class of iono-mers with rigid aromatic backbone (based on PAE, poly(ether ether ketone) (PEEK), poly(ether ether sulfone) (PEES), and poly(p-phenylene)) and pendant perfluorinated sulfonic acid groups. Scheme 2.51 shows a few representative PAE structures. The oxidative stability of the polymer membranes... 

Inaba M (2009) Chemical degradation of perfluorinated sulfonic acid membranes. In Buechi EN, Inaba M, Schmidt TJ (eds) Polymer electrolyte fuel cell durability. Springer, New York... 

Perfluorinated sulfonic acid containing polymer (PFSA)... 

Perfluorinated sulfonic acid containing polymers (PESAs) are the most commonly used membrane materials in fuel cells today. Membranes made from these ionomers provide the benefits of highly acidic pendant acid groups for high proton conductivity, good mechanical properties, excellent chemical stability, and fairly... 

---