Membranes perfluorosulfonate ionomer

A.A. Karyakin, E.A. Kotel nikova, L.V. Lukachova, E.E. Karyakina, and J. Wang, Optimal environment for glucose oxidase in perfluorosulfonated ionomer membranes improvement of first-generation biosensors. Anal. Chem. 74, 1597—1603 (2002). 

The earliest concerted effort in the research and development of Nafion perfluorosulfonate ionomers was directed toward their use as a permselective membrane separator in electrochemical cells used in the large scale industrial production of NaOH, KOH, and CI2. In short, the membrane in this application, in addition to keeping CI2 and H2 gases separated, prevents the unfavorable back migration of hydrated OH ions from the catholyte (concentrated aqueous NaOH or KOH) chamber, while allowing for the transport of hydrated Na+ ions from the anolyte chamber in which is aqueous NaCl. 

Composites between polypyrrole and a variety of porous materials such as paper, cloth or wood have been made. Often the respective material was impregnated with an oxidant such as FeCls and subsequently contacted with pyrrole vapor or solution. For example, polypyrrole (and polyaniline) have been made in Nafion perfluorosulfonated ionomer membranes by treatment with aqueous ferric chloride and the monomers. ... 

Yamaguchi T, Koval CA, Noble RD, and Bowman CN. Transport mechanism of carbon dioxide through perfluorosulfonic ionomer membranes containing an amine carrier. Chem. Eng. Sci. 1996 51 4781 789. 

E.E. Boakye and H.L. Yeager. Water sorption and ionic-diffusion in short side-chain perfluorosulfonate ionomer membranes. Journal of Membrane Science 69, 155-167 1992. 

The water distribution within a polymer electrolyte fuel cell (PEFC) has been modeled at various levels of sophistication by several groups. Verbrugge and coworkers [83-85] have carried out extensive modeling of transport properties in immersed perfluorosulfonate ionomers based on dilute-solution theory. Fales et al. [109] reported an isothermal water map based on hydraulic permeability and electro-osmotic drag data. Though the model was relatively simple, some broad conclusions concerning membrane humidification conditions were reached. Fuller and Newman [104] applied concentrated-solution theory and employed limited earlier literature data on transport properties to produce a general description of water transport in fuel cell membranes. The last contribution emphasizes water distribution within the membrane. Boundary values were set rather arbitrarily. 

An adequate structure of polymer molecules promotes the advantageous phase separation into hydrophobic and hydrophilic domains upon water uptake. The most notable class of membranes based on this principle are the perfluorosulfonic acid ionomers (PFSI), Nafion [26] and similar membranes [27]. In these membranes, perfluorosulfonate side chains, terminated with hydrophilic —SO3H groups, are attached to a hydrophobic fluorocarbon backbone. The tendency of ionic groups to aggregate into ion clusters due to the amphiphilic nature of the ionomer leads to the formation of basic aqueous units. At sufficient humidity these units first get connected by narrow channels and then may even fuse to provide continuous aqueous pathways [28]. 

Perfluorosulfonate Ionomers Nafion Dupont Multiple membrane uses... 

In a another study (.8), we have analyzed the literature data associated with our SANS data and shown that the scattering data on perfluorosulfonated ionomer membranes are consistent with the scattering produced by a group of hard spheres dispersed in the polymeric matrix. The number of ions per cluster was found to change with the water absorption values, with the cation, and with equivalent weight. The occurence of the scattering maxima is due to interference effects between clusters. Further calculations have to be made to take into account a possible anisotropy of these ionic spheres. 

R. Schlogl and F. Helfferich, Theory of exchange membrane potentials, Z. Elektro-chem, 1952, 56, 644-647 N. Ishibashi, T. Seiyama and W Sakai, Electrochemical studies on ion exchangers (Part 10) Mobilities of Ca+ and Cl- in the cation exchange membrane, Denki Kagaku (J. Electrochem. Soc. Jpn.), 1955, 23, 182-186 E.E. Boakye and H.L. Yeager, Water sorption and ionic diffusion in short side chain perfluorosulfonate ionomer membranes, J. Membr. Sci., 1992, 69, 155-167. 

T.T. To, R.D. Noble and C.A. Koval, Effect of protonation on the transport of hydrophobic nitrogen heterocycles through perfluorosulfonate ionomer membranes, J. Membr. Sci., 1992, 75, 293-297. 

T.D. Gierke and W.Y. Hsu, The cluster-network model of ion clustering in perfluorosulfonated membranes, Perfluorinated Ionomer Membranes, ACS Symposium Series, ed. A. Eisenberg and H.L. Yearger, American Chemical Society, Washington D.C., 1982, Vol. 180, pp. 283-307. 

Z.D. Deng and K.A. Mauritz, Dielectric relaxation studies of acid-containing short-side-chain perfluorosulfonate ionomer membranes, Macromolecules, 1992, 25, 2369-2380. 

E.J. Roche, M. Pineri and R. Duplessix, Phase separation in perfluorosulfonic ionomer membrane, J. Polym. Sci., Polym. Phys. Ed., 1982, 20, 107-116 C. Heitner-Wirguin, Recent advances in perfluorinated ionomer membranes structure, properties and application, J. Membr. Sci., 1996, 120, 1-33 G. Gebel and J. Lambard, Small-angle scattering study of water-swollen perfluorinated ionomer membranes, Macromolecules,... 

Cation-exchange membranes, perfluorosulfonic acid ionomer, 125... 

The sensitivity to hydrolysis is a key issue in many applications. The ester bond in 4GT-PTMO copolymers is sensitive to hydrolysis however, it is fairly protected since most of the ester is contained in a crystalline structure. The addition of a small amount (1-2%) of a hindered aromatic polycarbodiimide substantially increases the lifetime of this material in the presence of hot water or steam (Brown et al., 1974). Polyurethanes are susceptible to hydrolytic attack, especially those with polyester soft segments. However, polyester soft segment polyurethanes are generally more resistant to oils, organic solvents, and thermal degradation. lonomers will swell when exposed to water in fact, a commercial hydrated perfluorosulfonic ionomer (Nation) is used as a membrane separator in chlor-alkali cells. Styrene-diene copolymers and polyolefin TPEs are insensitive to water. 

M. Saito, S. Ikesaka, J. Kuwano, J. Qiao, S. Tsuzuki, K. Hayamizu, T. Okada, Mechanisms of proton transport in alcohol-penetrated perfluorosulfonated ionomer membranes for fuel cells. Solid State Ionics 178 (2007) 539—545. 

Gebel G (2000) Structural evolution of water swollen perfluorosulfonated ionomers from dry membrane to solution. Polymer 41 5829-5838... 

Okada, T., et al. 1999. The effect of impurity cations on the transport characteristics of perfluorosulfonated ionomer membranes. /. Phys. Chem. B 103 3315-3322. 

Aquivion E87-12S short-side chain perfluorosulfonic acid (SSC-PFSA) membrane with equivalent weight (EW) of 870 g eq and 120 pm thickness produced by Solvay Specialty Polymers was tested in a polymer electrolyte membrane water electrolyser (PEMWE) and compared to a benchmark Nation N115 membrane (EW 1100 g eq ) of similar thickness [27]. Both membranes were tested in conjunction with in-house prepared unsupported Ir02 anode and carbon-supported Pt cathode electrocatalyst. The electrocatalysts consisted of nanosized Ir02 and Pt particles (particle size 2-4 nm). The electrochemical tests showed better water splitting performance for the Aquivion membrane and ionomer-based membrane-electrode assembly (MEA) as compared to Nafion (Fig. 2.21). Lower ohmic drop constraints and smaller polarization resistance were observed for the electrocatalyst-Aquivion ionomer interface indicating a better catalyst-electrolyte interface. A current density of 3.2 A cm for water... 

At present, perfluorosulfonic ionomer (PFSl) is the most widely used membrane material in well-developed PEMFCs because of its excellent chemical and thermal stability, high ionic conductivity, and good mechanical strength. 

The extrusion method is usually used to produce thick membranes. Since membrane resistance is normally proportional to membrane thickness, thinner membranes are desirable for fuel cell applications. To fabricate membranes thinner than about 50 im, solution-cast perfluorosulfonate ionomer offers some advantages compared to the extrusion method. DuPont produces some Nafion membranes, such as NRE211 and NRE212 (25 and 50 pm thickness, respectively) on a commercial scale. The process is described by Curtin et al. (2004), as shown in Figure 4.2. 

Several groups have found that counterions have a great effect on the thermal stability of perfluoro-sulfonated ionomer membranes (Feldheim et al, 1993 Lage et al., 2004a,b Bas et al., 2009). Using TG analysis, Feldheim et al. (1993) found the thermal stability of Nafion perfluorosulfonated ionomer to be... 

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