Membranes sulfonate base

Numerous y-secretase inhibitors featuring sulfonamide- and sulfone-based scaffolds have been disclosed. Bicyclononane thiophene sulfonamide 40 reduced brain Ap in transgenic mice by 50% after a dose of 100 mg/kg [100]. High potency (A p IC50 = 0.5 nM) and improved oral activity (ID50 = 17 mg/kg) was found in a series of related sulfamides represented by 41 [101]. Tetrahydroquinoline (42) and piperidine (43-44) sulfonamides have been developed [102-104]. Elaboration of the piperidine series with the cyclopropyl substituent present in 44 improved in vitro potency (Aft IC50 = 2.1 nM in membrane assay) and in vivo activity in transgenic mice (plasma Ap = 2% of control after oral dose of 30 mg/kg). Reductions of A p in the cortex were reported to be comparable to those observed in plasma. 

One of the earliest proton exchange membranes was based on sulfonated polystyrene where divinylbenzene was used as a cross-linking unit for extra stability. Developed by General Electric, this membrane (21) was cheap and easy to manufacture, and it was used for fuel cells in the Gemini space pro-gram.i However, due to the sensitivity of the benzylic hydrogen to radical attack, lifetimes for these membranes under FC operating conditions were quite low. Thus, little work has been carried out on these systems since their inception. 

Figure 18 shows the temperature dependence of the proton conductivity of Nafion and one variety of a sulfonated poly(arylene ether ketone) (unpublished data from the laboratory of one of the authors). The transport properties of the two materials are typical for these classes of membrane materials, based on perfluorinated and hydrocarbon polymers. This is clear from a compilation of Do, Ch 20, and q data for a variety of membrane materials, including Dow membranes of different equivalent weights, Nafion/Si02 composites ° ° (including unpublished data from the laboratory of one of the authors), cross-linked poly ary lenes, and sulfonated poly-(phenoxyphosphazenes) (Figure 19). The data points all center around the curves for Nafion and S—PEK, indicating essentially universal transport behavior for the two classes of membrane materials (only for S—POP are the transport coefficients somewhat lower, suggesting a more reduced percolation in this particular material). This correlation is also true for the electro-osmotic drag coefficients 7 20 and Amcoh...

The important acid activity in Nafion is appropriately represented by trifluo-romethane sulfonic (triflic) acid, CF3SO3H see Fig. 1.5. Dielectric spectroscopy has suggested that a significant amount of triflic acid is not dissociated in the ionic melt at 50% mole fraction of water (Barthel et al, 1998). But the deprotonation chemistry of hydrated triflic acid hasn t been experimentally studied over the wide range of hydration and temperature that would be relevant to the function of sulfonate-based polyelectrolyte membrane materials. 

Furthermore, in 2001, Ballard entered an alliance with Victrex to produce two new membrane alternatives. One membrane is based on sulfonated poly(arylether) ketone (a variant of PEEK) supplied by Victrex, which may be better suited to PEMFC fabrication applications. In March 2002, U.S. Patent 6,359,019 was issued to Ballard Power for a graft-polymeric membrane in which one or more trifluorovinylaromatic monomers are radiation graft polymerized to a preformed polymeric base. The strucmres of BAM membranes have been studied by way of small-angle neutron scattering (SANS) [97]. The study of the ionomer peak position suggests the existence of relatively small ionic domains compared to Nalion, despite large water content. Phase separation in the polymer matrix is possibly crucial for the membrane s mechanical and transport properties. 

The most diffused material for membranes is based on co-polymers of tetrafluoroethylene (TEE) with perfluorosulfonate monomers. The resulting co-polymer is constituted by polytetrafluoroethylene polymeric chain (PTFE, commercially known as Teflon) in which some fluorine atoms are substituted by sulfonated side chains. The monomer perfluoro-sulfonyfluoride ethyl-propyl-vinyl ether is used in membranes commercialized by Dupont with the registered trademark Nafion (Fig. 3.2), which is the most well-known material used as electrolyte in PEM fuel cells. 

Special Property Membranes. In the literature, there are numerous methods reported for the preparation of ion-exchange membranes with special properties,87-89 for instance, for use as battery separators, ion-selective electrodes, or in the chlor-alkali process. Especially membranes recently developed for the chlor-alkali industry are of commercial significance. These membranes are based on polytetrafluoroethylene and carry sulfone groups in the bulk of the membrane phase and carboxyl-groups on the surface as the charged moiety. They combine good chemical stability with high selectivity and low electric resistance. 

These membranes are based on perfluorinated polymers that will withstand oxidatWe conditions and high temperatures that would be destructive to hydrociubon-based membranes. Sulfonic or caiboxylic acid groups, or both, are affixed chemically to the perfluorinated polymers to impart cation-exchange characteristics. 

C. Liang, H. Hisatani, T. Maruyama, Y. Ohmukai, T. Sotani, H. Matsuyama, Influence of chemical compositions on the properties of random and multiblock sulfonated poly(arylene ether sulfone)-based proton-exchange membranes, J. Appl. Polym. Sci. 116 (1)(2010) 267-279. 

To improve hydrolytic-oxidative stability and maintain other desirable properties, Zhang et al. also developed novel fluorinated SPI membrane materials based on 4,4 -binaphthyl-l,T,8,8 -tetracarboxylic dianhydride (BTDA) and wholly aromatic diamine, 2,2 -fcw(3-sulfobenzoyl) benzidine (2,2 -BSBB) [249], To obtain SPI copolymers (Scheme 3.30) with a controlled degree of sulfonation (DS), they used two types of non-sulfonated diamine monomers, with or without fluorinated groups, and analyzed their properties. All of the BTDA-based co-SPI membranes exhibited excellent hydrolytic-oxidative stability and... 

Solubility of the three commercial polysulfones follows the order PSF > PES > PPSF. At room temperature, all three of these polysulfones as well as the vast majority of other aromatic sulfone-based polymers can be readily dissolved in a handful of highly polar solvents to form stable solutions. These powerful solvents include NMP, DMAc, pyridine, and aniline. 1,1,2-Trichloroethane and 1,1,2,2-tetrachloroethane are also suitable solvents but are less desirable because of their potentially harmful health effects. In addition to being soluble in the aforementioned list, PSF is also readily soluble in a host of less polar solvents by virtue of its lower solubility parameter. These solvents include tetrahydrofuran (THF), 1,4 dioxane, chloroform, dichloromethane, and chlorobenzene. The relatively broad solubility characteristics of PSF have been key in the development of solution-based hollow-fiber spinning processes in the manufacture of polysulfone asymmetric membranes (see Membrane Technology). The solvent list for PES and PPSF is short because of the propensity of these polymers to undergo solvent-induced crystallization in many solvents. When the PES structure contains a small proportion of a second bisphenol comonomer, as in the case of RADEL A (British Petroleum) polyethersulfone, solution stability is much improved over that of PES homopolymer. 

Boaventura et al. [12] reported the generation of polytriazole based proton conducting membranes. Sulfonated polytriazole membranes were doped with three different agents IH-benzimidazole-2-sulfonic acid, benzimidazole and phosphoric acid. Figure 1.13 also shows the storage modulus and tan 6 curves for pure polymer... 

Several materials have been studied on the goal of producing cost-effective PFMs [55-62]. Some of these are PBI-based membranes, polysterene membranes, sulfonated polyimide, cross-Unked poly(vinyl alcohol), and phosphobenzene, sulfonated poly(aryl ether ketone) —based manbranes. Sulfonation of aromatic thermoplastics such as polyether sulfone, polybenzimidazole, polyimides, and poly(ether ether ketone) makes them proton conductive suitable for fuel cell... 

A current industrial application of ionomers is their use as permselective membranes for the chloralkali process. The ionomers used in these membranes are based on a poly(tetrafluoroethylene) backbone containing occasional ether linkages with ionic side groups. These are based upon either sulfonate or carboxylate salts. 

Suda et al. [288] reported the synthesis and characterization of a series of sulfonated star-hb polyimides (S-hb-Pls) without any crosslinking for use as proton exchange membranes. Sulfonated anhydride-terminated polyimides with different molecular weights (M v = 59,000, 200,000 and 300,000 Da) based on monomer combination 1,4,5,8-naphthalene tetracarboxylic dianhydride/4,4 -diaminobiphenyl 2,2 -disulfonic acid (NTDA/BDSA) were synthesized using different molar ratios of BDSA NTDA. The amine-terminated hb-Pl based on monomer combination 4,4-(hexafluoroisopropylidene)diphthalic anhydride/tris(4-aminophenyl)amine (6EDA/TAPA) was also prepared. Scheme 33 shows the monomer combinations used for the preparation of (S-hb-Pl). 

They also published their works on novel cardo poly(aryl ether sulfone)-based AEMs containing pendant quaternary ammonium groups on aliphatic side chains by direct polymerization using functionalized monomer (Figure 11.14b). TEM observation revealed that the obtained membranes exhibited a distinct phase-separated morphology comprised interconnect ionic clusters in the size of 1-2 nm. The resulting membranes with lEC of 1.44 mmol/g displayed ionic conductivities varied from 30 to 41 mS/cm at 20°C-60°C. 

Neither the top nor the bottom sides of the membranes showed any regular dependence of chemical composition on the degree of sulfonation. Based on the ESCA analyses, the degree of sulfonation at the membrane surface does not reflect the bulk... 

This article focuses on the commercial, ethylene-based ionomers and includes information on industrial uses and manufacture. The fluorinated polymers used as membranes are frequently included in ionomer reviews. Owing to the high concentration of polar groups, these polymers are generally not melt processible and are specially designed for specific membrane uses (see Fluorine compounds, organic—perfluoroalkane sulfonic acids Membrane technology). 

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