Sulfonated Polyarylene Sulfone

Compared to the polymer sulfone membrane, which demonstrates that the improved properties of the composite membranes induce an increase in power density, the strategy for carbon nanotube-sulfonated polyarylene sulfone composite membranes discussed here could potentially be extended to other carbon nanotube-polymer composite systems. Recent advances in the chemistry of carbon nanotube functionalization [54], and further understanding of the interaction between the carbon nanotubes and the polymer, may encourage the preparation of a variety of new composite materials. 

Carbon nanotubes are being increasingly used for the reinforcement of plastics, including epoxy resins [57-59], polyamides [55, 60-62], polyimides [63], poly-silsesquioxane [64], polycaprolactam [65], polyethylene oxide [66], polyethylene [67, 55,62], polyurethane [67], ethylene-vinyl acetate [69-73], polyhydroxybutylene-co-hydroxyvalerate [75], ethylene-propylene diene terpolymer [73], and sulfonated polyarylene sulfone [53]. 

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Joo and co-workers [22] have discussed a new type of composite membrane, consisting of functionalised carbon nanotubes (CNT) and sulfonated polyarylene sulfone (sPAS) for direct methanol fuel cell applications. The CNT modified with sulfonic acid or platinum-rubidium (PtRu) nanoparticles were dispersed within the sPAS matrix by a solution casting method to give SOs-CNT-sPAS or PtRu-CNT-sPAS composite membranes, respectively. Characterisation of the composite membranes revealed that the functionalised CNT were homogeneously distributed within the sPAS matrix and the composite membranes contained smaller ion clusters than the neat sPAS. The composite membranes exhibited enhanced mechanical properties in terms of tensile strength, strain and toughness, which leads to improvements in ion conductivity and methanol permeability compared with the neat sPAS membrane, which demonstrates that the improved properties of the composite membranes induce an increase in power density. The strategy for CNT-sulfonated composite membranes in this work can potentially be extended to other CNT-polymer composite systems. 

The crosslinking of a sulfonylated polyarylene ether sulfone was accomplished by addition of CDI and bis-4-aminophenylsulfone as crosslinking agents [23] a) Activation of the sulfonic acid group... 

A substantial intramolecular protective effect by phenyl groups in polymers is shown by the low G values for Hz and crosslinking in polystyrene (substituent phenyl) and in polyarylene sulfones (backbone phenyl), as well as many other aromatic polymers. The relative radiation resistance of different aromatic groups in polymers has not been extensively studied, but appears to be similar, except that biphenyl provides increased protection. Studies on various poly(amino acid)s indicate that the phenol group is particularly radiation resistant. 

Of all the hydrocarbon-based PEMs, this group most likely has the largest variety of different systems. This is probably due to the wealth of prior knowledge of the nonsulfonated analogues that have been developed over the last several decades as well as the general expectation of higher thermal stability, better mechanical properties, and increased oxidative stability over polystyrene-based systems. Within the context of this section, polyarylenes are systems in which an aryl or heteroaryl ring is part of the main chain of the polymer. This section will, therefore, include polymers such as sulfonated poly (ether ether ketone) and sulfonated poly(imides) but will not include systems such as sulfonated polystyrene, which will be covered in Section 3.3.I.3. 

Another class of polyarylene-based PEMs that has been extensively studied, primarily by Hickner et al.,i44 is the sulfonated poly(aryl ether sulfone)s... 

As will be described in Section 3.3.2.1, direct sulfonation also makes it considerably easier to generate sulfonated block copolymer polyarylenes. 

Xing, D. and Kerres, J. 2006. Improved performance of sulfonated polyarylene ethers for proton exchange membrane fuel cells. Polymers for Advanced Technologies 17 591-597. 

The first heterocycle-based systems that had some relevance in the development of new types of fuelcell membranes were sulfonated polyarylenes ° and... 

Ti and Zr containing polytetramethylene oxide (PTMO) ceramic hybrid materials have lately been prepared by a sol-gel technique [61, 62]. Trialkoxy silane capped organic oligomer (PTMO or polyarylene ether sulfones) backbones with titanium isopropoxide or Zr-(n-propoxide) are used in this process ... 

Sulfonation is very useful chemical modification of polymer, as it induces high polarity in the polymer changing its chemical as well as physical properties. Sulfonated polymers are also important precursors for ionomer formation [75]. There are reports of sulfonation of ethylene-propylene diene terpolymer (EPDM) [76, 77], polyarylene-ether-sulfone [78], polyaromatic ether ketone [79], polyether ether ketone (PEEK) [80], styrene-ethylene-butylene-styrene block copolymer, (SEBS) [81]. Poly [bis(3-methyl phenoxy) phosphozene] [82], Sulfonated polymers show a distinct peak at 1176 cm"1 due to stretching vibration of 0=S=0 in the -S03H group. Another peak appears at 881 cm 1 due to stretching vibration of S-OH bond. However, the position of different vibrational bands due to sulfonation depends on the nature of the cations as well as types of solvents [75, 76]. 

Polyarylenes, in particular different types of poly(arylene ether ketone)s, have been the focus of much hydrocarbon membrane research in recent years. - - With good chemical and mechanical stability under PEM fuel cell operating conditions, the wholly aromatic polymers are considered to be the most promising candidates for high-performance PEM fuel cell applications. Many different types of these polymers are readily available and with good process capability. Some of these membranes are commercially available, such as poly(arylene sulfone)s and poly(arylene... 

H. Scheckenbach, A. Schleicher, and J. Kulpe. Mixtures of polyarylene sulfones with polyarylene sulfoxides and polyarylene sulfides. US Patent 5 780 561, assigned to Hoechst Aktiengesellschaft (DE), July 14, 1998. 

U. Eichenauer, E. Neufeld, A. Ludwig, T. Sauer, and A. Ulzhofer. Production of polyarylene-ether-sulfone useful for coating, especially to produce sliding surface. DE Patent 19 816955, assigned to Basf AG (DE), October 21,1999. 

Several non-fluorinated alternative polymers have been proposed for DAFC, mainly based on sulfonated ionomers with an aromatic or aliphatic hydrocarbon skeleton [7], Kim and Pivovar [4] have reported the number of DMFC alternative membranes papers appearing in open hterature for years 1994—2004, showing that polyarylenes, polyvinyl alcohols, grafted and block polystyrenes copolymers, and polyimides were among the most studies polymer electrolytes. In view of the dramatic increase in the number of publications since 2005 (see Fig. 6.1), the trends have changed, as shown in Table 6.1, which sununaiized the publications in open literature for the period 2005-2012, as compared to the previous period. 

Numerous ways to evaluate the degradation behaviour of polyarylene sulfones are reported in the literature. Danilina and co-workers [17] used infrared (IR) analysis for the pyrolysates of PES and PSF along with a change in the absorption peaks after two hours at 470 °C, they showed the formation of sulfur dioxide and phenol from the scission of sulfone and ether linkages. Crossland and co-workers [18] reported the results of TGA and Py-MS in the evaluation of the pyrolysis mechanism and pyrolysates of various PSF main-chain scission and hydrogen abstraction were indicated. However, the relative stability of the different PSF could not be postulated... 

Reactive flexibilizers such as polysulfldes, urethanes, polybutadienes, and polyesters are copolymerized with epoxies to increase flexibihty, improve adhesion, modify electrical properties, and improve resistance to chemicals. Nonreactive extenders such as thermoplastics, asphaltums, and waxes are used to modify properties and reduce the cost of the compounds. Polyarylene ether sulfone as an extender in epoxy resins increases the fracture toughness fivefold with only a slight drop in Tg. 

R. Viswanathan, "Synthesis and Characteristics of Polyarylene Ether Sulfones", Ph.D. Dissertation, Virginia Polytechnic Institute and State University, 1981 manuscripts in preparation. 

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