PEEKK, sulfonated

Figure 17. Room-temperature proton conductivity of two Dow membranes of different EW values, Nation, two varieties of sulfonated poly (ary lene ether ketone) s (S— PEK and S—PEEKK, unpublished data from the laboratory of one of the authors), and sulfonated poly(phenoxyphos-phazene)s (S—POPs °9 of different equivalent weights (685 and 833 g/equiv), as a function of the degree of hydration n = [H20]/I—SO3H] (number below the compound acronym/ name indicates the EW value).

Figure 12.10. Computed and experimentally determined proton self-diffusion coefficients in Nafion 117 and 65% sulfonated PEEKK membranes plotted as a function of water content expressed as the number of water molecules per sulfonic add group. The comparison to the experimental measurements indicates the generally remarkable agreement (within 15%) range of membrane hydration. Taken from Ref. [23].

FIGURE 5.3 Schematic of the two zones in hydrated Nafion and sulfonated poly(ether ether ketone ketone) (PEEKK). This scheme illustrates the distinctions in the hydrophihc/hydrophobic separation, the connectivity of the water and ion domains, and the separation of the -SOJ groups [19]. (For color version of this figure, the reader is referred to the onUne version of this book.)... 

FIGURE 5.4 Computed and experimentally determined proton self-diffusion coefficients in Nafion 117% and 65% sulfonated PEEKK membranes as a function of water content [20]. 

Fig. 17.3 Stimulated view of the microstructures of Nafion, and alternative polymeric material, sulfonated PEEKK. (Reprinted with permission from [28]. Copyright 2001 Elsevier)...

Poly(ether ether) ketone (PEEK) and poly(ether ether ketone ketone) (PEEKK) are highly stable polymers with good potential for application in DMFCs [10,17,18]. They are semicrystalline and display excellent chemical and thermal stability. They may be sulfonated through direct polymerization of sulfonated monomers or by postsulfonation, the latter again leading to materials with less tightly controlled degree and location of sulfonation, but with the attraction that it is a simple and low-cost approach [19]. 

Nafion 117 in Hquid water takes up more water per sulfonic acid group than S-PEEKK of lEC values between 0.78mmol/g and 1.78mmol/g up to a certain temperature, which depends on the lEC value of the S-PEEKK. At this temperature, which is 65 °C for lEC = 1.78mmol/g, 80 °C for lEC = 1.4 mmol/g, 100 °C for lEC = 0.78 mmol/g, the water content of the S-PEEKK membranes increases tremendously. Nafion shows similar behavior only at a temperature of 140 °C. Until this temperature is reached, its molar water content is almost constant at A. = 20. The excess swelling of S-PEEKK at temperatures of 100 °C or less causes severe problems in using these materials as membranes in fuel cells. 

Stability and performance of AEM prepared using poly(4-vinyl pyridine-costyrene), quaternized with 1-bromooctane, and deposited on fibrous woven paper was unsatisfactory [189]. Sanchez and coauthors [190] discussed problems related to the use of certain AEMs. They pointed out that the so-called Hoffman degradation that involves attack of a hydroxyl on a-hydrogen in p-position to a quaternary ammonium attached to an aliphatic chain may cause its removal, followed by release of a tertiary amine and formation of a double bond at the end of a broken chain. Attachment of DABCO on short leash prevented chain break due to Hoffman degradation, but release of DABCO and generation of a double bond attached to the chain could take place. Perhaps thermal cross-linking by DABCO of poly(vinyl benzyl chloride) may solve this problem. Sulfonated polymers prepared by polymerization or copolymerization of phosphazene, siloxans, styrene, vinylidene fluoride, and various monomers with aromatic backbones, and possibly with aliphatic spacers, have been used. Various imides as well as PPS, PEK, PEEK, PSU, PEEKK, and PPSU can also be used [190,191]. 

Victrex Company is the main producer of the PEEK polymer in the market now and its sulfonation is generally performed via sulfonic acid groups (SO3H), which are directly introduced onto the polymer backbones, by modification or by polymerization of sulfonated monomers. Sulfonated PEK, PEEK, PEEKK, and PEEK-WC show interesting behaviors in terms of wettability, water flux, antifouling capacity, low fuel... 

PEEKK sample, which suggests the successful introduction of sulfonic acid groups in SPEEKK. 

Typical blend polymers for PBI include poly (aryl ether ketone) (PARK), pofyetherimide (PEI), poly (aryl ether sulfone), poly (phenylene sulfide), and mixtures thereof. Different types of PAEK resins (Fig. 7.5) include PEK, PEEK, PEKEKK, PEKK, PEEKK, etc., several of which have melting points over 300°C. PAEK resins with relatively low Tg values can be further improved by the addition of reinforcement fillers, such as fiberglass, carbon fibers, and ceramic or mineral fillers. Such additions, however, can... 

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