Poly arylene Ether Ketone s

PEEK e.g. Victrex PEEK (Victrex), Gatone PEEK (Gharda), Kadel (Solvay), CoorsTek PEEK (CoorsTek), Ketron (Quadrant) 

All commercially available poly(arylene ether ketone)s follow the same scheme of composition as those shown above. They are semicrystalline, and since the only difference between these structures is the sequence of ether 

Presently, however, only three types of poly(arylether ketone)s are still produced commercially PEEK, PEK, and PEKK. Most work for proton conducting membranes has been done based on PEEK, but the others have been used as well (1,6,7,13-32]. 

Water uptake was studied by Kreuer [7,31] and compared to Nafion . For an interpretation of these data, one needs to consider that the sulfonic acids involved are strong acids, which will dissociate when possible. This requires a certain amount of water, depending on the degree to which the ions after 

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. 

Poly(arylene ether ketone)s have the following general structure  

Depending on the number of ether and keto groups in the constitutional repeating units one distinguishes between poly(ether ketone)s (PEK, x = y = 1), poly (ether ether ketone)s (PEEK, x = 2, y = 1), poly(ether ketone ketone)s (PEKK, X = 1, y = 2), and poly(ether ether ketone ketone)s (PEEKK, x = y = 2). 

In analogy to poly(arylene ether sulfone)s, there are two different polycondensation methods for the technical synthesis of poly(arylene ether ketone)s  

Depending on the type of the monomers, a large number of crystaUizable poly (arylene ether ketone)s with different contents of keto and ether groups can be synthesized by employing one of the two procedures. The ratio of keto to ether groups determines essentially the thermal properties of the linear unsubstituted poly 

In addition to the excellent thermostability, which is due to their high crystallite melting points, poly(arylene ether ketone)s exhibit a very good chemical resistance because of their low solubility. 

They display a high non-flammability, and for a partly crystalline material, an unusually high impact strength. The high stability of the melt permits one to process the material using conventional methods (injection molding, extrusion). Accordingly, poly(arylene ether ketone)s are used in the automobile, electrical, and electronic industry. 

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The general approaches for the synthesis of poly(arylene ether)s include electrophilic aromatic substitution, nucleophilic aromatic substitution, and metal-catalyzed coupling reactions. Poly(arylene ether sulfone)s and poly(arylene ether ketone)s have quite similar structures and properties, and the synthesis approaches are quite similar in many respects. However, most of the poly(arylene ether sul-fone)s are amorphous while some of the poly(arylene ether)s are semicrystalline, which requires different reaction conditions and approaches to the synthesis of these two polymer families in many cases. In the following sections, the methods for the synthesis of these two families will be reviewed. 

Similar to the synthesis of polysulfones, poly(arylene ether ketone)s can also be prepared by using either AA and BB monomers or an AB monomer. 

The nucleophilic aromatic substitution reaction for the synthesis of poly(arylene ether ketone)s is similar to that of polysulfone, involving aromatic dihalides and aromatic diphenolates. Since carbonyl is a weaker electron-withdrawing group titan sulfonyl, in most cases, difluorides need to be used to afford high-molecular-weight polymers. Typically potassium carbonate is used as a base to avoid the... 

The Suzuki reaction was also used to prepare the polyketone since this particular reaction tolerates the subsequent step (Scheme 6.19).135 Palladium-catalyzed cross-coupling of aromatic diacid chlorides and bis(trimethylstannane) monomers was utilized to prepare poly(arylene ether ketone)s.136... 

Miller et al. were the first to report the synthesis of hyperbranched poly(arylene ether ketone)s.157 They used 3,5-bis(4-fluorobenzoyl)phenol as the starting material, as shown in Scheme 6.20. 

Poly(arylene ether ketone)s can also be modified by introducing the functional groups using similar approaches to polysulfones. For example, poly(arylene ether ketone)s were sulfonated.189 In addition, o-dibenzoylbenzene moieties in the poly(arylene ether)s can be transformed to heterocycles by cyclization with small molecules. These polymers can react with hydrazine monohydrate in the presence of a mild acid in chlorobenzene or with benzylamine in a basic medium.190 Another example of the use of the o-benzyl cyclization strategy is the intramolecular ring closure of poly(arylene ketone)s containing 2,2/-dibenzoylbiphenyl units to form poly(arylene ether phenanthrenes).191... 

Sulfonated hydroquinone was used to prepare functional poly(arylene ether ketone)s, which may be used a gas separation membranes.202... 

PEKEKK. See Poly(arylene ether ketone ether ketone ketone) (PEKEKK) PEKK copolymer, alternating, 334 PEKs. See Poly(arylene ether ketone)s (PEKs)... 

As described earlier, the choice of bisphenols for the polymerization of poly(arylene ether ketone)s is large. In particular, the electrochemical properties of the above monomer copolymerized with bisphenol AF were studied. The fundamental PEM characteristics (water uptake and conductivity) were analogous to those of the BPSH systems for a given lEC. 

Figure 13. A few microstructural parameters for Nafion and sulfonated poly(arylene ether ketone)s,i as a function of the solvent (water and/or methanol) volume fraction Xy. (a) the internal hydrophobic/hydrophilic interface, and (b) the average hydrophobic/hydrophilic separation and the diameter of the solvated hydrophilic channels (pores).

Figure 14. Solvent (water, methanol) diffusion coefficients of (a) Nafion 117 (EW =1100 g/equiv) and (b) sulfonated poly(arylene ether ketone)s, as a function of the solvent volume fraction. Self-diffusion data (AiaO. T eOi-i) are taken from refs 197, 224, 226, 255—263 and unpublished data from the laboratory of one of the authors) chemical diffusion coefficients (Z>h2o) are calculated from self-diffu-sion coefficients (see text), and permeation diffusion coefficients are determined from permeation coefficients. ...

Crystalline polymers exhibit the following basic properties They are opaque as long as the size of the crystallites or spherulites, respectively, lies above the wavelength of light. Their solubility is restricted to few organic solvents at elevated temperature. The following crystalline polymers have attained technical importance as thermoplastic materials polyethylene, polypropylene, aliphatic polyamides, aliphatic/aromatic polyamides, aliphatic/aromatic polyesters, poly-oxymethylene, polytetrafluoroethylene, poly(phenylene sulfide), poly(arylene ether ketone)s. 

Due to the side chains this poiymer is amorphous with a glass transition temperature of 185 °C. In contrast, unsubstituted poly(arylene ether ketone)s are crystalline and high melting (T > 300 °C).The iR spectrum shows absorption bands at 3300 cm" and 1710-1730 cm" for the acid group in the side chain and at 1650 cm" for the keto group. 

A new series of functionalized poly(arylene ether ketone)s and their use as modifiers for bismaleimide resins has recently been published (96). In contrast with the former work in this area, the functional groups are not terminal but randomly distributed along the backbone of the poly(arylene ether ketone). The synthesis involves the reaction of 4,4 -difluorobenzophenone and the potassium bisphenates of bisphenol-A and 2,2 -bis(3-allyl-4-hydroxyphenyl) hexafluoro-isopropane or mixtures thereof in DMAc at 155 °C as outlined in Fig. 31. The concentration of the o,o -diallylbisphenol employed in the synthesis determines the concentration of functional propenyl groups. 

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... 

Y. Sakaguchi, A. Kaji, K. Kitamura, S. Takase, K. Omote, Y. Asako, K. Kimura, Polymer electrolyte membranes derived from novel fluorine-containing poly(arylene ether ketone)s by controlled post-sulfonation.Po/ymer2012,53(20), 4388-4398. 

The latest trends in high-performance polymeric materials is towards the development of poly(arylene ether)s and poly(arylene ether ketone)s. They can be used as structural resins because in composite fabrications they offer an attractive combination of chemical, mechanical, and physical properties. 

S.K. Park, S.Y. Kim, Synthesis of poly(arylene ether ketone)s containing trifluoromethyl groups via nitro displacement reaction. Macromolecules 31 (10)(1998) 3385-3387. 

M.H. Jeong, K.S. Lee, Y.T. Hong, J.S. Lee, Selective and quantitative sulfonation of poly(arylene ether ketone)s containing pendant phenyl rings by chlorosulfonic acid, J. Memb. Sci. 314 (1-2) (2008) 212-220. 

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