Poly arylene ethers

A large variety of newer poly(ether imide)s has been described. Included among these are perfluorinated polymers (96), poly(ester ether imide)s (97), poly(ether imide)s derived from A/,Ar-diamino-l,4,5,8-naphthalenetetracarboxyHcbisimide (98), and poly(arylene ether imide ketone)s (99). In addition, many other heterocyHc groups have been introduced into polyether systems, eg, poly(pyrazole ether)s (100) and poly(aryl ether phenylquinoxaLine)s (101) poly(aryl ether oxazole)s with trifluoromethyl groups (102) and polyethers with other heterolinkages, eg, poly(arylether azine)s (103). 

Other organic—inorganic hybrids include poly(ethyloxazoline)—siUca, poly(vinyl alcohol)—siUca, poly(arylene ether) ketone—siUca, polyimide—siUca, polyozoline—sihca, poly(ethylene oxide)—siUca, and polymers—modified alkoxysilane. 

Polymerization Solvent. Sulfolane can be used alone or in combination with a cosolvent as a polymerization solvent for polyureas, polysulfones, polysUoxanes, polyether polyols, polybenzimidazoles, polyphenylene ethers, poly(l,4-benzamide) (poly(imino-l,4-phenylenecarbonyl)), sUylated poly(amides), poly(arylene ether ketones), polythioamides, and poly(vinylnaphthalene/fumaronitrile) initiated by laser (134—144). Advantages of using sulfolane as a polymerization solvent include increased polymerization rate, ease of polymer purification, better solubilizing characteristics, and improved thermal stabUity. The increased polymerization rate has been attributed not only to an increase in the reaction temperature because of the higher boiling point of sulfolane, but also to a decrease in the activation energy of polymerization as a result of the contribution from the sulfonic group of the solvent. 

These thiohydroxamic esters have seen use in grafting of PAN onto PE,iM of PS, PAM and I MPAM onto cellulose127128 and of PS, PMMA, PVP and PAM onto poly(arylene ether sulfone).12 7 The process involves derivitization of a parent carboxy functional polymer to form the thiohydoxamic ester 82 (R=polvmcr) which then behaves as a polymeric transfer agent and/or radical generator. 

Poly(arylene ether ketone) and poly(arylene ether sulfone) were also tried to be incorporated into the hybrids with silica gel by means of the sol-gel procedure [19, 20], For example, triethoxysilyl-terminated organic polymer was subjected to co-hydrolysis with tetraethoxysilane. A systematic change in mechanical and physical properties of the hybrid glass has been found with the content of organic polymer and the annealing temperatures. 

A generalized structure of the poly(arylene ether)s can be represented as in Scheme 6.2. 

Robeson et al. studied the secondary loss transitions of a series of poly(arylene ether)s using a torsion pendulum.15 They found that the secondary loss transitions are closely related to the segmental motion of the aryl ether bonds. The secondary... 

Scheme 6.1 Examples of commercial poly(arylene ether)s.

Scheme 6.2 Generic representation of poly(arylene ether) backbone structure.

GENERAL APPROACHES FOR THE SYNTHESIS OF POLY(ARYLENE ETHER)S 329... 

A wide variety of high-performance polymeric materials have been synthesized by incorporating thermally stable moieties such as sulfone, ketone, or aryl or alkyl phosphine oxide in addition to the ether linkage in poly(arylene ether)s. 

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. 

Poly(arylene ether sulfone)s can be synthesized by two different polysulfonyla-tion reaction routes condensation of AA and BB monomers or self-condensation of AB monomer.26,27 Scheme 6.5 shows two approaches. 

Sulfonic acid catalysts can also be used to prepare poly(arylene ether sulfone)s, such as (CF3C0)20, polyphosphoric acid (PPA),26 MeS03H-P205 mixture,33 and CF3SO3H.34... 

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. 

Scheme 6.9 Synthesis of poly(arylene ether ether ketone) (PEEK) and poly(ether ether ketone ether ketone (PEEKEK) in triflic acid.

Scheme 6.12 Proposed mechanism for the synthesis of poly(arylene ether sulfone) via the potassium carbonate process.8...

Scheme 6.13 Synthesis of poly(arylene ether sulfone)s via silyl ether displacement.

Poly(arylene ether ketone) Synthesis 6.2.2.4.1 Common One-Step Process... 

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... 

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