ACPs, sulfonated

Some special reaction with a particularly designed route can be used to synthesize azo BCs. For instance, a series of poly(vinyl ether)-based azo LCBCs were synthesized by using living cationic polymerization and free-radical polymerization techniques (Serhatli and Serhatli, 1998). As shown in Scheme 12.8, 4.4 -azobis(4-cyano pentanol) (ACP) was used to couple quantitatively two well-defined polymers of LC living poly(vinyl ether), initiated by the methyl trifluor-omethane sulfonate/tetrahydrothiophene system. Then the ACP in the main chain was thermally decomposed to produce polymeric radical, which was used to initiate the polymerization of MMA or styrene to obtain PMMA-based or PS-based azo BCs (AB or ABA types). 

Aromatic polymers containing sulfonic acid groups can be prepared by sul-fonation of high molecular mass ACPs or by condensation of monomers containing sulfonic acid groups. 

The simplest and the most widely-used method for the synthesis of sulfonated ACPs involves sulfonation of different classes of polymers, such as substituted poly-(l,4-phenylenes) [34,35], poly-(p-xylylene [36,37]), poly-(l,4-oxyphenylenes) [38-44], poly(ether ether ketones) (PEEK) [46- 59], polyary-lenefether sulfones) [3,60-74], poly(phenylene sulfides) [75], polyphenyl-quinoxalines [76-79], polybenzimidazoles [80], polyperyleneimides [81] and some other ACPs. 

The chemical structures of sulfonated poly(4-phenoxybenzoyl-l,4-phenyl-ene) (S-PPBP) (1), poly(p-xylylene) (S-PPX) (2), poly(phenylene sulfide) (S-PPS) (3), poly(phenylene oxide) (S-PPO) (4), poly(ether ether ketone) (S-PEEK) (5), poly(ether ether sulfone) (S-PEES) (6), arylsulfonated poly(ben-zimidazole) (S-PBl) (7) sulfonated polyphenylquinoxiiline (S-PPQ) (8) and sulfonated phenoxy polyperyleneimide (PSPPI) (9) are shown below. ACPs are sulfonated using common sulfonating agents [82-85]. In particular, PEEK can be sulfonated in concentrated sulfuric acid [50], chlorosulfonic acid [86], SO3 (either pure or as a mixture) [53,65,86,87], a mixture of methanesulfonic acid with concentrated sulfuric acid [88] and acetyl sulfate [89,90]. 

Sulfonation of ACPs was systematically studied taking a number of polymers (first of all, PEEK and PPBP) as examples [7]. It was shown that sulfonation with chlorosulfonic or fuming sulfuric acid is sometimes accom-... 

Sulfonated ACPs are prepared both by direct sulfonation and by polycondensation and polycyclocondensation of sulfonated compounds. Synthesis of the first sulfonated poly(p-phenylene) was reported by Wegner and co-workers [103]. The Suzuki coupling of diboronic ethers with dibromo-aromatic monomers furnished poly(p-phenylene) with 95% yield. 

Using this approach, one can not only prepare polymers with regular arrangement of sulfonic acid groups, but, sometimes, introduce a large number of sulfonic acid groups into the AGP macromolecules compared to the sulfonation of ACPs. 

The most important properties of sulfonated ACPs are their thermal sta-bihty, water uptake and proton conductivity. PEMFCs and electrochemical... 

Proton-conducting polymer electrolyte membranes based on ACPs such as S-PPBP and sulfonated poly(phenylene sulfide) contain rather large amoimts of bound water. This seems to be the reason for such a sahent featme of these membranes as an increased proton conductivity at high temperatmes and/or low humidities. This conclusion was confirmed by the results of differential scanning calorimetry (DSC) studies of these systems [7]. 

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