Sulfonation of PEEK

Fig. 6 Degree of sulfonation of PEEK (a) and PPBP (b) as a function of reaction time at room temperature [7,35]...

Sulfonation of PEEK in concentrated sulfuric add at room temperature is accompanied by incorporation of not more than one sidfoiuc add group into each repeating unit of the polymer [86,90,93,94]. FT-IR spectroscopy studies show that PEEK is sulfonated at the phenylene ring between the ether... 

The sulfonation of PEEK (46) in concentrated sulfiiric acid or in its mixture with methanesnlfonic acid [75-72-2] gives pol5nneric material which is soluble in organic solvents, eg, DMF (138), and good membranes with interesting properties were obtained by processing from these solntions (139-142). 

Sulfonation of PEEK (19.2 wt%) resulted in misdbihty with PA6, as observed from Tg and FTIR characterization [479]. The Zn + salt showed a higher level of interaction than the Li+ salt, which in turn showed improved interaction with PA6 over the free acid. Hydrogen bonding was ascribed to the specific interaction of the free acid and PA6. For the salts, ion-dipole interaction was ascribed to a complex of Li+ with the amide carbonyl and Zn with the amide nitrogen. 

Fig. 3 Degree of sulfonation of PEEK in dependence of time. Sulfonation by concentrated sulphuric acid at room temperature (curve taken from [1])...

Polyetheretherketone (PEEK) fibers electrical properties of, 23 718 properties of, 20 199t sulfonation of, 23 717 PEEK-based composites, 26 764 Peel-apart color films, 19 286 Peel-apart film(s), 19 274, 281, 282, 299, 314... 

Kobayashi et al. reported sulfonation of poly(4-phenoxybenzoyl-1,4-phenylene) (PPBP) with sulfuric acid and compared the data with those of sulfonated PEEK. As reported, the authors employed sulfuric acid for the sulfonation reaction to avoid or at least minimize degradation of the polymer by chlorosulfonic acid or fuming sulfuric acid (Figure 27). 

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]. 

Furthermore, in 2001, Ballard entered an alliance with Victrex to produce two new membrane alternatives. One membrane is based on sulfonated poly(arylether) ketone (a variant of PEEK) supplied by Victrex, which may be better suited to PEMFC fabrication applications. In March 2002, U.S. Patent 6,359,019 was issued to Ballard Power for a graft-polymeric membrane in which one or more trifluorovinylaromatic monomers are radiation graft polymerized to a preformed polymeric base. The strucmres of BAM membranes have been studied by way of small-angle neutron scattering (SANS) [97]. The study of the ionomer peak position suggests the existence of relatively small ionic domains compared to Nalion, despite large water content. Phase separation in the polymer matrix is possibly crucial for the membrane s mechanical and transport properties. 

Fig. 7 Chemical structures of some sulfonated polymers and a polyimide (A) sulfonated polyetheretherketone, PEEK, PSE (B) sulfonated polyphenylenesulfide, PPS (C) sulfonated polysulfone (D) poly(4,4 -biphenol) (4,4 -dichlorodiphenyl sulfone), BPSH-XX (XX is mol% of disulfdonated units) (E) sulfonated polybenzimidazole, PBI (F) polyimide.

N. Shibuya and R.S. Porter, Kinetics of PEEK sulfonation in concentrated sulfuric acid, Macromolecules, 1992, 25, 6495-6499 F. Wang and J. Rovers, Functionalization of poly(aryl ether ether ketone) (PEEK) Synthesis and properties of aldehyde and carboxylic acid substituted PEEK, Macromolecules, 1993, 26, 5295-5302. 

Porous PEEK membranes are obtained from solutions in concentrated sulfuric acid. In this process, PEEK can undergo sulfonation in the concentrated sulfuric acid media and looses some of its desirable sought after properties. It has been suggested to get non-sulfonated porous PEEK membranes from less concentrated sulfuric acid to prevent sulfonation. The membranes are formed by casting a PEEK solution to form a film followed by coagulation." This process produces large amounts of waste acid. 

The proton conductivity of sulfonated poly(ether ether ketone) can be improved by using special types of PEEK, namely, block copolymers consisting of a hydrophobic and a hydrophilic block. 

Sulfonated PEEK-WC membranes with a degree of sulfonation of 15-40%, have been tested as dense membranes for fuel cell applications. A solvent evaporation technique, with dimethylacetamide as the solvent was used to prepare dense membranes. A water uptake of up to 15% bas been found for the dense membranes at 80°C. The membranes exhibit electrochemical performances comparable to Nation membranes. ... 

L. Paturzo, A. Basile, A. lulianelh, J. C. Jansen, I. Gatto, and E. Passalacqua. High temperature proton exchange membrane fuel cell using a sulfonated membrane obtained via H2SO4 heatment of PEEK-WC. Catal. Today, 104 (2-4) 213-218, June 2005. 

In blends of PPESK and sulfonated poly (ether ether ketone) (PEEK), both methanol permeability and proton conductivity increase nonlinearly with increasing content of PEEK. Sulfonated PAES copolymers obtained from sulfonated 4,4 -dichlorodiphenyl sulfone, 4,4 -dichlorodiphenyl sulf-one and phenolphthalein have been tested with respect to their use for direct methanol fuel cell application. The proton conductivity increases linearly with the degree of sulfonation, but the methanol permeability increases linearly up to 20 mol-% sulfonated monomer content. Above this level, a sudden increase in permeability is observed. This effect is referred to as percolation threshold. 

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. 

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-... 

The development of polyaryls, in particular polyetherketones (PEEK), as a substitute of perfluorinated polymers was mainly based on cost and stability considerations [1]. Sulfonated polyetherketones has been found to be durable under fuel cell operation conditions over several thousand hours [185]. Victrex Company is the main producer of PEEK polymer and its sulfonation can be performed directly on the polymer backbone or by polymerization of sulfonated monomers [7]. Hoechst-Aventis and Eumatech commercialize sulfonated PEEK (sPEEK) and sulfonated poly(phtalazinone ether ketone) (sPPEK) membranes for fuel cell applications [3]. 

The sulfonation degree of PEEK membranes reported in the literature range from 10 % to 98 %, and the corresponding ion-exchange capacity (lEC) varies between 1 to more than 2.5 meq.g [185], and the proton conductivity is strongly... 

Side-chain-type sulfonated hydroxynaphthalene PEEK with hydroxyl groups was synthesized by a post-grafting method. The degree of sulfonation of the polymers could be well controlled. 

Sulfonated hyperbranched PEEK was synthesized by the sulfonation of fluoro-terminated hyperbranched poly(aryl ether ketone) [86], These materials were used in combination with sulfonated linear PEEK for proton exchange membranes. 

X. Feng, Sulfonation of poly(ether ether ketone) (PEEK) kinetic study and characterization, J. Appl. Polym. Sci. 82 (11) (2001) 2651-2660. 

Among other studies, the sulfonation of a new PEEK based polymer, the polyetheretherketone/cardo-group (PEEK-WC), represents at moment a way to obtain a new sulfonated polymer (S-PEEK-WC) showing interesting electrochemical performances and very good thermo-chemical properties with respect to the Nafion. 

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