Aromatic polymers ketones

To date, much effort has been undertaken to develop new alternatives. For example, sulfonated aromatic polymers, i.e., polymers with the sulfonic acid groups directly attached to the main chain or carrying short pendant side chains with terminal sulfonic acid units, attract increasing interest because of their chemical and thermal stability, and the ease of the sulfonation procedure. Some of the proposed polymers are sulfonated polysulfone (SPSU) [134] sulfonated poly(phenylene oxide) (SPPO) [135] sulfonated poly-(ether ether ketone) (SPEEK) [136] poly(phenylquinoxaline) (PPQ) [137] and poly(benzeneimidazole) (PBI) [138],... 

Wholly aromatic polymers are thought to be one of the more promising routes to high performance PEMs because of their availability, processability, wide variety of chemical compositions, and anticipated stability in the fuel cell environment. Specifically, poly(arylene ether) materials such as poly-(arylene ether ether ketone) (PEEK), poly(arylene ether sulfone), and their derivatives are the focus of many investigations, and the synthesis of these materials has been widely reported.This family of copolymers is attractive for use in PEMs because of their well-known oxidative and hydrolytic stability under harsh conditions and because many different chemical structures, including partially fluorinated materials, are possible, as shown in Figure 8. Introduction of active proton exchange sites to poly-(arylene ether) s has been accomplished by both a polymer postmodification approach and direct co-... 

The most common way to modify aromatic polymers for application as a PEM is to employ electrophilic aromatic sulfonation. Aromatic polymers are easily sulfonated using concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, or sulfur trioxide (or complexs thereof). Postmodification reactions are usually restricted due to their lack of precise control over the degree and location of functionalization, the possibility of side reactions, or degradation of the polymer backbone. Regardless, this area of PEM synthesis has received much attention and may be the source of emerging products such as sulfonated Victrex poly (ether ether ketone). 

Similarly, polysulfone has been sulfophenylated by lithiation and anionic reaction with 2-sulfobenzoic acid cyclic anhydride (Figure 12). This provides another method to modify polysulfones by attaching pendant sulfonated phenyl groups via ketone links. It would be interesting to see if the phase separation in these materials was affected by the additional functionality of the ketone or the pendant attachment of the sulfonic acid, as opposed to direct attachment of ionic groups to the aromatic polymer backbone. 

Aromatic polymers such as PS are readily attacked by chlorine bromine, concentrated sulfuric acid, and nitric acid. These reactions do not decrease the degree of polymerization of the polymers. Aromatic polymers with stiffening groups, such as PPO, polyarylsulfone, polyarylether ketone (PEEK), and polyphenylene sulfide (PPS), are more resistant to attack by corrosives than those with flexibilizing groups. 

In recent years, remarkable progress has been made in the syntheses of aromatic and heterocyclic polymers to search a new type of radiation resistant polymers. Sasuga and his coworkers extensively investigated the radiation deterioration of various aromatic polymers at ambient temperature [55-57] and reported the order of radiation resistivity evaluated from the changes in tensile properties as follows polyimide > polyether ether ketone > polyamide > polyetherimide > polyarylate > polysulfone. 

It was through such research that ICI s PEEK (polyether ether ketone), one of the first high-performance aromatic polymers, was put on sale, as well as Du Pont s aramide fibers Nomex and Kevlar, more resistant than steel in like volume. 

A full spectrum of licensed petrochemical technologies is featured. These include manufacturing processes for olefins, aromatics, polymers, acids/salts, aldehydes, ketones, nitrogen compounds, chlorides and cyclo-compounds. Over 30 licensing companies have submitted process flow diagrams and informative process descriptions that include economic data, operating conditions, number of commercial installations and more. 

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... 

A potentially valuable characteristic of poly(ether-ketone-carborane)s is that they display enormously enhanced char-yields (up to 95% on pyrolysis in air), compared to the yields obtained from analogous all-aromatic polymers.7 This behaviour suggests that carborane-based polyketones such as 7 could eventually find application as fire-retardants and as precursor polymers for carbon-ceramic materials. 

Poly(ether ketone) (PEK) 1 is a crystalline high-performance aromatic polymer. It can be prepared in solution from the condensation of 4,4 -dihydroxybenzophenone with 4,4 -difluorobenzophenone, in the presence of anhydrous potassium carbonate, using diphenylsulfone as solvent at... 

Poly(arylene sulfone)s and poly(arylene ketone)s are important engineering thermoplastics, and display high Tg-values, high thermal stabilities, good mechanical properties, and an exceptional resistance to both oxidation and acid-catalyzed hydrolysis. It is only during the past decade that the sulfonated aromatic polymers have been considered to be well-suited as PEM candidates for fuel cells [61-64]. 

Energy transfer. To model this mechanism of stabilization, a reaction (number 50, Table I) was included to allow for quenching of the excited ketone by an additive (Ql) with a rate constant comparable to the upper limit for diffusion of a small molecule in a polymer matrix. Figure 8 shows that up to 1M concentration (about 8 wt-%) of quencher had minimal effect on the time to failure (5% oxidation). This assumes completely random distribution of both the excited ketones and the stabilizer as in the calculation of Heller and Blattman (34). Such a bi-molecular process is too slow to compete with the fast unimolecular reactions of the excited ketone, and thus stabilization by such transfer is predicted to be ineffective in polyethylene. Allowance must be made, however, for special cases in which the excitation energy can effectively migrate (e.g., in some aromatic polymers), in which case the bimolecu-lar process may become competitive with the other chemical processes from the excited states. 

Polyaryletherketones (PAEK) are aromatic polymers with ether and ketone linkages in the chain, viz. PEK, PEEK, PEEKK, etc. Polyetheretherketone (Victrex PEEK), [-( )-C0-( )-0-( )-0-]jj, was commercialized in 1980 (Tg = 143°C, T = 334°C). Commercial blends of PEEK include, Sumiploy PEEK/PES/PTFE, PEEK/LCP, Cortem PEEK/ LTG, etc. Evolution of PEEK blends technology is outlined in Table 1.73. 

Four major bands at ca. 30 ppm (aliphatic C), ca. 80 ppm (C bound to oxygen), ca. 130 ppm (aromatic C) and ca. 170 ppm (carboxyl C) dominate typical spectra. In addition, a small peak at around 200 ppm occurs in many aquatic humus samples it has been assigned to carbonyl carbon. Leenheer et al. (1987) compared the C NMR spectra of unaltered and chemically modified aquatic humic materials to suggest that aromatic a-ketones of the acetophenone type were the most abundant types of carbonyl structures in these polymers. 

The chemistry and technology of aromatic polyether ketones may be considered as an extension to those of the polysulfones [58]. The two polymer classes have strong structural similarities, and there are strong parallels in preparative methods. 

The electrophilic route for the production of aromatic polyether ketones involves the use of Friedel-Crafts catalysts. AICI3 is used as a catalyst for the polymerization of p-phenoxybenzoyl chloride as such, or p-phenoxy-benzoyl chloride or terephthaloyl chloride and 1,4-diphenoxybenzene to give a PEK. A PEEK is obtained by the use of p-phenoxyphenoxybenzoyl chloride, respectively. The process is carried out at low temperamres, such as 0-30°C. Due to the heterogeneous nature of this reaction, generally undesirable lower molecular weight polymers are produced. 

In contrast to PTK materials, the addition of sulfone groups to the polymer minimize the problems. When a 4,4 -dihalobenzophenone as a di-halogenated aromatic compound is combined with a 4,4 -dihalodiphenyl sulfone followed by their reaction with an alkali metal sulfide, an aromatic thioether ketone/thioether sulfone random copolymer can be obtained with a high molecular weight. 

Chemical Resistance - PBS is an amorphous aromatic polymer and as such tends to bestable towards aqueous solutions but susceptible to attack from certain polar organic solvents. PBS resists attack from acids, alkalis, oils, fats, greases, petroleum and aliphatic hydrocarbons and alcohols. It does however suffer from stress cracking in certain ketones, esters and aromatic hydrocarbons, and dissolves in the more polar solvents such as dimethyl farmamide and some chlorinated hydrocarbons. Because of the solubility of the material it can be applied as a lacquer or solvent cast into thin film. 

Colgupoum, H. M., Lewie, D. F. (1988). Synthesis of Aromatic Polyester-Ketones in Triflouromethanesulphonic Acid. Polym, 29(10), 1902. 

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