Poly Bronsted acids

This concept covers most situations in the theory of AB cements. Cements based on aqueous solutions of phosphoric acid and poly(acrylic acid), and non-aqueous cements based on eugenol, alike fall within this definition. However, the theory does not, unfortunately, recognize salt formation as a criterion of an acid-base reaction, and the matrices of AB cements are conveniently described as salts. It is also uncertain whether it covers the metal oxide/metal halide or sulphate cements. Bare cations are not recognized as acids in the Bronsted-Lowry theory, but hydrated... 

Quantum yield values measured in solution may not necessarily apply to polymer films, the usual environment for practical application of this photochemistry. McKean et al. have adapted the indicator dye method to the measurement of quantum yields for Bronsted acid photogeneration in poly-(4-tert-butoxycarbonyloxystyrene) [20], As with the solution photochemistry of diphenyliodonium salts [71], an inverse dependence of quantum yield on exposure intensity was observed absolute quantum yields from 0.26 to 0.40 were measured at 254 nm, which extrapolate to approximately 0.45 at zero intensity, comparable to the value estimated by Dektar and Hacker [82b] in solution. McKean et al. [20b] note that similar quantum yields in solution and polymer films below Tg have also been reported for photo-Fries rearrangements [84] and photodissociation of diacyl peroxides [85]. 

SCHEME 12.3 Acid catalyzed deprotection of a poly(r T-butoxycarbonyloxy styrene) PTBOCST resists by the strong Bronsted acid formed in the prior photolysis reaction of a PAG. 

Y. Liu, Q. Yu, and Y. Wu. More studies on the sulfonated poly(phenyl-ene oxide)+iniidazole bronsted acid-base polymer electrolyte membrane. J. Phys. Chem. Solids, 68(2) 201-205, February 2007. 

Liu Y, Yu Q, Yuan J, Ma L, Wu Y. Bronsted acid-base polymer electrolyte membrane based on sulfonated poly(phenylene oxide) and imidazole. Eur Polym J 2006 42(9) 2199-203. 

Initially, the cyclization reaction of 2-benzylpent-4-enoic acid 4 was carried out using concentrated sulfuric acid as both the catalyst and the solvent at a temperature below 45 °C. Further, the repetoire of Bronsted acids (used at ambient or higher temperature) has been expanded to include anhydrous hydrogen fluoride (0 °C)," trifluoroacetic acid (toluene, 70 °C or acetic acid, 70 °C), polyphosphoric acid (xylenes, reflux),and anhydrous pyridinium poly(hydrogen fluoride) (room temperature). 

Electrically conductive PTs are prepared by polymerization in an electrolyte in the presence of polymeric compounds with sulfonic acid groups [692]. The electrochemical polymerization of thiophene and Nafion gives a self-supporting film showing a uniform distribution of sulfur across the film and a reversible voltammogram [693]. Alkoxy substituted thiophene derivatives are electro-chemically polymerized in a solvent in the presence of a proton source in the form of a Bronsted acid [694]. The electrochemical preparation of poly-(3-alkyloxythiophene) without a Brdnsted acid has also been studied [695]. 

Alkanes (C1-C5) can be polymerized by treatment with a combination of a strong Lewis acid and a strong Bronsted acid. For example, n-pentane, by reaction with a mixture of chlorosulfonic acid and antimony pentafluoride at 30 °C (18 hours), gave oligomeric branched poly-n-pentane." Some of die polymers derived from the lower alkanes were useful as petrol additives."... 

The authors have found that the ROP of TeMC initiated with H2O or a primary alcohol (e.g., butyl alcohol) in the presence other Bronsted acids such as HCl Et20 proceeded without decarboxylation to give linear poly(TeMC) with Mn= 1000-10 000 and a narrow dispersion index ( 1.15). They postulated that the key feature of this polymerization is the appropriate acidity of the protonic acid, which should be not as high to polymerize the monomer by itself but sufficient to activate the monomer. ... 

Thermal degradation in the presence of a catalyst seems to be an interesting alternative to simple pyrolysis. For example, both polyisobutylene and poly(isobutylene-co-isoprene) were degraded at low temperatures in the presence of both a Bronsted acid and a Lewis acid to yield a,co-dialkenic telechelics (equation 54). Radiolysis of polyisobutylene also yields a,o)-dialkenic telechelics (equation 55). " ... 

Effect of surface Bronsted acidity on the adsorption of a hydrogen-bonding poly(ethylene oxide) (PEO). (From Ref. 31.)... 

Two reports demonstrate that Bronsted (Olah et al., 1999) or Lewis acids (Oakes et al., 1999) may be more reactive in sc C02 than in organic solvents. The isobutane-isobutylene alkylation (eq. 2.2), which is used commercially to increase the octane numbers in automotive fuels, has been demonstrated to occur in sc C02 with several liquid acid catalysts (Olah et al., 1999). Increased selectivity for Cg-alkylates is observed in sc C02 relative to neat acid media when anhydrous HF, pyridine poly(hydrogen fluoride) (PPHF),... 

While catalysts are also used in the production of other types of polymers, the properties of most of these materials are not particularly dependent on the type of catalyst employed. Many poly condensation reactions, e. g. the formation of polyesters, polyamides or urea-formaldehyde resins, are speeded up by addition of some Bronsted or Lewis acids. Since relevant properties of these polymer products, such as their average chain lengths, are controlled by equilibrium parameters, primarily by the reaction temperatures and molar ratios of the monomers employed, and since their linkage patterns are dictated by the functional groups involved, addition of a catalyst has little leverage on the properties of the resulting polymer materials. 

The central heteroatom in the more or less spherical structure is surrounded by metal oxide tetrahedra. The materials are strong acids. Both Bronsted and Lewis acid acidity are present. Various ligands, such as methylpyridines, can coordinate with them.267 Because the complex with ethyl ether is insoluble in ethyl ether, this can be used as a method of isolation. Transition metals, such as Mn(III), in the poly-oxometalate ion can be oxidized or reduced without destroying the polyoxometalate.268 Heteropolymetalates can serve as ligands for transition metal ions.269 As an example, cyclopentadienyltitanium has been inserted in this way.270... 

The poly(alkylene tartrates) are synthesized by melt polymerization. Both Bronsted-Lowry acids and Lewis acids can be used to catalyze the reaction. Bitritto used para-toluene sulfonic acid (pTSA). The resulting polymers were, in general, colored brown, indicating that the alpha-hydroxyls of the tartaric acid may have been oxidized. When tin chloride was used as the catalyst a lightly colored polymer was formed, indicating that some oxidation probably occurred. Upon purification of the product however, the yellow color was removed. It appears that more favorable reaction conditions exist when tin chloride is used as the catalyst and thus it has become the catalyst of choice for future syntheses. 

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