Polybenzimidazole , reactive

Qing, S., Huang, W., Yan, D. (2006) Synthesis and properties of soluble sulfonated polybenzimidazoles. Reactive and Functional Polymers, 66, 219-227. 

Other Reactive Oligomers - In the mid 1960 s, a reactive oligomeric precursor to a polybenzimidazole (PBI) was available as... 

Olason, G. and D. C. Sherrington, Oxidation of cyclohexane by r-butylhyd-roperoxide and dioxygen catalyzed by polybenzimidazole-supported Cu, Mn, Fe, Ru, and Ti complexes . Reactive and Functional Polymers, vol. 42, Issue 2, 15 November 1999, pages 163-72. 

The molecular size of polybenzimidazoles has in the pertinent literature been expressed in terms of inherent (j7i h) or intrinsic ([ ]) viscosities, determined on sulfuric acid solutions or, less frequently, on solutions in formic acid or aprotic solvents. The effect of structure on viscosity behavior appears to be less pronounced than that of the polymerization methods used and of the monomer sensitivity to the employed reaction conditions. In general, melt polymerizations by Marvel s method give products with higher molecular mass than obtained in solution condensations, which may partly be due to increased end group reactivity and interaction at the much higher reaction temperatures encountered in the former process (Cf. Table 1). Furthermore, monomers like bis(phenoxycar-bonyl)ferrocene, diphenyl tetrafluoroterephthalate, or l,7-bis(phenoxycarbonyl)car-... 

Electro-insulation materials. The retention of dielectric properties in a high-temperature environment, coupled with good corrosion resistance in contact with certain reactive chemicals, suggests excellent possibilities of polybenzimidazole use in electrical insulation and other dielectric applications at high operating temperatures and/or in aggressive chemical environments. Typical applications, hence, can be foimd in special cable and wire insulation, in the manufacture of circuit boards and radomes for supersonic aircraft, as battery and electrolytic cell separators, and as fuel cell frame structural materials. Some recent publications in the patent and technical report literature may serve to illustrate such applications. 

Polystyrene-based resins have been used widely as supports for metal complex catalysts and other reactive species. These polymers, however, have a drawback in their limited thermo-oxidative stability [1,2]. The scope for application is therefore restricted, particularly in polymer-supported transition metal complex oxidation catalysts [3]. Consequently there is a need for the development of polymer supports with a much higher intrinsic thermo-oxidative stability. Polybenzimidazoles and polyimides are likely candidates in this respect. 

In summary of this section, it must noted that, in spite of numerous studies, nowdays we know very little about carbonyl hydrides and other substituted (mixed) carbonyls thermolysis in polymeric systems, as well as in reactive plastics. For example, in some experiments the decomposing metal carbonyls were placed into an epoxide resin heated up to the nanoparticles deposition on the forming polymer surface [121]. It is possible that the highly reactive metal particles in such systems can initiate the epoxy cycle cleavages followed by a three-dimensional space structure formation. Iron carbonyl being decomposed into polybenzimidazole suspension (in transformer oil at 473 K) forms the ferrum nanoparticles (1-11 nm) capable of polymer thermostabization [122]. 

Because the thermal stability of polystyrenes and polymethacrylates is limited to 200°C, continuous use of a polymer-supported reactive species tends to be limited to significantly lower temperatures than this (see polymeric sulphonic acids). There is considerable interest in supporting, in particular, alkene oxidation catalysts on polymers and to operate reactions at temperatures above 200°C. To achieve this, novel thermo-oxidatively stable supports are required and some progress has been made in this direction. More details of specific applications will be given later, but supports based on, for example, polyacrylonitrile [50-52], polyamides [53-56], polysulphone [57, 58], polyaniline [59] and polybenzimidazole... 

N-Substitut0d PBI The NH groups in the imidazole rings are chemically reactive. For some applications, the chemical reactivity can be reduced by, for example, replacement of the hydrogen of the imidazole ring with less reactive substituents such as hydroxyethyl [179], sulfoalkyl [180,181], cyanoethyl [182], and phenyl [183], as well as alkyl, alkenyl, or aryl [184] groups. The methods developed by Sansone et al. [180-184] use a PBI solution in DMAc or 7V-methyl-pyrrilidone. The unsubstituted PBI is first reacted with an alkah hydride to produce a polybenzimidazole polyanion, which is then reacted with a substituted or unsubstituted alkyl, aryl, or alkenyl methyl halide to produce an iV-substituted PBI, as shown in Fig. 4.13. 

Chanda, M., Rempel, G.L. (1989) Polybenzimidazole resin-based new chelating agents uranyl and ferric ion selectivity of resins with anchored dimethylglyoxime. Reactive Polymers, 11, 165-176. 

Poiyphosphazene Biends Blends of sulfonated polyphosphazene, for example, sulfonated poly[bis(3-methylphenoxy)phosphazene] or poly[(bisphenoxy)phosphazene] (see Fig. 29.14) with either an inert organic polymer such as poly(vinylidene fluoride) (Pintauro and Wycisk, 2004 Wycisk et al., 2002) or polyacrylonitrile (Carter et al., 2002) or a reactive polymer (e.g., polybenzimidazole) (Wycisk et al., 2005) have been investigated. The resultant membranes had conductivities of 0.01-0.06 S/cm (in water at 25°C) and equilibrium water swelling from 20 to 60% (at 25°C). Blends of poly[(bisphe-noxy)phosphazene] and polybenzimidazole (where acid-base complexation occurred between the sulfonic acid and the imidazole nitrogen) exhibited good mechanical properties and low methanol permeability. MEAs with this membrane material outperformed Nafion 117 in a DMFC at 60°C with concentrated (5-10 M) methanol feeds. With 1.0 M methanol and 0.5 L/min ambient air at 60°C, the maximum power density was 97 mW/cm and the methanol crossover was 2.5 times lower than that with Nafion 117 (Wycisk et al., 2005). 

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