Poly benzimidazole s

The technical production of poly(benzimidazole) (PBI) is also carried out in two steps. In the first step an aromatic tetramine is condensed with the diphenyl ester of an aromatic dicarboxylic acid at 220-260 °C, yielding a poly(amino amid) with elimination of phenol. Ring closure with elimination of water occurs in the second step (solid-phase polycyclocondensation), conducted at 400 °C and yielding the polybenzimidazole (experimental procedure, see Table 2.3). 

The resulting polybenzimidazole is amorphous and shows a very high glass transition temperature of 425 °C. It is highly flame resistant. Therefore, FBI fibers that are spun from solution, are used for the production of fireproof protection clothes and also for fabrics of airplane seats. 

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Fluorine-containing aromatic poly(benzimidazole)s are synthesized by direct polycondensation of 2,2-bis(4-carboxyphenyl)-l, 1,1,3,3,3-hexafluoropropane (15) with 3,3 -diaminobenzidine tetrahydrochloride (23) (Scheme 13) and 1,2,4,5-benzenetetramine tetrahydrochloride (24) (Scheme 14) in PMMA or PPA.24... 

Poly(benzimidazole)s possess excellent thermal stability, flame resistance, and outstanding chemical resistance. The solubility of hexafluoroisopropyli-dene-unit-containing poly(benzimidazole)s is remarkably improved.24 They are readily soluble in strong acids such as formic acid, concentrated sulfuric acid, and methanesulfonic acid and in aprotic polar solvents such as DMAc and NMP. The polymer from tetramine (23) is soluble even in m-cresol and pyridine. 

Aromatic poly(benzimidazole)s (PBI)s were synthesized by Vogel and Marvel in 1961 [1,2]. It was soon discovered that these polymers have excellent thermal and oxidative stability. Therefore a growing interest developed. 

Amino monomers can in general be classihed as those that deliver AA or AA/BB type polymers, i.e., poly(benzimidazole)s or poly(benzobisimidazole)s [3]. This is shown schematically in Figure 16.1. 

Figure 16.1 Types of aromatic amino monomers. Table 16.1 Monomers for Poly(benzimidazole)s...

The second edition is an npdate of the most recent literatnre. has been added. In addition, a new chapter, dealing with poly(benzimidazole)s... 

Sukumar P R, Wu W, Markova D, tinsel 0, Klapper M and Mtlllen K (2007), Functionalized poly(benzimidazole)s as membrane materials for fuel cells , Macromol Chem Phys, 208,2258-2267. 

Finally, it should be mentioned that the aromatic polyimides were the forerunners of a diversified group of thermostable polymers having heterocyclic moieties in their repeat units, for example, poly(benzimidazole)s, poly(benzox-azole)s, poly(benzthiazole)s, poly(benzobisthiazole)s, poly(l,3,4-oxadiazole)s. 

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