Poly 5-amino-2- benzimidazole

Fu, Y. Z., Manthiram, A. and Guiver, M. D. 2007. Acid-base blend membranes based on 2-amino-benzimidazole and sulfonated poly(ether ether ketone) for direct methanol fuel cells. Electrochemistry Communications 9 905-910. 

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). 

Govindaraj B, Sarojadevi M. Synthesis and characterization of poly (imide-benzimidazole) hybrid nanocomposites using nano-cluster of octa-amino functionalized polyhedral oligomeric silsesquioxane. Polym Compos 2013 34(6) 825-33. 

A new method has been developed for the synthesis of aromatic diamines containing A-phenyl benzimidazole rings. The polymers softened in the region of 320—450 °C. Poly(p-phenylene terephthalamide) from the vapour phase apparently produces coatings with exceptionally good oxygen barrier properties. Chelate-forming heterocyclic polyamides, poly(amino)benzoxazoles have also been synthesized. ... 

Fu et al. [11] reported the acid-base blend membranes based on 2-amino-benzimidazole (basic polymer) and sulfonated poly(ether ether ketone) (SPEEK) (acidic polymer) for direct methanol fuel cells. A novel polymer, polysulfone-2-amide-benzimidazole (PSf-ABIm), using carboxylated polysulfone and 2-amino-benzimidazole was synthesized for this purpose. The blend membrane of SPEEK/PSf-ABIm showed high performance a s represented by Figure 1.12. The blend membrane with 3 wt% PSf-ABIm was evaluated continuously for 120 h and little or no decline in performance was found after 120 h. On the other hand, the Nafion 112 membrane standard was observed to have a decline in performance due to a much higher amount of methanol crossover. 

These s.c. poly[(benzoylene)-s-triazoles] have poorly defined structure since the cyclization reaction is incomplete. Since the photoconductivity is higher when a substantial amount of unreacted amino groups are left in the structure these polymers and oligomers could be classified as polymers with photoconductive amino group. Voishchev et al.4i recently reported photoconductive properties of poly-[N-phenyl)benzimidazoles] such as... 

Later, it was established that rigid-chain PPI can also show solubility in organic solvents, such as p-chlorophenoL It was reported that soluble rigid-chain poly(naphthalenecarboximides) can be prepared under conditions similar to those mentioned previously [15]. Bulycheva and co-workers [5] synthesised PPI on the basis of 5-amino-2-(p-aminophenyl)benzimidazole (Figure 1.1). 

The early work by Sweeny, Kwolek, and others demonstrated that progress in this area of technology was the result of a constant trade-off between properties and processability. This is very likely the reason why after half-a-century of research only four compositions have reached commercial stage poly(w-phenylene isophthalamide) (MPDI), PPTA, copoly(p-phenylene/3,4 -diphenyl ether terephthalamide) (ODA/PPTA), poly[5-amino-2-(p-aminophenyl)benzimidazole terephthalamide] (SVM), and its copolymers. 

Mallakpour S, Dinar M. Straightforward and green method for the synthesis of nanostructure poly(amide-imide)s- containing benzimidazole and amino acid moieties by microwave irradiation. Polym Bull 2013 70(3) 1049-64. 

Mallakpour S, Dinari M. Novel nanostructure amino acid-based poly(amide-imide)s enclosing benzimidazole pendant group in green medium fabrication and characterization. Amino Acids 2012 43(4) 1605-13. 

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...

Poly(benzimidazoles) are produced from dicarboxylic acids and aromatic tetramines. Commercially, 3,3 -diaminobenzidine tetrahydrochloride and diphenyl isophthalate are preferentially used. The diphenyl ester is used because (a) the free acids decarboxylate under the high reaction temperatures of 250-400 C (b) the acyl chlorides react too fast, making ring closure difficult and (c) the amino groups are partially methylated if the methyl esters are used. The hydrochloride is used because it is more stable to oxidation than the free amine itself. The polycondensation is carried out in two stages. A prepolymer. A, is formed in the first stage with foaming and phenol elimination ... 

Poly(benzimidazoles) have become commercially important. Whereas polyimides contain two carboxyl groups per amine group, two amine groups are allowed to react with a carboxyl group in poly(benzimidazole) manufacture. Diphenyl esters are used as dicarboxyl compounds, since (a) the free acids decarboxylate under the reaction conditions (250°C at first, subsequently 400°C), (b) the acyl chlorides react too quickly, so that ring closure becomes difficult, and (c) with methyl esters, the amino groups become partially methylated. Moreover, eliminated phenol can easily be washed out. Typical materials are 3,3 -diaminobenzidine and diphenyl... 

Scheme 8.1. Most important aramid structures of commercial importance MPDI = poly()Urphenylene isophthalamide) PPTA = poly(p-phenylene terephthalamide) ODA-PPTA = copoly(p-phenylene/3,4 -diphenylether terephthalamide) SVM = poly[5-amino-2(p-aminophenyl)benzimidazole terephthalamide].

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