Benzimidazole polymers from aldehydes and tetraamines

Abstract

A new method for the preparation of benzimidazole polymers is described. The solution polymerization of aromatic tetraamines with isophthalaldehyde bis bisulfite adduct in N,N‐dimethylformamide (DMF), N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (MP), and dimethyl sulfoxide (DMSO) produced polybenzimidazoles with viscosities (ηinh) in the range of 0.3–0.5 measured in formic acid solution. Also a model compound study with benzaldehyde, benzaldehyde diethyl acetal, and benzaldehyde bisulfite adduct with o‐phenylenediamine was carried out. The results showed that the reaction of benzaldehyde bisulfite adduct with o‐phenylenediamine in DMAc as the solvent gave quantitative yields of 2‐phenylbenzimidazole. Excellent yields of 2‐phenylbenzthiazole, 2‐phenylbenzoxazole, and 2‐pyridylbenzimidazole were also obtained with the benzaldehyde bisulfite adduct and picoline‐2‐carboxaldehyde bisulfite adduct with o‐aminothiophenol, o‐aminophenol, and o‐phenylenediamine. The reaction conditions for the preparation of the polymers and the model compounds are very mild and the reaction times range from 15 min to 1 hr for the model compounds and 3–5 hr for the polymers. Longer reaction times did not increase the viscosities of the polymers to any extent.

Solution polymerization of polybenzimidazole

“…This was attributed to the formation of the imines which were previously observed and reported by Higgins and Marvel. 27 Finally, polymerization experiments using IBA and TAB were conducted and shown by 1 H NMR, TGA, and DSC to produce m-PBI which was studied in further detail and reported herein.…”

“…27 We studied the reaction of the bisulfite adduct of benzaldehyde with o-phenylenediamine in DMAc via GC/MS. GC/MS analysis revealed a very efficient reaction with high yield of 2-phenylbenzimidazole and no unwanted byproducts as shown in Figure 3.…”

“…In 1970, Higgins and Marvel had reported the use of tetraamines with the bisulfite adducts of aldehydes to produce PBI directly in dimethyl acetamide (DMAc). 27 Though small molecule studies indicated this method was promising for the synthesis of PBI, the polymerizations were conducted at 1 wt % polymer and high inherent viscosity (IV) was never achieved. PBI is commercially produced by PBI Performance Products using a two stage melt/solid phase polymerization method by condensing diphenyl isophthalate (DPIP) with tetraaminobiphenyl (TAB) to produce poly(2,2'-m-phenylene-5,5'-bibenzimidazole) (m-PBI).…”

“…Remarkably, when using purified monomer and high (18-22 wt %) polymer concentrations, the polymer IVs obtained under these conditions were significantly higher than previously reported. 27 Additionally, polymerizations could be conducted at much higher monomer charges without polymer precipitation. The higher final polymer solution concentrations are in the range of polymer concentrations used in commercial processes for coating, casting and fiber spinning, thus allowing the direct processing of polymerization solutions without polymer isolation, purification, or lengthy re-dissolution procedures.…”

Poly(2,5-benzimidazole) nanofibers prepared by reaction-induced crystallization

“…Among them, polybenzimidazoles are one of the most successful materials, because of their high chemical resistance, flame retardance, radiation stability and excellent mechanical strength, which is retained over a wide temperature range. [1][2][3][4][5][6][7][8][9][10] Much effort has been devoted to fabricating polybenzimidazoles for practical uses and some of them are now commercially available. 11,12 Polybenzimidazoles do not melt at decomposition temperatures and they are usually soluble only in strong acids such as sulfuric acid and methanesulfonic acid.…”