| 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. |
