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.

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Cinnamyl bromide product: cinnamyl bromide

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