Phenol → Benzimidazole

Participants

Reaction Conditions

Reaction Steps

A polymerization flask equipped with nitrogen inlet and outlet tubes and mechanical stirrer was thoroughly flamed and purged with nitrogen. To this was added a mixture containing 5.0 g (14.5 mmole) of 2-[p-carbophenoxyphenyl]-5,6-diaminobenzimidazole and 25 g of diphenyl sulfone. The reaction flask was then slowly heated to 250° C and maintained at that temperature for 6 hours. During this time, phenol sublimed from the reaction mixture, and a precipitate formed. The flask was cooled to 125° C and the polymer suspension poured into 500 ml of methanol. The polymer thus precipitated was collected on a filter frit, washed several times with small portions of methanol, and dried. Reprecipitation from methane sulfonic acid into methanol, followed by successive washings with 5% ammonium hydroxide, methanol and benzene, yielded 2.9 g of benzimidazole polymer as a dark tan powder, exhibiting an inherent viscosity of 1.1 dl/g in methane sulfonic acid (0.35 g/dl).

Provenance & Evidence