Synthesis, Characterization and Antimicrobial Activity Evaluation of the Polybenzimidazole Derivatives with Different Dicarboxylic Acid Moieties

A series of polybenzimidazole was synthesized by the solution polycondensation reaction of 3,3´-diaminobenzidine (DAB) with dicarboxylic acid derivatives. The synthesized polybenzimidazoles were characterized by using IR, 1H-NMR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA and DSC studies showed that the polybenzimidazoles have good thermal stability and are generally amorphous in nature. Glass transition temperature (Tg) values were found to be in the range of 300-410°C. This is the first detailed study to investigate the antimicrobial activities of the polybenzimidazoles. The synthesized polybenzimidazoles have high antimicrobial activity compared to benzimidazole molecules. It was also found that they are more effective against bacterial species than fungal species. The polymers 2, 5, 6, 7, having -1,3-phenyl, vinyl, -1-OH-3,5-phenyl and 4,4´- oxybisphenyl rings, showed remarkable activity against tested bacterial species (MIC = 32-500 μg/mL). Among these polymers, the polymers 6 and 7 having additional electronegative moiety have the highest activity against tested bacterial species.