Synthesis and fluorescence in solution of polybenzimidazolylphenylenephthalamides

Six polybenzimidazolylphenylenephthalamides (PBIPPA), two meta/para isomers, and four meta/para isomers that had different distances between a benzimidazolyl and the adjacent benzimidazolyl in a polymer chain were synthesized. They were soluble in N,N‐dimethylacetamide. In addition to the fluorescence from the π → π* transition of isolated phenylbenzimidazole, a fluorescence from a chromophore complex in the grand state appeared in the fluorescence spectra, which was observed at higher concentrations. The concentration dependence of the intensity of the fluorescence was investigated in order to learn whether the chromophore complex was intermolecular or intramolecular. It was concluded that the chromophore complex is intramolecular, a conclusion supported by the viscometric results.