Rigid-rod polybenzoxazoles containing perylene bisimide: Synthesis, structures and photophysical properties

A novel perylene bisimide dye bearing carboxylphenylene substituents on the imide N atoms was synthesized and four conjugated copolymers containing different contents of perylene bisimide dye were synthesized via PPA/P₂O₅ copolymerization method. The structures of the four copolymers were characterized by FTIR, elementary analysis, ¹H-NMR and XRD. The copolymers showed good thermal stabilities but poor solubilities due to the high rigidity of the backbone. The photophysical characteristics of the copolymers were investigated by UV-Vis and PL spectra in solutions and films. Because of the conformational change of perylene bisimide chromophore, the absorptions of perylene bisimide core in copolymers showed a large blue-shift (56 nm) compared to that of the perylene monomer. In PL experiments, when exciting the benzoxazole, an obvious fluorescent quenching was observed in all copolymers, which can be attributed to the energy transfer from benzoxazole units to perylene bisimide fragments and fluorescence quenching. With increasing perylene content, the copolymers turned to layered and friable. The XRD test showed that the interchain distances increased slightly with increasing perylene content. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010