Synthesis and photoluminescence properties of polybenzoxazoles containing perylenebisimide functionalized graphene nanosheets via stacking interactions

The stable acidic dispersion of reduced graphene oxide (RGO) is prepared by a non-covalent functionalization method using perylenebisimide-modified fluorinated poly(hydroxyamide) (PTCDA-6FPHA). Then a series of RGO-polybenzoxazole (PBO) composites were prepared by a solution blending method in MSA. The change of perylenebisimide absorption peaks in the UV-Vis absorption spectra indicates that pi-pi stacking indeed occurs between graphene and perylene rings. The conjugation between functionalized RGO and PBO molecular chains increases the conjugation degree of the composite, since the PTCDA-6FPHA-containing perylene rings have a high pi-electron delocalization degree. The energy gap of RGO-PBO composite is 2.72 eV with the absorption edge at 456 nm. The corresponding data of pure PBO film are 2.78 eV and 446 nm, respectively. Moreover, the intensity of the two emission peaks at 442 and 467 nm in the PL emission spectra of RGO-PBO decreases rapidly along with the increase of RGO-PBO ratio. The intensity of the weak emission peak at 622 nm increases with the increase of the RGO-PBO ratio. This behavior can be attributed to the energy transfer between benzoxazole chromophore units and functionalized RGO. Meanwhile, the RGO-PBO composite has outstanding thermal stability.