A fluorescent copolyimide containing perylene, fluorene and oxadiazole units in the main chain

A quaternary copolyimide containing perylene, fluorene and oxadiazole units in the backbone, named as OPFFx, was designed and synthesized by a one-step polycondensation under high temperature. The successful polymerization was proved by both elemental analysis and FT-IR spectra. Weight average molecular weight of the polymer was in the range of 2.02-3.09 × 104 as measured by GPC. OPFFx with low oxadiazole content has good solubility in common organic solvents such as chloroform and tetrahydrofuran. Thin film of OPFFx could be prepared by directly spin-coating of its chloroform solution onto quartz glass. The polymer showed high thermal stability and the temperature of 10% weight loss was higher than 494 °C as measured by TGA in nitrogen, and no apparent glass transition temperature was observed from DSC measurement in nitrogen up to 350 °C. The film of OPFFx irradiated by ultraviolet light emitted strong reddish-orange fluorescence. Cyclic voltammetry measurement indicated that OPFFx could be easily reduced (n-doped). Thus, the polymer may potentially be used as a thermal stable light-emitting and electron transporting material for light-emitting diodes.