Synthesis and light-emitting properties of new polyimides containing ethynylene units in the main chain

Two new polyimides (ODA-PI and HDA-PI) having 1,4-phenylenediethynylene unit and octyloxy groups were synthesized. Judging from inherent viscosities of their precursor PAAs (1.42 and 1.62 dL center dot g(-1)), the two PIS were very high in molecular weight. Casting and thermal imidization of PAAs results polyimides with good-quality films. They were stable up to 364 OC and showed no crystallites. UV-vis and PL spectra in NMP solutions of both PIs showed maxima at 442 and 501 nm, respectively, while PL spectra in approximate to 10 mu m thick films exhibited a maximum at 540 nm. CV indicates that two PIS were electrochemically active in redox region. The devices with construction of ITO/PEDOT/PIs/BAlq(3)/LiF/Al exhibited turn-on voltages of 6.5 V in ODA-PI and 7.5 V in HDA-PI and emitted a bright bluish-green light. ODA-PI and HDA-PI showed maximum luminescence of 256 and 316 cd center dot cm(-2), respectively, at the same voltage of 12 V.