1. Polymer Research Institute/Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja‐dong, Pohang, 790‐784 Korea;2. Industrial Materials R/D, LG Chemistry, Cheongju, Korea;3. Optoelectronics Group, Cavendish Laboratory, Cambridge University, UK;4. Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Oryongdong, Bukgu, Gwangju, 500‐712, Korea;5. School of Materials Science and Engineering, Seoul National University, San 56‐1, Shillim‐Dong, Kwanak‐Gu, Seoul, 151‐744, Korea;6. Polymer Research Institute/Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja‐dong, Pohang, 790‐784 KoreaPolymer Research Institute/Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja‐dong, Pohang, 790‐784 Korea. Fax: +82‐54‐279‐2399
Abstract:
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 · 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 °C 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 ≈10 µm 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/BAlq3/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 · cm?2, respectively, at the same voltage of 12 V.
