| Summary: | 博士 === 國立成功大學 === 化學工程學系碩博士班 === 94 === Since polymeric light-emitting diodes based on poly(p-phenylenevinylene) (PPV) were reported by Burroughes et al., electroluminescence (EL) from fully-conjugated polymers, main chain polymers with isolated chromophores, side chain polymers with linked chromophores, and polymeric blends also have been extensively investigated.
In this dissertation, we synthesized a series of copoly(aryl ether)s (P1~P8) consisting of electron-transporting segments [bis(3-(trifluoromethyl)phenyl)-1,3,4-oxadiazole (OXD-F), bis(3-(trifluoromethyl)phenyl)-4-(4-hexyloxyphenyl)-4H-1,2,4-triazole (TAZ-F), 2-(3-(trifluoromethyl)phenyl)-5-(4-(5-(3-(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)- 2,5-bis(hexyloxy)phenyl)-1,3,4-oxadiazole (DIOXD), 2,7-bis(3-(trifluoromethyl)phenyl)- 9,9-dihexylfluorene, 4-(4-(hexyloxy)phenyl)-3,5-diphenyl-4H-1,2,4-triazole (TAZ) or 2,5-diphenyl-1,3,4-oxadiazole (OXD)] and hole-transporting segments [1,4-bis(hexyloxy)- 2,5-distyrylbenzene (DSB), bis(styryl)fluorine (DSF) 3,6-distyryl-N-2-ethylhexylcarbazole, or 2,7-distyryl-9,9-dihexylfluorene]. The emissions of P1~P8 are dominated by the hole-transporting fluorophores with longer emissive wavelength via efficient excitation energy transfer. From electrochemical date, electron and hole affinity of P1~P8 can be enhanced simultaneously.
Furthermore, a series of PPV derivatives polymer P9~P18 have also synthesized. Polymers P12 and P13 only possess hole-transporting DSB segments are treated as model polymers. Polymer P10~P11 and P13~P18 consisting of electron- transporting OXD, TAZ, DIOXD segments and hole-transporting DSB segments via different connectors. The connectors between hole- and electron-transporting segments in P9~P10 and P14~P18 can be divided into five categories: (1) 1,4-phenylene for P14, and P16; (2) 1,4-divinylbenzene for P15 and P17; (3) 4,4’-biphenylene for P18; (4) ether spacers for P9; (5) single bonds for P10 and P11. The effects of connector structures between hole- and electron-transporting segments on polymeric properties were observed and discussed. From optimized semi-empirical MNDO calculations, the adjacent benzene rings between DSB and OXD, TAZ or DIOXD chromophores in P10, P11, P14, P16, and P18 twist about 81o~89o. The large torsion in P10, P11, P14, P16, and P18 significantly limits delocalization of charges between hole- and electron-transporting segments. Accordingly, in P10, P11, P14, P16, and P18, the oxidation and reduction starts at the hole- and the electron-transporting, respectively, like those in P1~P9. The electroluminescences of P9~P18 and corresponding C.I.E. coordinate are also depicted to indicate that incorporating different connectors to these polymers changed their color from blue, green to yellow region.
The thermal, optical, electrochemical, and electroluminescent properties of these polymers were investigated. Optical properties of P1~P18 were investigated by comparing their absorption and photoluminescence spectra with those of compositional model compounds M1~M5, M1~M4 and model polymers P1~P4. Three corresponding end-capped model polymers P12-M~P14-M were also synthesized to evaluate the effect of end groups.
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