Synthesis and characterization of conjugated copolymers containing different chromophores in the main chain

• Main Authors: Hung-Ruei Shen, 沈泓睿
• Other Authors: Chien-Chao Tsiang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/22026974797165702355

碩士 === 國立中正大學 === 化學工程研究所 === 92 === A series of novel light-emitting copolymers having well-defined conjugation lengths and different chromophores have been synthesized. The solubility and the optical and electrochemical properties were investigated, and the effects of introducing nonlinear thiophene and 1,3,4-oxadiazole into the main chain were discussed. Single- and multi-layered LED devices fabricated with these copolymers were characterized. In this study, monomer 1(1,4-Bis(4-methylphenyl)benzene) and 3 (2,5-Bis(4-methylphenyl)thiophene) were synthesized by Suzuki cross-coupling reaction and monomer 7 (2,5-Bis(4-methylphenyl)-1,3,4-oxadiazole) were synthesized by cyclodehydration. Copolymers P1, P2 and P3 were prepared via a nucleophilic substitution of halide ions from halogenated monomer 1, 3 and 7 by alkoxide ions and formed a chromophores-nonconjugated alternating structure with well-defined conjugation lengths. TGA and DSC analyses indicated that all copolymers were thermally stable below 215℃ with Tgs higher than 90℃.While P1 is crystalline and has a Tm at 136℃, the others are amorphous materials. From UV/Visible and PL spectra of P1, the extent of intramolecular/intermolecular aggregation were studied. The elevated tail in UV/Visible spectra of P1 implied that very low contents of intramolecular/intermolecular aggregates were formed. With increasing concentrations of P1, the peaks at 542 nm in PL spectra appeared. The λmaxPL of P1 in solid film state was also red-shifted drastically to about 542 nm with a weak shoulder at about 470 nm. These results indicated that intramolecular/intermolecular aggregates of P1 shifted the wavelength to lower energy. By substituting thiophene and 1,3,4-oxadiazole for the middle phenyl ring in the chromophores structures as in P2 and P3, the optical properties and solubility were enhanced. Moreover, the multi-layered devices constructed with P2 and P3 emitted high luminescences 4289 cd/m2 (at 15 V and 110 mA) and 4879 cd/m2 (at 10 V and 51 mA), respectively. Thus, physical properties of conjugated copolymers can be highly different even if the conjugational length is uniform, and intramolecular/intermolecular interactions can lead to the formation of aggregates, which emitted different colors.