Synthesis and electroluminescent properties of fluorene‐based copolymers containing electron‐withdrawing thiazole derivatives

Abstract

We synthesized two fluorene-based copolymers poly[(2,5-bis(4-hexylthiophen-2-yl)thiazolo[5,4-day]thiazole-5,5 0-diyl)-alt-(9,9 0-dioctylfluorene-2,7-diyl)] (PF-TTZT), and poly[(5,5 0-bis(4-hexylthiophen-2-yl)-2,2 0-bithiazole-5,5 0-diyl)-alt-(9,9 0-dioctylfluorene-2,7-diyl)] (PF-TBTT), which contain the electron-withdrawing moieties, thiazolothiazole, and bithiazole, respectively. Through electrochemical studies, we found that these two polymers exhibit stable reversible oxidation and reduction behaviors. Moreover, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PF-TBTT are lower than those of PF-TTZT, and the bandgap of PF-TBTT is smaller than that of PF-TTZT. Thus the bithiazole moiety in PF-TBTT is more electron-withdrawing than the thiazolothiazole moiety in PF-TTZT. Light-emitting devices with indium tin oxide (ITO)/poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate)(PEDOT)/polymer/bis(2-methyl-8-quinolinato)-4-phenylphenolate aluminum (BAlq)/LiF/Al configurations were fabricated. The performance of the PF-TBTT device was found to be almost three times better than that of the PF-TTZT device, which is because electron injection from the cathode to PF-TBTT is much easier than for PF-TTZT. We also investigated the planarity and frontier orbitals of the electron donor-acceptor (D-A) moieties with computational calculations using ab initio Hartree-Fock with the split-valence 6-31G* basis set. These calculations show that TBTT has a more nonplanar structure than TTZT and that the bithiazole moiety is more electron-withdrawing than thiazolothiazole. These calculations are in good agreement with the experimental results. V

Polymer/clay nanocomposites based on aliphatic–aromatic polyamide containing thiazole ring and new organomodified nanosilicate layers: Synthesis, characterization, and thermal properties study

“…In recent decades, polymers containing thiazole which is a rigid five‐membered heteroaromatic ring containing sulfur atom and one —C==N—C— bond have attracted many attention for their unique optical properties and optoelectronic applications . Polymers containing thiazole have unique properties and comprehensive applications in advanced optoelectronic fields, such as organic field‐effect transistors, electroluminescent devices, and nonlinear optical applications . Thiazole exhibits high thermal and oxidative stability .…”

“…Polymers containing thiazole have unique properties and comprehensive applications in advanced optoelectronic fields, such as organic field‐effect transistors, electroluminescent devices, and nonlinear optical applications . Thiazole exhibits high thermal and oxidative stability . Furthermore, polymers containing thiazole shows high thermal stability and reversible n‐donating properties .…”

Optical and electrochemical properties of polyfluorenes with pyridine–triphenylamine bipolar unit

“…For most conjugated polymers the injection and transport of holes is much more favoured than electrons because of high lowest unoccupied molecular orbital (LUMO) levels. This leads to imbalance of charge‐carrier transport . To achieve high efficiency, balanced rates of injection and transport of both electrons and holes in polymeric materials are essential.…”

Prostate‐specific antigen screening among young men in the United States

“…The injection and transport of hole is much favored than electron because of high LUMO levels in most conjugated polymers. High injection and transport barrier for electron leads to imbalance of charge‐carrier transport 24. Therefore, it is not only important to decrease the barriers of charge injection from the opposite contacts but also necessary to balance the injection and transport rates of opposite charges.…”