Fluorene-based polymers

M Bernius, M Inbasekaran, E Woo, W Wu, and L Wujkowski, Fluorene-based polymers — preparation and applications, J. Mater. Sci. Mater. Electron, 11 111-116, 2000. 

B. Liu, W.-L. Yu, Y.-H. Lai, and W. Huang, Blue-light-emitting fluorene-based polymers with tunable electronic properties, Chem. Mater., 13 1984-1991, 2001. 

Fig. 1 Band offsets, i.e., relative HOMO/LUMO energies, for two representative type II polymer junctions, i.e., the TFB F8BT and PFB F8BT heterojunctions. Both are fluorene-based polymer materials [26,33]. In this chapter, we focus on the TFB F8BT junction.

Fluorene-based polymers have been used as the emissive element in commercially available polymer displays, announced in October 2000.1 The reported displays have a start emitting light below 2.5 V and an efficiency as high as 16 lm/W, and can emit 10 times the brightness of a CRT television screen at just 5 V. This achievement is all the more remarkable given that the synthesis of polyfluorene was first reported only in 1989.2 Ironically, polyfluorene was synthesized shortly before Burroughes et al. reported the discovery of the polymer LED in 1990.3 This pair of discoveries 1 year and half the world apart paved the way for the recent breakthrough. 

Polymer LEDs with copolymers containing dibenzosiloles have been reported in the literature [39,42]. By varying the 3,6-dibenzosilole content in a fluorene-based polymer, superior colour purity and optimum external quantum and luminous efficiencies were obtained (Fig. 5) [39]. Compared to polyfluorene, these copolymers are also stable to thermal annealing. Similar results were reported for a 2,7-dibenzosilole-co-3,6-dibenzosilole polymer [42]. 

Figure 3.4 PLE mappings for the CoMCM SWNTs dispersed in (a) SDBS/D2O and in (b) PFO/toluene, respectively. Reprinted (adapted) with permission from Chen, F. et al, Toward the Extraction of Single Species of Single-Walled Carbon Nanotubes Using Fluorene-Based Polymers. Nano Letters, 2007. 7(10) pp. 3013-3017. Copyright (2007) American Chemical Society.

Not only limited to the PFO polymer, another fluorene-based polymer poly(9,9-dioctylfluorene-a/t-benzothiadiazole) (F8BT) is also able to discrimi-nately wrap SWNTs with larger diameters such as a (15,4) tube." It has been suggested that a stable exciplex between poly[(9,9-dioctyl-fluorenyl-2,7-diyl)-co-(bithiophene)] (F8T2) and SWNTs exists, in which the energy level matching between SWNTs and fluorene-based polymers is responsible for the chirality selectivity. 

R. Xia, G. Heliotis and D. D. C. Bradley, Fluorene-based polymer gain media for solid-state laser emission across the full visible spectrum, Appl. Phys. Lett., 82, 3599-3601 (2003). 

Scheme 19.12 Preparation of EDOT-fluorene-based polymer 14.

Polyfluorenes with alkyl substituents at C9 are soluble in conventional organic solvents such as aromatic hydrocarbons, chlorinated hydrocarbons and tetrahydrofuran, which made them useful to prepare thin films for OLEDs. As a consequence many efforts have been undertaken to synthesize a large number of high-molecular-weight, 9-mono-, or disubstituted very pure fluorene-based polymers. 

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