Polyfluorene copolymers groups

Zhou et al. synthesized polyfluorenes with phosphonate groups in the side chain and demonstrated their use as metal ion sensors, especially for Fe ". Kim et al. were able to detect 1.5 nM K using polyfluorene copolymers and a molecular beacon ° (Chart 5.7). 

The polymers used in this chapter are all polyfluorene derivatives. They are ABAB copolymers with A being the fluorene group shown in Fig. 2.4(a). Due to their high chemical stability, flexible chemistry and good charge transport and luminescence properties, polyfluorenes are very common materials for polymer optoelectronics and have been used to make highly efficient LEDs [26, 13] as well as good photovoltaic diodes [27, 28] and transistors [29]. Table 2.1 lists the abbreviated and full names of all the polymers that appear in this chapter. The chemical structures of each of the polymers are displayed in Fig. 2.4. 

Andersson and coworkers have prepared solar cells based on blends of poly(2,7-(9-(2 -ethylhexyl)-9-hexyl-fluorene)-fl/t-5,5-(4, 7 -di-2-thienyl-2, l, 3 -benzothiadiazole) (223) and PCBM [416]. The polymer shows a Amax (545 nm) with a broad optical absorption in the visible spectrum and an efficiency of 2.2% has been measured under simulated solar light. The same group has also reported the synthesis of low bandgap polymers 200 (1 = 1.25 eV) and 224 (1 = 1.46 eV) which have been blended with a soluble pyrazolino[70]fiillerene and PCBM, respectively, to form bulk heterojunction solar cells of PCE of 0.7% [417] and 0.9% [418]. Incorporation of an electron-delident silole moiety in a polyfluorene chain affords an alternating conjugated copolymer (225) with an optical bandgap of 2.08 eV. A solar cell based on a mixture 1 4 of 225 and PCBM exhibits 2.01% of PCE [419]. 

An industrial group have reported obtaining efficient red, green, and blue emission from polyfluorene-based alternating copolymers prepared by Suzuki polycondensation, but without publishing their structures [270,271]. 

Three principal types of Suzuki polymerizations for polyfluorenes have been developed for homopolymers and copolymers by Dow, Cambridge Display Technology (CDT), and Covion, which was merged with Merck. Early detailed experimental procedures were reported in the patent literature (Scheme 5.5 and Table 5.2). These and other groups have used these polymerizations for numerous poly fluorene derivatives (Table 5.3). 

The described synthesis of polyfluoren homopolymers allows also the design of alternating copolymers. Instead of the 2,7-dibromofluorene a variety of dibromoarenes ean be used in the Pd-catalyzed coupling polymerization reaction. An important group of... 

The MEM analysis of time-resolved fluorescence decays of several copolymers is shown in Fig. 15.18a. For the homopolymer PF2/6, only a narrow distribution is observed around 360 ps. However, for copolymers PF/FLx, with different fractions of fluorenone residues, distributed randomly along the polymer chain, the distribution at 360 ps is accompanied by two additional peaks. These are observed around 20 and 100 ps as a result of quenching of polyfluorene emission, due to energy transfer from the fluorene to the fluorenone sinks. Figure 15.18b shows the fluorescence decay of the copolymer labelled with 25 % of fluorenone groups, analysed with a sum of three exponential functions. Note the good agreement between MEM and multiexponential analysis [91]. 

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