Polyfluorene copolymers random

Dias FB, Knaapila M, Monkman AP, Burrows HD (2006) Fast and slow time regimes of fluorescence quenching in conjugated polyfluorene-fluorenone random copolymers The role of exciton hopping and dexter transfer along the polymer backbone. Macromolecules 39(4) 1598—1606... 

Several random fluorene-dibenzothiophene copolymers 67a-e [106,107] have been reported. The meta linkage in the dibenzothiophene in copolymers 67a-e hinders the conjugation, resulting in a hypsochromic shift of the emission bands to the deep-blue color region (kmax 420 and 440 nm) [106]. Furthermore, hindered conjugation and hindered n-aggregation suppress the parasitic green emission at 520 nm in the solid state of the polymer, often observed in polyfluorenes. 

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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