Polyfluorenes synthetic methods

R = aikyi or aryi groups, X = Br or i, Y = H or aikyi groups. Figure 11.17 Examples of synthetic methods for polyfluorenes. 

Many synthetic routes are utilized to generate 6,12-functionalized dihydroindeno[l,2-h]fluorenes, typically from 22 or 26. One direct method is base-promoted alkylation of the methylene carbons of 26. For example, lithiation of 26 followed by treatment with 1-bromooctane gave tetrasubstituted 101 (Scheme 29) [80]. Subsequent bromination at the 2- and 8-positions with CuBr/ alumina furnished 102, which could then be polymerized to form polyindeno-fluorene 103 linked at the 2- and 8-positions rather than at the 6- and 12-positions as seen in Scherf s polyindenofluorene 85. Muellen and co-workers foxmd that 103 showed a bathochromic shift in fluorescence compared to polyfluorene (into the visible region) and it formed a liquid crystalline phase at high temperature, possibly making a suitable LED component. 

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