Bridged polyphenylenes -: from polyfluorenes to ladder polymers

This chapter reviews the synthesis of polymers based on bridged phenylenes for use in electronic applications such as blue-light-emitting diodes and polymer lasers. We show how the optoelectronic properties may be tuned by varying the amount of bridging between one bridge per two phenylenes in polyfluorenes through to completely bridged ladder-type polyphenylenes, and by changing the nature of the substituents at the bridgeheads. Of particular importance is the suppression of undesirable long wavelength emission by controlling interchain interactions and choosing synthetic methods so as to hinder or prevent the formation of emissive defects. The electroluminescence efficiency of these materials can also be enhanced by the use of charge-transporting substituents. Copolymerisation with lower band-gap units enables tuning of the emission colour across the entire visible range.