Since the discovery by Holmes, Friend and coworkers of electroluminescence from conjugated polymers [1], there has been considerable industrial and academic interest in electroluminescent polymers for use as the active materials in light-emitting devices (LEDs) [2,3] or polymer lasers [4]. Obviously if one is to make commercially viable devices then one needs materials that can produce the desired emission colors, with high emission intensity and efficiency, and show good stability. This presents a challenge to synthetic chemists to design and make polymers that meet these criteria. In particular the control of the emission color, of the charge-accepting and transporting properties, which are important for optimizing device efficiency, and of electrical and optical stability, which are vital factors in determining device lifetimes must be addressed. In this chapter an overview is presented of the main methods by which the most important types of electroluminescent polymers can be prepared with an emphasis on how synthetic design can contribute to the meeting of the above-mentioned device-performance criteria. Space does not permit a comprehensive review of all structures or methods, for which the reader is referred to existing reviews [2, 3], but instead representative structures and syntheses are shown.
Poly(arylene vinylene)sPoly(arylene vinyene)s (PAVs) represent the most widely studied group of electroluminescent polymers. The parent compound poly(para-phenylene vinylene) (PPV, 1, Fig. 6.1) [5] is insoluble and so must be processed as a precursor polymer but derivatives such as MEH-PPV (2) [6] with solubilizing alkyl, aryl, silyl, or alkoxy chains show good solubility in organic solvents and so can be readily processed by techniques such as spin casting. By appropriate choice of substituents 215