Conjugated polymer general properties

In this contribution, we discussed effects of disorder on the electronic properties of quasi-one-dimensional Peierls systems, like the conjugated polymer fraus-poly-acetylene. Since polymer materials generally are rather disordered and the effect of disorder on any quasi-one-dimensional system is strong, a proper description of these materials requires consideration of such effects. 

In general. Figure 9-2 b to c show strategies to make conjugated polymers more proeessible but it must be noted that the different synthetic approaches do not only result in different degrees of (a) chemical purity but also alter (b) the physical properties due lo intrinsic differences. Compared to a pure conjugated... 

The rest of this chapter will focus primarily on results using the soluble PPV-based polymer MEH-PPV. The results obtained for MEH-PPV are typical of the conjugated polymers used in LEDs. The models and results presented are generally applicable. They describe the operation of a wide range of polymer LEDs if the appropriate polymer film properties arc used. 

The materials properties of conjugated polymers have improved significantly over the last five years, especially because of major developments in controlled synthesis and processing technology12 13. Recent overviews of the general state-of-the-art can be found in the... 

Conjugated polymers like poly(l,4-phenylene-vinylene), PPV, or more generally Poly(arylene-vinylenes), PAVs have evoked considerable interest as electrically conductive and nonlinear optical materials. More recently, electroluminescence properties of PPV have attracted substantial attention, since it was first reported in 1990. Direct synthesis of PPV has been limited by its insolubility. Hence, the most commonly used routes are based on soluble polymer precursors or soluble conjugated precursors. The latter process is also commonly referred to as the sulfonium-based polyelectrolyte precursor route. PPV thin films from these solution-based routes, however, have problems related to contamination by solvents and oxidative defects in the polymer. C VP is an alternate method for the deposition of high quality thin films of PPV. Reported first by Iwatsuki et al., it was investigated for electroluminescence applications by Staring et al. ... 

Conjugated polymers satisfy these requirements and have thus emerged as the most widely studied materials for their susceptability. Some of the examples of conjugated polymers, that have been studied for their third order NLO properties, are polydiacetylenes, poly-p-phenylenevinylenes and polythiophenes. However, CVD has only been used in the case of poly-p-phenylenevinylenes (PPV) [section 3.4], although values have not been reported. An excellent review of third order nonlinear optical properties of PPV in general, can be found in literature. Recently, McElvain et al. ° reported the values of CVD polyazomethines to be... 

In the past, little work has been directed to the synthesis of new conjugated polymers, since the activities of the chemists have been concentrated on improving the synthetic accessability of already known conjugated polymers and on establishing structure-property relationships. Remarkable exceptions to this general statement are poly(phenylene sulfide-phenyleneamine) (PPSA) 139 and poly(phenylene sulfide-phenyleneamine-phenyleneamine) (PPSAA) 140 recently synthesized by Mullen et al. (see chart 21) [198]. The polymers represent two... 

In fact, for conjugated polymers, E results from a combination of a and tr bonds (the latter being equal to t ) and E,j is dominated by the interchain transfer integral, Thus, the inequalities imply that, quite generally, the conductivity and the mechanical properties will improve in a correlated manner as the degree of chain alignment is Increased. This prediction is in excellent agreement with data obtained from studies of the poly(3-alkylthiophenes), the poly(phenylene vinylenes), poly(thienylene vinylene) and polyacetylene [27]. 

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