Poly electronic structures

Both theoretical and experimental evidence suggest that the precise nature of the charge carriers in conjugated polymer systems varies from material to material, and it is still a subject of debate in many cases. A discussion of the various theoretical models for the electronic structure of conjugated polymers is given below, using polyacetylene and poly(paraphenylene) as examples. More detailed information on these materials and the applicability of these theoretical models is given in subsequent sections. 

This first example of the utility of quadrupolar nuclei as sources of information about nano-semiconductors showed that MAS-NMR could identify a poly type that is unstable in the bulk. A second example will show that information about changes in the electronic structure of nanocrystals as a function of synthesis and treatment conditions, as well as information about different polytypes, can be obtained via measurement of Knight shifts and chemical shifts. In this extensive study 69Ga... 

M. Fahlman, M. Logdlund, S. Stafstrom, W.R. Salaneck, R.H. Friend, P.L. Burn, A.B. Holmes, K. Kaeriyama, Y. Sonnoda, O. Lhost, F. Meyers, and J.L. Bredas, Experimental and theoretical studies of the electronic structure of poly(p-phenylene vinylene) and some ring-substituted derivatives, Macromolecules, 28 1959-1965, 1995. 

For instance, poly-p-phenylenes in their doped states manifest high electric conductivity (Shacklette et al. 1980). Banerjee et al. (2007) isolated the hexachloroantimonate of 4" -di(tert-butyl)-p-quaterphenyl cation-radical and studied its x-ray crystal structure. In this cation-radical, 0.8 part of spin density falls to the share of the two central phenyl rings, whereas the two terminal phenyl rings bear only 0.2 part of spin density. Consequently, there is some quinoidal stabilization of the cationic charge or polaron, which is responsible for the high conductivity. As it follows from the theoretical consideration by Bredas et al. (1982), the electronic structure of a lithium-doped quaterphenyl anion-radical also differs in a similar quinoidal distortion. With respect to conformational transition, this means less freedom for rotation of the rings in the ion-radicals of quaterphenyl. This effect was also observed for poly-p-phenylene cation-radical (Sun et al. 2007) and anion-radical of quaterphenyl p-quinone whose C—O bonds were screened by o,o-tert-hutyl groups (Nelsen et al. 2007). 

Noll G, Lambert C, Lynch M, Porsch M, Daub J (2008) Electronic structure and properties of poly- and oligoazulenes. J Phys Chem C 112 2156... 

The implementation of the scattering approach and of some simphfied electronic structure models for describing the transport behavior of short poly(dG)-poly(dC) DNA wires [14] have been recently independently proposed within two main classes of models. One involves dephasing [123-125] and the other involves the hybridization of the r-stack [122]. 

Using physical organic chemical rationalizations, we were able to modify the electronic structure of a poly(heterocycle). The result was poly(isothianaphthene) a polymer which is already a semiconductor in the neutral (undoped) state. In the fully doped state, PITN is a transparent conducting polymer. 

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