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|Type:||Artigo de periódico|
|Title:||Poly(alkylthiophenes): Chain Conformation And Thermochromism|
|Author:||dos Santos D.A.|
dos Santos M.C.
|Abstract:||The role of conformational disorder in the electronic structure of alkyl-substituted polythiophene is investigated. Thermally-induced twisting of thiophene rings out of the main conjugation plane is assumed. AM1 geometry optimizations were carried out to obtain the molecular torsion potential curves for substituted bithiophenes. Total torsion potentials acting on inter-ring rotations are assumed to come from two contributions, the molecular potential and a phenomenological 'solid state potential' that accounts for inter-chain interactions. It is found that the molecular potential for rotations does not depend on the length of the alkyl group but only on the regiochemistry of substitution. A long, disordered thiophene chain is built to be representative of a classical probability distribution of torsion angles. The electronic structure associated with valence and conduction π bands is calculated within VEH pseudopotential theory and the NFC technique. The dependence of the optical gap on temperature is obtained and is in agreement with experiment. © 1992.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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