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Doctoral Thesis
DOI
https://doi.org/10.11606/T.43.2005.tde-12112013-101015
Document
Author
Full name
Liliana Yolanda Ancalla Dávila
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2005
Supervisor
Committee
Caldas, Marilia Junqueira (President)
Assali, Lucy Vitoria Credidio
Capaz, Rodrigo Barbosa
Chacham, Hélio
Faria, Roberto Mendonça
 
Title in Portuguese
Estudo teórico de formas condensadas de polianilinas
Keywords in Portuguese
Cristalografia física
Estrutura eletrônica
Abstract in Portuguese
Neste trabalho estudamos o efeito de empacotamento, em diferentes formas condensadas, sobre as propriedades estruturais e eletrônicas de um polímero orgânico conjugado, a polianilina, através de simulações teóricas. A metodologia teórica empregada depende do número de átomos nos sistemas escolhidos, e das propriedades investigadas. Assim, para os filmes com milhares de átomos, utilizamos métodos clássicos para a obtenção das propriedades estruturais. Já para o estudo das propriedades eletrônicas, utilizamos métodos quânticos aplicados a sistemas cristalinos. Para estudar as propriedades estruturais em filmes de polianilina, foi necessário parametrizar um campo de força, e escolhemos o UNIVERSAL1.02 (UFF). Os testes iniciais com o novo campo, UFFn, em sistemas cristalinos de polianilina foram promissores, e pudemos obter simulações de filmes realísticos homogêneos, tanto para sistemas reduzidos como oxidados. A densidade obtida para os sistemas poliméricos representam muito bem o valor experimental, e resultados de raios-X e função de distribuição radial são muito semelhantes aos encontrados na literatura. Através do método ab initio SIESTA, estudamos as propriedades estruturais e eletrônicas de sistemas moleculares e cristalinos lD e 3D de polianilina, no estado reduzido e oxidado. Verificamos o efeito de oxidação já para os trímeros de anilina. As interações intra e intercadeias dos sistemas cristalinos são refletidas nas suas propriedades eletrônicas e são analisadas através da estrutura de bandas e densidade de carga. Arranjos diferentes no empacotamento dos cristais revelam um efeito significativo nas propriedades de transporte do material.
 
Title in English
Theoretical study of condensed forms of polyanilines
Keywords in English
Crystallography
Electronic structure
Polymers (organic chemistry)
Abstract in English
In this work we study the effect of packing, in different condensed forms, on the structural and electronic properties of a conjugated organic polymer, polyaniline, through theoretical simulations. The theoretical methodology that we used depends on the number of atoms of the chosen systems and also on the investigated properties. In this way, for films with thousands of atoms we used classical methods, in order to investigate structural properties. For the study of the electronic properties, we used quantum methods applied to crystalline systems. For the study of the structural properties of polyaniline films, it was necessary to parameterize a force field, and we chose the UNIVERSAL1.02 (UFF) field. The initial tests with the new field, UFFn, in crystalline films of polyaniline were successful, and we were able to obtain simulations of realistic homogeneous films for both reduced and oxidized systems. The density obtained for polymeric systems represents well the experimental value, and results of X-rays as a function of the radial distribution are very similar to those found in literature. By means of the ab initio SIESTA method, we studied the structural and electronic properties of molecular and lD and 3D crystalline systems of polyaniline, in the reduced and oxidized states. We verified the oxidation effect already for trimers of aniline. The inter-chain and intra-chain interactions of the crystalline systems are reflected in their electronic properties and were analyzed through the band structure and charge density. Different arrangements in the packing of the crystals reveal a significative effect in the transport properties of the material
 
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RE47444Davila.pdf (91.47 Mbytes)
Publishing Date
2013-12-17
 
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