Estudo das propriedades eletrônicas da polianilina por cálculos de primeiros princípios

Abstract

For a long time it was believed that polymers were materials which didn't have any conductive properties associated to them. However, several studies has been made through the years to show the birth of a new class of polymeric materials, known as intrinsically conductive polymers. This class of polymers generally consist of chains having a conjugation structure, with alternating double and single bonds of carbon atoms. This combination allows electronic transport through the polyaniline structure. Since polyaniline represents a many-particle system, we present an introduction to the Schrodinger equation, the Thomas-Fermi theory, an to the Khon-Sham equations, which are important to understand the methods used, in order to calculate the electronic transport properties of doped polyaniline with different chloride contents. To calculate the electronic structure and electronic transport properties, we used the first principles, also known as textit ab-initio method , by the density functional theory technique (DFT). The electronic properties of polyaniline were studied through the bands diagram, density of states per atom and orbital, charge density, transmittance and electrical current for each state of oxidation/reduction of this conjugated polymer. The results obtained show a good qualitatively agreement with the experimental results. It was possible to observe the transition process of polyanilines, affording to obtain the semiconductor and insulating phases, as shown in the bands diagrams and electric current spectra.