Preparação e caracterização de compósitos conjugados fotocrômicos e luminescentes para aplicação em sensores de radiação
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Data
2018
Autores
Menandro, Alessandra Stacchini [UNIFESP]
Orientadores
Péres, Laura Oliveira [UNIFESP]
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
O desenvolvimento de novos materiais para o uso em dosímetros de radiação vem crescendo
e se tornando de grande importância para aplicações em diversas áreas. Moléculas fotocrômicas são
alvo de estudos recentes devido ao fato de seus espectros serem alterados, de forma reversível,
quando expostas à uma radiação. Já os polímeros conjugados apresentam propriedades luminescentes
que os tornam de grande potencial tecnológico para aplicação em dosímetros. A combinação de
moléculas fotocrômicas e polímeros conjugados, formando-se compósitos, possibilita a formação de
novos materiais fotorreceptivos com propriedades únicas. A eficiência destes novos materiais é
devida a processos fotofísicos de transferência de energia, cujo estudo é de grande importância para
um melhor entendimento das características do compósito formado. Quando em solução, os
diferentes solventes podem alterar o empacotamento e a orientação das moléculas, fatores estes que
são essenciais para a eficiência do sistema a ser formado. Dessa forma, foi utilizado como polímero
conjugado o poli(3-hexiltiofeno-co-1,4-fenileno), sintetizado pela rota de Suzuki, e como molécula
fotocrômica o 4-aminoazobenzeno, que foi sintetizado por meio do acoplamento do sal de diazônio.
Cada material foi devidamente caracterizado estrutural e eletronicamente. Os compósitos foram
formados em solução, utilizando-se diferentes solventes para avaliar a sua influência e determinar
parâmetros importantes que caracterizam os sistemas por meio da teoria de Föster. Estes foram
analisados por espectroscopia eletrônica. Após o estudo aprofundado a respeito de cada sistema,
determinou-se que para estes compósitos formados em solução, o etanol como solvente se mostrou
formar um sistema com maior eficiência de transferência de energia, o que pode ser comprovado por
meio dos valores obtidos dos parâmetros calculados, como o do raio crítico de Föster. Além disso, o
estudo químico quântico computacional realizado neste trabalho permitiu avaliar e fazer proposições
sobre como se dá a interação entre as moléculas investigadas, se mostrando de grande importância
para o entendimento dos compósitos formados e dos processos fotofísicos que nestes ocorrem.
The development of new materials to use in radiation dosimeters has been growing and becoming important for applications in several areas. The photochromic molecules have been used for several applications due to the reversible change of the spectra, induced for an electromagnetic radiation. The great attention in conjugated polymers and their application in dosimeters is related to their luminescent properties. The combination of conjugated polymers and photochromic molecules can be result in a composite, that can has new photoresponsive materials with unique properties. The efficiency of these materials is due to the photophysics process of energy transfer, which becomes a study of great importance to understand the characteristics of the new material. In solution, the use of different solvents can be change the packing and the orientation, which are essential for the efficiency of the system to be formed. In this way, for this work, the conjugated polymer poly(3-hexylthiophene-co-1,4-phenilene) was synthesized by Suzuki route, and photochromic molecule 4-aminoazobenzene was synthesized by diazonium salt coupling. Both were characterized structurally and electronically. The composites were formed in solution, using different solvents to evaluate their influence and determine essential parameters that characterize the systems through Föster's theory. The composite was analyzed by electronic spectroscopy. After the detailed study about each system, it was determined that the ethanol is the better solvent for a system with greater energy transfer efficiency, which can be proven from the parameters calculated, such as the Föster's critical radius. In addition, a computational quantum chemical study was carry out, which was possible to evaluate and suppose the interactions between the both investigated molecules, shown to be important to understand the composites formed and the photophysical processes that occur.
The development of new materials to use in radiation dosimeters has been growing and becoming important for applications in several areas. The photochromic molecules have been used for several applications due to the reversible change of the spectra, induced for an electromagnetic radiation. The great attention in conjugated polymers and their application in dosimeters is related to their luminescent properties. The combination of conjugated polymers and photochromic molecules can be result in a composite, that can has new photoresponsive materials with unique properties. The efficiency of these materials is due to the photophysics process of energy transfer, which becomes a study of great importance to understand the characteristics of the new material. In solution, the use of different solvents can be change the packing and the orientation, which are essential for the efficiency of the system to be formed. In this way, for this work, the conjugated polymer poly(3-hexylthiophene-co-1,4-phenilene) was synthesized by Suzuki route, and photochromic molecule 4-aminoazobenzene was synthesized by diazonium salt coupling. Both were characterized structurally and electronically. The composites were formed in solution, using different solvents to evaluate their influence and determine essential parameters that characterize the systems through Föster's theory. The composite was analyzed by electronic spectroscopy. After the detailed study about each system, it was determined that the ethanol is the better solvent for a system with greater energy transfer efficiency, which can be proven from the parameters calculated, such as the Föster's critical radius. In addition, a computational quantum chemical study was carry out, which was possible to evaluate and suppose the interactions between the both investigated molecules, shown to be important to understand the composites formed and the photophysical processes that occur.