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Doctoral Thesis
DOI
10.11606/T.88.2009.tde-18032009-101119
Document
Author
Full name
Daniel Souza Corrêa
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2009
Supervisor
Committee
Mendonça, Cleber Renato (President)
Cavalheiro, Carla Cristina Schmitt
Frateschi, Newton Cesario
Li, Maximo Siu
Zucolotto, Valtencir
Title in Portuguese
Absorção de multi-fótons em polímeros e resinas poliméricas: espectroscopia não linear e microfabricação
Keywords in Portuguese
Absorção de dois fótons
espectroscopia não linear
fotopolimerização
Microfabricação
Multi-fótons
resinas dopadas
Técnica de varredura-Z
Abstract in Portuguese
Nesta tese, estudamos o processo de absorção multifotônica em polímeros e resinas poliméricas, abordando tanto aspectos fundamentais quanto aplicados. Com relação aos aspectos fundamentais, estudamos processos de absorção multifotônica (absorção de dois, três e quatro fótons) no polímero conjugado MEH-PPV (poly(2-methoxy-5-(2´-ethylhexyloxy)-1,4- phenylenevinylene)), utilizando a técnica de Varredura-Z com pulsos ultracurtos. Através desta técnica, determinamos o espectro da absorção de dois, três e quatro fótons do MEHPPV. As seções de choque de absorção de multi-fótons correspondentes a cada processo foram determinadas através do ajuste das curvas experimentais com um conjunto de equações desenvolvidas neste trabalho. Os resultados obtidos permitiram traçar relações entre os espectros não lineares e os níveis de energia do polímero. Na vertente mais aplicada do projeto, estudamos a fotopolimerização de resinas acrílicas através do processo de absorção de dois fótons. Devido ao confinamento espacial da polimerização, graças à absorção de dois fótons, este método permite a confecção de micro-estruturas complexas para diversas aplicações tecnológicas. Além da fabricação de microestruturas convencionais não dopadas, neste trabalho desenvolvemos uma metodologia que possibilita a fabricação de microestruturas dopadas com MEH-PPV, visando a produção de micro-elementos fluorescentes para dispositivos fotônicos, e microestruturas dopadas com quitosana, um polímero biocompatível que pode ser utilizado em aplicações médicas e biológicas.
Title in English
Multi-photon absorption in polymers and polymeric resins: nonlinear spectroscopy and microfabrication
Keywords in English
Doped resins
microfabrication
Multi-photons
nonlinear spectroscopy
photopolymerization
Two-photon absorption
Z-scan technique
Abstract in English
In this thesis we have studied the multi-photon absorption process in polymers and polymeric resins, exploiting its fundamental as well as technological aspects. Regarding the fundamental aspects, we have studied the multi-photon absorption (two-, three- and four-photon absorption) in the conjugated polymer MEH-PPV (poly(2-methoxy-5-(2´-ethylhexyloxy)-1,4-phenylenevinylene)), by using the Z-scan technique with ultrashort laser pulses. Through this technique, we determined the two-, three- and four-photon absorption spectra of MEH-PPV. The multi-photon absorption cross-sections, corresponding to each specific process, have been determined by fitting the experimental data with a set of equations developed in this work. The results allowed us to correlate the nonlinear absorption spectra to the energy level of the polymer. On the technological side of this thesis, we have investigated the photopolymerization of acrylic resins by two-photon absorption. Because of the spatial confinement of the polymerization, resulting from the two-photon excitation, this method allows the fabrication of complex microstructures which can be used for several technological applications. In addition to the fabrication of undoped microstructures, in this work we have developed a methodology that allows the fabrication of microstructures doped with MEHPPV, aiming the production of fluorescent micro-elements for photonics applications, and microstructures doped with chitosan, a biocompatible polymer, that can be used for medical and biological applications.
 
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Publishing Date
2009-03-23
 
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