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Master's Dissertation
DOI
https://doi.org/10.11606/D.88.2006.tde-06062007-190120
Document
Author
Full name
Felippe José Pavinatto
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2006
Supervisor
Committee
Oliveira Junior, Osvaldo Novais de (President)
Frollini, Elisabete
Zaniquelli, Maria Elisabete Darbello
Title in Portuguese
Filmes de Langmuir e Langmuir-Blodgett (LB) de azopolímeros com controle do tamanho da cadeia e posição dos cromóforos
Keywords in Portuguese
Armazenamento óptico
ATRP
Azopolímeros
Copolímeros em bloco
Langmuir
Langmuir-Blodgett
Abstract in Portuguese
Azopolímeros apresentam propriedades de fotoisomerização, úteis para confecção de memórias ópticas, que dependem da arquitetura molecular do azopolímero e do filme formado a partir dele. Neste trabalho foram sintetizados polímeros com arquitetura molecular controlada, usando os azomonômeros [4-(N-etil-N-2-(metacriloxietil)) amino-2'-cloro-4'-nitroazobenzeno] (DR13MA) e [4-(N-etil-N-2-(metacriloxietil)) aminoazobenzeno] (MAEAMA). Para a síntese de homopolímeros e copolímeros em bloco foram utilizados dois métodos: NMRP - polimerização radicalar mediada por nitróxidos e ATRP - polimerização radicalar por transferência de átomo. Foram produzidos copolímeros dibloco, com um dos blocos contendo azocorantes, pela reação do monômero DR13MA com macroiniciadores poliestireno (PS) no método NMRP, e poli(metacrilato de metila) (PMMA) via ATRP. Homopolímeros de ambos os azomonômeros foram sintetizados por ATRP, e assim como os copolímeros em bloco mostraram cadeias com baixa polidispersividade. Complementando o trabalho de síntese, foram estudadas as propriedades dos materiais na interface ar-água, utilizando filmes de Langmuir, e procedeu-se a transferência dos mesmos para substratos sólidos formando filmes Langmuir-Blodgett (LB). Nos filmes de Langmuir foi observada a conformação e as interações (agregação) das moléculas dos materiais, destacadamente, no caso do homopolímero HPMAEA, foi observado um patamar próximo a 8 mN/m na isoterma de pressão de superfície, indicando haver reorganização do material no filme. Os filmes LB serviram como objeto de estudo das propriedades ópticas dos compostos, e no caso do homopolímero HPDR13 sintetizado via ATRP, pela primeira vez foi possível a realização de medidas em filmes puros do material. Medidas de armazenamento óptico foram realizadas para comprovar a aplicabilidade dos materiais em memórias ópticas. No caso do terpolímero PS-b-[MMA-co-DR13] sintetizado por NMRP, os resultados de armazenamento foram semelhantes aos obtidos com blendas. Para o homopolímero HPMAEA, uma grande influência do tipo de filme empregado (cast ou LB) foi observada no tempo de escrita das memórias, com o tempo para o filme LB sendo 26 vezes menor. Copolímeros em bloco PMMA-b-DR13 podem ser vantajosos por aliarem as propriedades ópticas do homopolímero HPDR13 à maior estabilidade térmica e mecânica do PMMA.
Title in English
Langmuir and Langmuir-Blodgett (LB) films of azopolymers with controlled chain-length and chromophores position
Keywords in English
ATRP
Azopolymers
Block-copolymers
Langmuir
Langmuir-Blodgett
Optical storage
Abstract in English
Azopolymers display photoisomerization properties, which can be exploited in optical memories, and depend strongly on the molecular architecture of the polymer chain and kind of film employed. In this work, azopolymers with controlled molecular architecture were synthesized using the azomonomers [4-(N-ethyl-N-2(methacryloxyethyl))amino-2'-chloro-4'-nitroazobenzene](DR13MA)and[4-(N-ethyl-N-2-(methacryloxyethyl))aminoazobenzene] (MAEAMA). Two methods were used to synthesize homopolymers and block-copolymers: NMRP - Nitroxide-mediated radical polymerization and ATRP - Atom transfer radical polymerization. Diblock-copolymers were produced, with one block composed by azodyes units, by reacting the monomer DR13MA with a polystyrene (PS) macroinitiator via NMRP, or with poly(methyl methacrylate) (PMMA) macroinitiator via ATRP. Homopolymers of both azomonomers were synthesized by ATRP, and - analogously to the blockcopolymers - exhibited controlled structure with a small polydispersity. The synthesized polymers were then used in the formation of Langmuir films at the air-water interface, which could be transferred onto solid substrates forming Langmuir-Blodgett (LB) films. In Langmuir films, an investigation was made of the conformation and interactions (aggregation) of the film-forming molecules. Interestingly, a plateau was observed at 8 mN/m in the surface pressure isotherm for the HPMAEA homopolymer, pointing to a reorganization of the polymer during compression. For HPDR13 produced by ATRP, it was possible to deposit LB films with no need to use surfactants, unlike the case of HPDR13 synthesized by conventional methods. Optical storage measurements were performed to demonstrate the applicability of the azo-containing materials in optical memories. For the terpolymer PS-b-[MMA-co-DR13] made by NMRP, the storage results were similar to those obtained with blends. In the case of the homopolymer HPMAEA, a large influence of the kind of film used (cast or LB) was observed in the writing time of the memories, with the writing time for the LB film being 26 times faster. PMMA-b-DR13 block-copolymers may be advantageous in combining the optical properties of the homopolymer HPDR13 with the thermal and mechanical stability of PMMA.
 
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FelippePavinatto.pdf (4.98 Mbytes)
Publishing Date
2007-06-11
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
  • PAVINATTO, FJ, et al. Synthesis of azopolymers with controlled structure and photoinduced birefringence in their LB films [doi:10.1016/j.polymer.2008.11.043]. Polymer [online], 2009, vol. 50, n. 2, p. 491-498.
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