Estudo e transformação química de biopolímeros a base de quitina e quitosana para preparação de materiais com diversas propriedades
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Data
2012-08-21
Autores
Pereira, Fernanda Stuani [UNESP]
Título da Revista
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O presente trabalho descreve modificações estruturais feitas na cadeia lateral do polímero quitina-quitosana mediante a N-alquilação com um aldeído aromático, a qual origina a base de Schiff como produto intermediário, seguido de uma redução com cianoborohidreto de sódio (NaBH3CN) para a formação do composto N-Benzilquitosana. Subsequentemente, reações de acoplamento entre o produto sintetizado e diferentes sais de diazônio foram realizadas para produzir uma nova classe de compostos poli-azóicos a partir deste polímero. Estas modificações são importantes pela síntese de novos derivados com potencial aplicação como materiais orgânicos. Pela técnica de ressonância magnética nuclear de próton em solução, determinou-se o grau de desacetilação do polímero que foi de 68 %. O grau de substituição do derivado N-Benzilquitosana também foi determinado por RMN de 1H e o valor encontrado foi de 46 %. Todos os compostos foram caracterizados por espectroscopia de absorção na região do infravermelho e ressonância magnética nuclear em solução e no estado sólido, que confirmaram a síntese dos derivados poliméricos. Devido ao alto peso molecular do polímero e seus derivados, estes foram hidrolisados e os oligômeros formados foram estudados por espectrometria de massas com ionização por eletrospray. Além de confirmar a formação do composto N-Benzilquitosana, constatou-se uma reação de substituição nucleofílica aromática do átomo de bromo e do grupo nitro pelo átomo de cloro promovido pela alta concentração de íons cloretos no meio reacional. Entretanto, a técnica não se mostrou adequada para a caracterização dos poli-azo-compostos, pois a reação de hidrólise ácida leva a uma degradação dos mesmos. A espectroscopia de UV-VIS permitiu identificar as bandas de absorção dos...
The present work describes the structural modifications made in the side chain of the polymer chitin-chitosan by N-alkylation with an aromatic aldehyde, which forms the Schiff base as an intermediate, followed by reduction with sodium cyanoborohydride (NaBH3CN) to form the N-Benzyl chitosan compound. Subsequently, coupling reactions between the synthesized product and different diazonium salts were made to produce a new class of poly-azo-compounds from this polymer. These changes are important for the synthesis of new derivatives with potential use as organic materials. By proton nuclear magnetic resonance, it was determined the degree of deacetylation of the polymer, which was 68%. The degree of substitution of N-Benzyl chitosan derivative was also determined by 1H NMR and the value was 48%. All compounds were characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance, which confirmed the synthesis of polymeric derivatives. Due to the high polymer molecular weight and its derivatives, they were hydrolysed and the oligomers formed were analyzed by mass spectrometry with electrospray ionization. In addition to confirm the formation of the compound N-Benzyl chitosan, there was a nucleophilic aromatic substitution reaction of the bromine atom and the nitro group by chlorine atom promoted by high concentration of chloride ions in the reaction medium. However, the technique was not suitable for the characterization of poly-azo-compounds because the reaction of acid hydrolysis leads to their degradation. The UV-VIS spectroscopy allowed the identification of the absorption bands of poly-azo-compounds and showed that the substituents influence the absorption causing an batocromic effect to a longer wavelength. Finally, it was studied the thermal behavior of the polymer chitin-chitosan and its derivatives by thermogravimetry... (Complete abstract click electronic access below)
The present work describes the structural modifications made in the side chain of the polymer chitin-chitosan by N-alkylation with an aromatic aldehyde, which forms the Schiff base as an intermediate, followed by reduction with sodium cyanoborohydride (NaBH3CN) to form the N-Benzyl chitosan compound. Subsequently, coupling reactions between the synthesized product and different diazonium salts were made to produce a new class of poly-azo-compounds from this polymer. These changes are important for the synthesis of new derivatives with potential use as organic materials. By proton nuclear magnetic resonance, it was determined the degree of deacetylation of the polymer, which was 68%. The degree of substitution of N-Benzyl chitosan derivative was also determined by 1H NMR and the value was 48%. All compounds were characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance, which confirmed the synthesis of polymeric derivatives. Due to the high polymer molecular weight and its derivatives, they were hydrolysed and the oligomers formed were analyzed by mass spectrometry with electrospray ionization. In addition to confirm the formation of the compound N-Benzyl chitosan, there was a nucleophilic aromatic substitution reaction of the bromine atom and the nitro group by chlorine atom promoted by high concentration of chloride ions in the reaction medium. However, the technique was not suitable for the characterization of poly-azo-compounds because the reaction of acid hydrolysis leads to their degradation. The UV-VIS spectroscopy allowed the identification of the absorption bands of poly-azo-compounds and showed that the substituents influence the absorption causing an batocromic effect to a longer wavelength. Finally, it was studied the thermal behavior of the polymer chitin-chitosan and its derivatives by thermogravimetry... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Materiais, Ciência dos materiais, Quimica organica, Quitina, Biopolimeros
Como citar
PEREIRA, Fernanda Stuani. Estudo e transformação química de biopolímeros a base de quitina e quitosana para preparação de materiais com diversas propriedades. 2012. x, 95 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Ciências e Tecnologia, 2012.