Modificação estrutural de triacilgliceróis visando a obtenção de monômeros e polímeros seguindo os princípios da química verde: rotas sintéticas mais eficientes com menor gasto energético
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Data
2022-05-06
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Universidade Estadual Paulista (Unesp)
Resumo
Pesquisas visando a síntese de polímeros utilizando compostos químicos renováveis são cada vez mais frequentes. O óleo vegetal (triacilgliceróis) é um excelente exemplo de composto químico renovável que pode facilmente ser extraído e então modificado para ser aplicado na área de polímeros. Entretanto, apenas a utilização de compostos renováveis já não se faz mais suficiente para uma pesquisa; desta forma, procura-se a utilização de rotas mais eficientes e limpas bem como, um menor gasto energético nos processos de síntese. Para tanto, os 12 princípios da Química Verde podem auxiliar nas pesquisas. Um dos princípios, descreve que os experimentos devem ser feitos se possível em temperatura ambiente para não gerar um gasto energético desnecessário; entretanto muitas reações não ocorrem em temperatura ambiente mesmo com catalisadores apropriados. Faz-se assim necessário a utilização de sistemas que forneçam energia e sejam melhores que as rotas térmicas convencionais; consequentemente, pode-se utilizar sistemas de micro-ondas e reações por luz (fotoquímica). Visando estes aspectos, triacilgliceróis foram quimicamente modificados por irradiação de micro-ondas para a síntese de óleos maleinizados. Estes apresentaram 54% mais incorporação de anidrido na estrutura do que os sintetizados pela rota térmica convencional em apenas 15 minutos de reação. A síntese de monômeros por irradiação de micro-ondas mostrou-se eficiente e limpa quando comparada a rota térmica convencional. Ademais, os óleos maleinizados foram reagidos com dietilenoglicol ou glicerol para obtenção de polímeros que apresentam luminescência sob luz UV, devido ao efeito de emissão induzida por agregação-AIE. A reação foi rápida e não exigiu presença de catalisadores. Triacilgliceróis de baru e macaúba foram epoxidados de maneira eficiente utilizando catalisador heterogêneo (Amberlite IR-120). Estes foram reagidos com CO2 na presença de um catalisador de alumínio para a obtenção de triacilgliceróis carbonatados com conversão ≥99,9. Os triacilgliceróis carbonatados foram reagidos com diaminas para a síntese de polihidróxiuretanos, estes apresentam propriedades de self-healing quando expostas a luz vermelha (660 nm). O triacilglicerol epoxidados de macaúba foram reagidos com ácido acrílico para a síntese de óleos acrilados. O respectivo óleo apresenta autopolimerização sob luz UV sem a necessidade de fotoiniciadores, sendo promissores para a utilização em impressoras 3D. Os materiais poliméricos foram caracterizados por Termogravimetria-Análise Térmica Diferencial Simultânea (TG-DTA) e Calorimetria Exploratória Diferencial (DSC), para a determinação da estabilidade térmica, etapas de degradação e transições vítrea e topológica. As técnicas de espectroscopia vibracional de absorção no infravermelho médio (MIR) e Ressonância Magnética Nuclear (1H-RMN e 13C-RMN) foram utilizados para estudar as modificações estruturais nos óleos vegetais após as reações.
Researches have been improving new polymeric synthetic routes using renewable chemicals. The vegetable oil is an excellent example of a renewable chemical, which can be easily extracted and modified to be applied in the polymer field. However, the use of a renewable chemical is not enough; therefore, researchers have been looking for cleaner and efficient synthetic routes. Thus, the twelve Principles of Green chemistry can assist these researches. One principle describes that experiment should be performed at room temperature not to expend energy; however, some reactions do not occur at room temperature even using correct catalysts. It is therefore necessary to use new efficient energetic systems such as microwave irradiation and light (photochemistry) not to use conventional thermal routes. As consequence, some triacylglycerols were modified by microwave irradiation to synthesize new monomer, which were used in polymers production by photochemistry process. Therefore, triacylglycerols were chemical modified by microwave irradiation to synthesize maleinized oils. These presented 54% more incorporation o anhydride to those synthesized by a conventional thermal route, in only 15 minutes. The synthetic route by microwave irradiation has exhibited a cleaner and more efficient process than the conventional thermal route. Furthermore, maleinized oils were reacted with diethyleneglycol or glycerol to obtain polymers that displays luminescence under UV light, due to the Agreggation-induced Emission-AIE; the reaction was fast without catalyst. Triacylglycerols of baru and macaw were epoxidized in an efficient manner using a heterogeneous catalyst (Amberlite IR-120). Thereafter, these were reacted with CO2 in the presence of an aluminium catalyst to provide carbonated triacyclglycerols with a carbonate conversion of ≥99,9. These carbonated triacyclglycerols were further reacted with diamines to obtain polyhydroxyurethanes, which exhibited self-healing properties under a red light (660 nm). Moreover, the epoxidized triacylglycerol of macaw was reacted with acrylic acid to synthesize acrylated oils. This acrylated oil exhibits self-polymerization under UV light without presence of a coinitiator, which is a promising monomer to be used in 3D printers. All polymeric material were characterized by Simultaneous Thermogravimetry- Differential Thermal Analysis and Differential Scanning Calorimetry to determine their thermal stabilities, degradation steps and glass transition. The techniques such as Mid-Infrared Spectroscopy (MIR) and Nuclear Magnetic Resonance (1H-RMN e 13C-RMN) were used to understand the chemical and structural changes in these vegetable oils.
Researches have been improving new polymeric synthetic routes using renewable chemicals. The vegetable oil is an excellent example of a renewable chemical, which can be easily extracted and modified to be applied in the polymer field. However, the use of a renewable chemical is not enough; therefore, researchers have been looking for cleaner and efficient synthetic routes. Thus, the twelve Principles of Green chemistry can assist these researches. One principle describes that experiment should be performed at room temperature not to expend energy; however, some reactions do not occur at room temperature even using correct catalysts. It is therefore necessary to use new efficient energetic systems such as microwave irradiation and light (photochemistry) not to use conventional thermal routes. As consequence, some triacylglycerols were modified by microwave irradiation to synthesize new monomer, which were used in polymers production by photochemistry process. Therefore, triacylglycerols were chemical modified by microwave irradiation to synthesize maleinized oils. These presented 54% more incorporation o anhydride to those synthesized by a conventional thermal route, in only 15 minutes. The synthetic route by microwave irradiation has exhibited a cleaner and more efficient process than the conventional thermal route. Furthermore, maleinized oils were reacted with diethyleneglycol or glycerol to obtain polymers that displays luminescence under UV light, due to the Agreggation-induced Emission-AIE; the reaction was fast without catalyst. Triacylglycerols of baru and macaw were epoxidized in an efficient manner using a heterogeneous catalyst (Amberlite IR-120). Thereafter, these were reacted with CO2 in the presence of an aluminium catalyst to provide carbonated triacyclglycerols with a carbonate conversion of ≥99,9. These carbonated triacyclglycerols were further reacted with diamines to obtain polyhydroxyurethanes, which exhibited self-healing properties under a red light (660 nm). Moreover, the epoxidized triacylglycerol of macaw was reacted with acrylic acid to synthesize acrylated oils. This acrylated oil exhibits self-polymerization under UV light without presence of a coinitiator, which is a promising monomer to be used in 3D printers. All polymeric material were characterized by Simultaneous Thermogravimetry- Differential Thermal Analysis and Differential Scanning Calorimetry to determine their thermal stabilities, degradation steps and glass transition. The techniques such as Mid-Infrared Spectroscopy (MIR) and Nuclear Magnetic Resonance (1H-RMN e 13C-RMN) were used to understand the chemical and structural changes in these vegetable oils.
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Palavras-chave
Micro-ondas, Fotopolimerização, Química Verde, Modificação química, Polímeros renováveis, Fotoquimica, Microwave, Photopolymerization, Chemical modification, Renewable polymers