OMRP Fotocontrolada por complexos de Mn (II) coordenados a bases de Schiff não-simétricas e simétricas
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2022-06-28
Autores
Lira, Kathia Hennes
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Universidade Estadual Paulista (Unesp)
Resumo
Em vista da importância e do crescente uso de técnicas de polimerização radicalar controlada, este trabalho propõe a síntese, caracterização e aplicação de complexos de manganês (II) como mediadores deste tipo de reação. Utilizando-se como precursores o 3-terc-butil-salicilaldeído e o 3-etóxi salicilaldeído, obteve-se quatro bases de Schiff, sendo duas delas não-simétricas, Salen-terc-butil e Salen-etóxi e duas simétricas, Salen-di-terc-butil e Salen-di-etóxi, as quais em seguida foram coordenadas ao metal manganês mediante a reação com o cloreto de manganês (MnCl2), obtendo assim os complexos [MnII(Salen-terc-butil)], [MnII(Salen-di-terc-butil)], [MnII(Salen-etóxi)] e [MnII(Salen-di-etóxi)]. Os ligantes de base de Schiff foram caracterizados por RMN, os complexos por Maldi-Tof e ambos por FTIR e UV-Vis. Todos os quatro complexos foram aplicados como mediadores em reações de fotopolimerização radicalar mediada por organometálicos (foto-OMRP) utilizando-se como monômero o acetato de vinila e como iniciador TPO. Os ensaios foram conduzidos em fotorreator a temperatura controlada de 25°C, variando-se as concentrações de monômero e iniciador. A condição que apresentou os melhores resultados de conversão e índice de polidispersidade para cada complexo foi aplicada em um estudo cinético com retirada de alíquotas a cada 10 minutos, deste modo, foi possível uma avaliação da efetividade de cada um dos complexos na mediação das reações de fotopolimerização. Todos os complexos mostraram eficiência na mediação das reações de foto-OMRP.
In view of the importance and increasing use of controlled radical polymerization techniques, this work proposes the synthesis, characterization, and application of manganese (II) complexes as mediators of this type of reaction. Using 3-tert-butyl-salicylaldehyde and 3-ethoxy salicylaldehyde as precursors, four Schiff bases were obtained, two of them non-symmetrical, Salen-tert-butyl and Salen-ethoxy, and two symmetrical, Salen-di-tert-butyl and Salen-di-ethoxy, which were then coordinated to the manganese metal by reaction with manganese chloride (MnCl2), thus obtaining the complexes [MnII(Salen-tert-butyl)], [MnII(Salen-di-tert butyl)], [MnII(Salen-ethoxy)] and [MnII(Salen-di-ethoxy)]. Schiff base ligands were characterized by NMR, complexes by Maldi-Tof and both by FTIR and UV-Vis. All four complexes were applied as mediators in Organometallic Mediated Radical Polymerization reactions (photo-OMRP) using Vinyl Acetate as monomer and TPO as initiator. The tests were conducted in a photoreactor at a controlled temperature of 25°C, varying the concentrations of monomer and initiator. The condition that presented the best results of conversion and polydispersity index for each complex was applied in a kinetic study with withdrawal of aliquots every 10 minutes, in this way, it was possible to evaluate the effectiveness of each of the complexes in the mediation of the reactions of photopolymerization. All complexes showed efficiency in mediating photo-OMRP reactions.
In view of the importance and increasing use of controlled radical polymerization techniques, this work proposes the synthesis, characterization, and application of manganese (II) complexes as mediators of this type of reaction. Using 3-tert-butyl-salicylaldehyde and 3-ethoxy salicylaldehyde as precursors, four Schiff bases were obtained, two of them non-symmetrical, Salen-tert-butyl and Salen-ethoxy, and two symmetrical, Salen-di-tert-butyl and Salen-di-ethoxy, which were then coordinated to the manganese metal by reaction with manganese chloride (MnCl2), thus obtaining the complexes [MnII(Salen-tert-butyl)], [MnII(Salen-di-tert butyl)], [MnII(Salen-ethoxy)] and [MnII(Salen-di-ethoxy)]. Schiff base ligands were characterized by NMR, complexes by Maldi-Tof and both by FTIR and UV-Vis. All four complexes were applied as mediators in Organometallic Mediated Radical Polymerization reactions (photo-OMRP) using Vinyl Acetate as monomer and TPO as initiator. The tests were conducted in a photoreactor at a controlled temperature of 25°C, varying the concentrations of monomer and initiator. The condition that presented the best results of conversion and polydispersity index for each complex was applied in a kinetic study with withdrawal of aliquots every 10 minutes, in this way, it was possible to evaluate the effectiveness of each of the complexes in the mediation of the reactions of photopolymerization. All complexes showed efficiency in mediating photo-OMRP reactions.
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Palavras-chave
OMRP-fotocontrolada, Complexos de manganês (II), Bases de Schiff, Photocontrolled-OMRP, Maganese complexes (II), Schiff bases