Avaliação da atividade catalítica de novos complexos à base de Co(II), Mn(II) e Fe(II) para polimerização oxidativa

Abstract

The main aim of this study was to develop new catalysts for the oxidative polymerization of vegetable oils, and may be applied in the coatings industry, in order to control the cure process oil resins, without compromising the final quality of the material. This study was conducted in two parts. At first, the nitrogen-based ligands 2,2'-bipyridyl, 4,4'-dimethyl-2,2'-bipyridyl, 6,6'-dimethyl-2,2'-bipyridyl, 1,10- phenanthroline, 4-methyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline were coordinated to the metal center of the catalyst precursor, producing new complexes based on cobalt, manganese and iron. The right ratio of ligands attached at the metal center was determined by ultraviolet spectroscopy, and adopted during the oxidative polymerization reactions of linseed oil in order to evaluate catalytic properties by the evolution of the viscosity of the reaction medium. Additionally, infrared spectroscopy was used to verify the evolution of some chemical groups during the polymerization process. It was possible to observe that the manganese and iron catalytic systems, modified by the presence of the nitrogen-based ligands, were more efficient than those of based on cobalt. The addition of 5,6-dimethyl-1,10-phenanthroline in the reaction mixture led to better results in terms of increase of the viscosity rate, probably due to electronic effects, or due the compatibility of the catalyst-substrate. The adoption of nitrogen-based ligands in the reaction medium, in order to accelerate the oxidative polymerization process is very promising.