Estudo catalítico de fibras poliméricas incorporadas com complexos fotocrômicos de lantanídeos

Abstract

In this study, the synthesis and characterization of coordination complexes of Lanthanides: La, Ce, Eu, Er, Yb and Nd are reported, using the photochromic molecule spiropyran (SPCOOH) as a ligand. The complexes obtained were characterized by absorption spectroscopy in the UV-vis region and vibrational spectroscopy in the infrared region (FTIR), the results indicate that coordination occurs via the merocyanine and carbonyl isomer phenolate of the carboxylic acid group. A kinetic stability study of the merocyanine isomer was performed for all complexes with the acetonitrile solvent. Also, a solvatochromic study of them was carried out in different organic solvents, in which the merocyanine isomer showed different absorptions in the visible region. Through the electrospinning technique, uniaxial fibers were obtained, in which EuMC or ErMC complexes were immobilized on the polycaprolactone (PCL). Both fibers were characterized by the techniques of FTIR, emission electronic spectroscopy, scanning electron microscopy (SEM), measurements of the contact angle of the water with the material surface, and thermal analysis. The results indicate that hydrophobic microfibers were obtained and that the complexes are present in both. The PCL-EuMC fibers were used as a catalyst in the hydrolysis process of the organophosphate bis-2,4 dinitrophenylphosphate, the reaction was monitored by UV-vis and as a result the material achieved a 3-fold increase in the initial speed compared with the uncatalyzed process. Coaxial fibers were obtained using the polymer polymethylmethacrylate (PMMA) on the outside and PCL-EuMC on the inside and the same fiber without the complex. The fibers were characterized by contact angle measurements, in which the fiber-containing complex had a hydrophilic character and without the complex hydrophobic character, beside that the formation of fibers was proved with SEM images. Finally, monoaxial and coaxial fibers were subjected to leaching tests, in which it was observed that in the coaxial fiber the complex did not leach into a buffer solution.