SÍNTESE E CARACTERIZAÇÃO DE NOVOS SURFACTANTES NÃO-IÔNICOS PARA CATÁLISE MICELAR: NANORREATORES A PARTIR DO CARDANOL E GLICEROL

Abstract

From raw materials from renewable sources derived from Brazilian biomass, cardanol and glycerol, pegylated amphiphilic compounds (compounds 3 and 4, respectively) and a gemini surfactant (5) were synthesized, which were characterized by nuclear magnetic resonance spectrometry (1H and 13C NMR), Infrared (IR) spectroscopy and Mass spectrometry. Solutions of varying concentrations from 3,35 x1 0-3 to 4,25 x 10-11 mol L-1 were prepared and measurements of dynamic light scattering (DLS) werw performed, Fluorescence, Infrared and Polydispersity (PDI) were performed. Then it was possible to obtain the critical micellar concentration (CMC) of the compounds. Therefore, the critical micellar concentration of surfactant 4, in the value of 8 ± 5 ˣ 10-10 mol L-1, was determined by the dynamic light scattering technique and by pyrene fluorescence. It was not possible to obtain the respective critical micellar concentrations of surfactants 3 and 5 by the same techniques. Through the dynamic light scattering technique, the hydrodynamic diameter (Dh) of the micelles was determined, as well as the respective polydispersity of each surfactant, in different concentrations. Surfactant 3 supplied micelles in water with average micellar sizes around 320 nm, at the various dilutions and temperatures studied. At a temperature of 45 °C and at a concentration of 2.9 ˣ 10-5 mol L-1, however, it presented sizes of 73.35 nm, with moderate polydispersity. The surfactant gemini 5 supplied micelles in water in sizes suitable for nanoreactors in the range of 51.45 to 106.0 nm, at a concentration of 1.86 ˣ 10-5 mol L-1 and at temperatures of 10, 15, 25 and 35 °C. Sizes of 94.6 and 80.6 nm were observed for the molar concentration of 1.86 ˣ 10-8 mol L-1 at temperatures of 10 and 15 °C, respectively. In the other dilutions and temperatures, the sizes of the micelles were above the range of 115 to 645 nm. Surfactant 4 provided micelles with ideal sizes for micellar catalysis. Particularly, at room temperature (25 °C) micelles in the range of 38.97 - 86.92 nm are formed in different concentrations. At a concentration of 3.35 ˣ 10-3 mol L-1, the hydrodynamic radius was 86.92 nm and the polydispersity <0.2, indicating a monodispersed and stable micellar system. These results suggest that the three surfactants, with emphasis on compound 4, can form micelles with appropriate sizes to function as nanoreactors in clean and environmentally correct organic synthesis. Preliminarily, the surfactant 3 was tested in Morita-Baylis-Hillman (MBH) reaction. 14 Aromatic aldehydes (6a-m) were used to react with n-butyl acrylate (7). The yields of MBH 8a-m adducts were between 50-97%, which shows that this surfactant promotes the expected micellar catalysis, with an effect on accelerating the speed of this reaction compared to surfactants already known as SDS and TPGS-750-M.