Síntese e propriedades de novos líquidos iônicos derivados de ânions carboxilados e interações com a metilcelulose para aplicações em alimentos

Abstract

This work presents the synthesis, characterization and study of the aggregation properties of monocationic ionic liquids (ILs) with anions derived from carboxylic acids (butanoic, crotonic and pentanoic) in aqueous solution, as well as studies of aggregation and gelation properties of IL/methylcellulose (MC) systems. The characterization of ILs was performed by ¹H and ¹³C Nuclear Magnetic Resonance (NMR), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The results showed that [C₁₀MIM][CRO] was more thermally stable, with a decomposition temperature close to 245 °C. The [C₁₀MIM][BUT] and [C₁₀MIM][CRO] had behavior of predominantly crystalline structures in the evaluated temperature range. The [C₁₀MIM][PENT] underwent amorphization after the first heating/cooling cycle. Aggregation studies were performed by Electrical Conductivity, ¹H NMR, DSC and UV-Visible Spectrophotometry. The results showed that the IL/MC aggregation process is thermodynamically favored. The NMR data showed that the ¹H nuclei of [C₁₀MIM][PEN] and [C₁₀MIM][CRO] showed a deshielding effect in the presence of MC. On the other hand, [C₁₀MIM][BUT] demonstrated two behaviors – deshielding of H2 and other H bound to the cationic head (with the exception of H4) and shielding of the hydrogens of the alkyl chain and of the anions – indicating differences in the intermolecular interactions with MC . Data from the gelation study showed that the addition of [C₁₀MIM][BUT] and [C₁₀MIM][CRO] increases the sol-gel transition temperature of the MC in water.