Efeito dos ânions de líquidos iônicos dicatiônicos na formação de agregados em solução
Ano de defesa: | 2014 |
---|---|
Autor(a) principal: | |
Orientador(a): | |
Banca de defesa: | |
Tipo de documento: | Dissertação |
Tipo de acesso: | Acesso aberto |
Idioma: | por |
Instituição de defesa: |
Universidade Federal de Santa Maria
BR Química UFSM Programa de Pós-Graduação em Química |
Programa de Pós-Graduação: |
Não Informado pela instituição
|
Departamento: |
Não Informado pela instituição
|
País: |
Não Informado pela instituição
|
Palavras-chave em Português: | |
Link de acesso: | http://repositorio.ufsm.br/handle/1/10584 |
Resumo: | This work reports the study of the molecular structure influence of ionic liquid (IL) derived from 1,8-bis(3-methylimidazolium-1-yl)octane in the aggregates formation in a solution ethanol in water (4,75%) and in ethanol (95%). Was varied the anions (Br-, NO3-, BF4-, SCN- e NTf2-) of IL and the aggregation behavior was investigated by various methods, such as differential scanning calorimetry (DSC), conductivity, surface tension, fluorescence and dynamic light scattering (DLS). In the ethanol in water solution (4,75%), the critical aggregation concentration values (cac) (114 to 205 mM), free energy of aggregation (ΔG°a) ( 15 to 18 kJ/mol) and ionization degree (α) (0,37 a 0,44) for the IL with Br-, NO3-, BF4-, SCN- significantly decreased with the increase of anion hydrophobicity. In ethanol, the cac values (165 to 500 mM) and ΔG°a ( 9 to 11 kJ/mol) also decreased with the increase of anion size and hydrophobicity. The free energy adsorption data (ΔG°ads) (-35 to -39 kJ/mol) demonstrated that the ILs, in general, have a good surfactant activity and this property improve with the decrease in the hydrophobic characteristics of anions. In general, in the solvents used in this study, the hydrodynamic radius (Rh) of aggregates ranged between 200 and 500 nm for all the ILs. The critical packing parameter was determined using data from the X-Ray (of IL 4) and surface tension, and showed that aggregates are micelar. The cac data was obtained by the techniques of conductivity, fluorescence and surface tension. Where, was observed that increasing the anion hydrophobicity of dicationic ILs structure favored the formation of aggregates, while less hydrophobic anions improved the surfactant properties of the IL structures. |