Efeito dos ânions de líquidos iônicos dicatiônicos na formação de agregados em solução

Detalhes bibliográficos
Ano de defesa: 2014
Autor(a) principal: Bender, Caroline Raquel
Orientador(a): Não Informado pela instituição
Banca de defesa: Não Informado pela instituição
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.