Estudo dos ions benzenossulfonato, benzoato e anilinio em soluções micelares atraves dos tempos de relaxação de 13C de ressonacia magnetica nuclear

AUTOR(ES)
DATA DE PUBLICAÇÃO

1990

RESUMO

Carbon-13 spin-lattice relaxation times were used to characterize the behavior of ionic solutes in isotropic micellar solutions. Threee monosubstituted benzene were analyzed, benzenesulfonate, benzoate and anilinium ions, in micellar solutions prepared using the surfactants alkyltrimetylammonium bromide (C10, C14 and C16), decylammonium chloride, potassium dodecanoate, sodium decylsulfate and some mixtures of them surfactants. The solute was introduced as simple salts or as the counterion of the surfactant. The effect of decanol was investigated in solutions prepared using ionic surfactants sodium decylsulfate and potassium dodecanoate. The ratio of the 13 C spin-lattice relaxation times of the ortho and meta carbons to that of the para carbon (T1 om/ T1 p) was used to characterize the anisotropy of the rotational diffusion of solute. The T1 data for the benzenesulfonate ion in micellar solutions of anionic surfactants indicate that the ratio is large because of a highly anisotropic rotational difusion due a strong solute-micelle interaction. It was concluded that the benzenesulfonate ion is solubilizated with the aromatic part in the micelle. In the cationic systems, the ratio T1 om / T1 p is comparable to that in non-micellar aqueous solutions. It was concluded that the benzenesulfonate ion is predominantly in the aqueous region of the micellar interface. The dynamic behavior of benzoate ion was similar to that observed for the benzenesulfonate ion. However, it was observed that the ratio T1 om/ T1 p depend on partition of the solute between the aqueous region and micellar fase. In the micellar solutions using sodium decylsulfate surfactant, the anisotropy of the rotational difusion of the anilinium ion was greater than that in non-micellar aqueous solution indicating a solute-micelle interaction. These results were analysed together with the degree of order, determined in nematic mesophases, which describe the partial orientation of the solute. The data indicate that the anilinium ion is incorporated in micella. In the cationic micellar systems, the results indicate a distribution of anilinium ion between the aqueous region and micellar fase, which was sensitive to the nature of the surfactant headgroups.

ASSUNTO(S)

ions solução (quimica) ressonancia magnetica nuclear

ACESSO AO ARTIGO

Documentos Relacionados