Um estudo da interação entre ions aromaticos e micelas, em cristais liquidos liotropicos nematicos e em soluções isotropicas, por ressonancia magnetica nuclear

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

The interaction between ions and the electric double layer of micelles and biological membranes depends on a balance between the electrostatic torces and the hydrophobic effect. In this work, the interaction of the ions anilinium, benzoate, p-toluenesulfonate and benzenesulfonate with micelles was studied in nematic Iyotropic liquid crystals and isotropic solutions. Cationic and anionic surfactants were employed in these systems. The partial orientation of each aromatic ion in nematic Iyotropic mesophases was measured trom the hydrogen and deuterium nuclear magnetic resonance (NMR) spectra. Translational diffusion of the aromatic ions and micelles in isotropic solutions were measured by the NMR pulsed field gradient spin-echo technique called DOSY. A two site model was assumed and the partition ot ions in solution was determined trom the diffusion data. The rotational diffusion anisotropy of the perdeuterated aromatic ions was studied in the nematic Iyotropic mesophase and in the non-micellar solutions, using the ratio of the relaxation times T1 of the aromatic deuterium : a =T1(orto,meta) / T1(para). All measurements were made at 300K. The results showed that the electrostatic interactions have a strong influence on the orientation of the aromatic ions. In cases where the electrostatic interactions between the aromatic ions and the micelle interface were favourable, the results indicated that more than 90% of the ions were associated with the micelles. In cases where the electrostatic interactions were not favourable, there is an incorporation of the aromatic ring of the ion in the micelle due to the hydrophobic effect.

ASSUNTO(S)

quimica analitica cromatografia de gas

ACESSO AO ARTIGO

Documentos Relacionados