Micellar properties of zwitterionic phosphobetaine amphiphiles in aqueous solution: Influence of the intercharge distance |
| |
Authors: | Y. Chevalier L. Germanaud P. Le Perchec |
| |
Affiliation: | (1) Present address: Laboratoire des Matériaux Organiques, CNRS, BP 24, Vernaison, France;(2) Centre de Recherche Elf Solaise, Saint Symphorien d'Ozon, BP 22, France |
| |
Abstract: | Zwitterionic amphiphiles of the general formula H(CH2)y+ N(CH3)2(CH2)n PO2C6H5–, where the number of intercharge methylenesn is varied, were studied in dilute aqueous solution. Their critical micellar concentrations show a peculiar variation withn, first increasing asn varies from 1 to 4 and then slowly decreasing as methylenes are added up to 10. This behavior is interpreted as being the consequence of two opposite contributions. The first is the classical CMC lowering due to the increase of hydrophobic character with the total number of methylene groups in the surfactant molecule. The second contribution is the increase in the dipole moment of the zwitterionic headgroup withn, leading to stronger dipole-dipole repulsions between headgroups at the micellar surface. Experimental results suggest that the dipole moment does not increase linearly withn because of the polymethylene chain flexibility. This is supported by13C NMR relaxation experiments. |
| |
Keywords: | Zwitterionicamphiphiles phenylphosphinatobetaines micelles 13CNMR relaxation |
本文献已被 SpringerLink 等数据库收录! |
|