High-temperature lamellar of an extremely anti-symmetrical surfactant, barium ethyl(n-octyl)phosphate, in D2O: A small angle neutron scattering study

Abstract

The lamellar structure of an extremely anti-symmetric bi-tail-type surfactant “barium ethyl (n-octyl)phosphate Ba (EOP)2” in D2O was investigated by the SANS method. The SANS intensity spectra were analyzed, based on a one-dimensional paracrystal model with uniaxial randomly oriented stacks. The results provided the lamellar model in which the ethyl and n-octyl chains are closely packed in a tail-to-tail manner which alternately combines the short and long n-alkyl chains. The closely-packed lamella was ascribed to the coordination effect of Ba2+ to the two PO4− groups of the EOP surfactants, as a result of comparison with the x-ray low angle diffraction consequence of “a loosely packed lamellar model” of Li (EOP) (already reported by Hirata et al. [1]).