Molecular association of cryptand 221D in NaCl-water solutions. A small-angle neutron scattering study

Abstract
Molecules of 5-Decyl-4,7,13,16,21-pentaoxa-1,10-diaza-bicyclo-[8.8.5.]tricosan (221D) and its sodium complex, with both a hydrophobic and a hydrophilic portion, are expected to form aggregates in water solutions. This was confirmed by surface tension measurements. The aggregation behaviour was studied by small-angle neutron scattering at two different [NaCl]/[221D] molar ratios, such as to obtain, in one case, aggregates entirely made up of ionic monomers, and in the other, mixed micelles constituted by both ionic and non-ionic units. The variation of the aggregation number and number of aggregates indicated that, in the former case, smaller micelles were formed, as a consequence of repulsion among the ionic head groups.