MICELLAR SOLUTIONS OF OCTYL-18-CROWN-6

The solution properties of the novel surfactant octyl-18-crown-6 (C-8 Phi(6)) have been investigated with phase diagram, light-scattering, a nd surface tension measurements. This tenside is made up of an octyl h ydrophobic chain attached to a 18-crown-6 ether and cyclic polar head- group that is highly selective for complexing Ki ions. The results sho w that C-8 Phi(6) produces micellar structures in water and in KCl aqu eous solutions, with a radius of about 30 Angstrom. Addition of potass ium ions in a molar ratio of 0.4 (KCl/C-8 Phi(6)) increases the hydrop hilicity of the surfactant, as shown by the increment of the phase sep aration temperature, and produces a slight shift in the critical micel lar concentration value, as it results from surface tension measuremen ts. The intermicellar interaction parameter alpha, obtained from QELS experiments, has been discussed. Pure C-8 Phi(6) micelles experience a ttractive intermicellar interactions overimposed to the hard-sphere in teractions, while the K+ complexation of the surfactant polar head-gro ups leads to a decrease of the average attractive component of the int eraction. These results show that intermicellar interactions are selec tively controlled and modulated by simply adding a proper salt that ca n be complexed by the polar head-groups of the surfactant.