Structure and aggregation of lithium dodecylsulfate micellar solutions in the presence of a macrocyclic cage

We study the effects of addition of the macrocyclic cage CESTO (5,12,17-trimethyl-1,5,9,12,17-pentaazabicyclo (7.5.5)nonadecane) on the aggregation behaviour of lithium dodecylsulphate (LDS) in aqueous solution at a pH approximately=12.7. At this pH CESTO is neutral and binds selectively Li counter-ion. Electron spin-echo modulation results show that CESTO interacts with LDS micelles by decreasing the amount of water at the LDS polar headgroups region. Small-angle neutron scattering shows that LDS forms micelles of quasi-spherical shape. Upon addition of CESTO to 1% LDS micellar solution (1/1 mole ratio) we observed a dramatic lowering of the micellar charge, a small growth of the aggregation number, and increased elongation of micelles.