Counterion complexation by calixarene ligands in cesium and potassium dodecyl sulfate micelles. A small angle neutron scattering study

Cesium and potassium dodecyl sulfate micellar solutions have been studied i n the presence of three calix[4]arene-crown ethers able to complex cesium a nd potassium micellar counterions in a selective way (C(8)Cal-6 and C(3)Cal -6 for Csi and C(3)Cal-5 for K+). The cesium or potassium dodecyl sulfate m icelles are modeled as two-shell ellipsoids. The surfactant dodecyl chains and part of the calix-crown ligands are located in the micelle hydrophobic core. Intermicellar correlations are calculated according to a multicompone nt primitive model in a mean spherical approximation with a nonadditive dia meter (NARMMSA). We found that calix-crown derivatives addition to cesium d odecyl sulfate micellar solutions leads to a generalized increase of the mi celle aggregation number, a consistent decrease of the micelle ionization, and a micellar grow toward elongated ellipsoids. However, the addition of c alixarene molecules to potassium dodecyl sulfate produces only a slight dec rease of the micellar charge.