SANS and SAXS study on aqueous mixtures of fullerene-based star ionomers and sodium dodecyl sulfate

Fullerene-based star ionomer C60[CO(CH2)5O(CH2)4SO3Na]6 (FC10S), with six sodium-dodecyl-sulfate-like arms randomly bonded on the fullerene, has been synthesized. This novel molecule has a high water solubility and a structural shape resembling the skeleton of a micelle of sodium dodecyl sulfate (SDS). We study aqueous mixtures of the C60-based ionomers and SDS using small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS). With a selected deuteration of SDS, we have identified the formation of complex aggregates of FC10S with SDS in the mixtures. The structural information of the complex aggregates is extracted from the SANS and SAXS data measured for the mixtures. On the average, the complex aggregates observed have a cylinder-like shape with a radius of 19 Å and a length of ≈100 Å for the sample mixtures containing 2.3 or 1.2 mM of FC10S and 6 mM of SDS. The mean aggregation numbers of FC10S and SDS in each complex aggregate are 15 and 11, respectively.