SANS and SAXS Studies on the Aggregates Properties of A Gemini-Type Amphiphilic Dendrimer in Solution

By combined use of time-of-flight small-angle neutron scattering (SANS) and synchrotron radiation small-angle X-ray scattering (SAXS), we investigated aggregation behaviors of gemini-type amphiphilic dendrimers (2C12-2denGn, where n denotes the generation number) in an aqueous solution with varying generation (n). 2C12-2denGn consists of two poly(amidoamine) (PAMAM) dendrons and C12 hydrocarbon chains connected by spacer chains. We found that the radius of gyration (Rg) evaluated from the SANS profiles for the 2C12-2denGn solution was nearly constant with n, which was remarkably different from that of dendrimer particles. In addition, model-fitting analysis for the SANS and the SAXS results was carried out using a theoretical scattering function of the polydisperse core-shell sphere model. With increasing n, the core radius gradually decreased, whereas the shell thickness increased. Although the hydrophilic dendron portion was much balky, the results suggested that 2C12-2denGn formed small spherical micelles with an overall radius of about 31 A. This is due to efficient arrangements of both dendrons and hydrocarbon chains in an aqueous solution.