Reverse-vesicle formation of organic-inorganic polyoxometalate-containing hybrid surfactants with tunable sizes.

The formation of reverse-vesicular structures of the polyoxometalate-containing hybrid surfactants [nBu(4)N](3)[MnMo(6)O(18){(OCH(2))(3)-CNHCO(CH(2))(n-2)CH(3)}(2)] (Mn-Anderson-C(n), n=6, 16) in nonpolar medium was achieved by titrating toluene into Mn-Anderson-C(n)/acetonitrile (MeCN) solution. Stepwise change of the solvent polarity induces self-association of the hydrophilic Mn-Anderson cluster on the hybrid amphiphiles. The reverse-vesicle formation was characterized by laser light scattering and further confirmed by transmission electron microscopy techniques, and the vesicle sizes increase with increasing toluene contents. The assembly process was accelerated at an elevated temperature. The length of the alkyl tails on the hybrid surfactants has a minor effect on the vesicle sizes, because the strong attraction between the polyoxometalate clusters is more dominant in the reverse-vesicle formation.