Self-Assembly of Organic-Inorganic Hybrid Amphiphilic Surfactants with Large Polyoxometalates as Polar Head Groups

Mn-Anderson-C(6) and Mn-Anderson-C(16). A type of inorganic-organic hybrid moleculrs containing a large anionic polyoxometalate (POM) cluster and two C(6) and C(16) alkyl chains, respectively, demonstrate amphiphillic surfactant behaviour in the mixed solvents of acetonitrile and water. The amphiphilic hybrid molecules can slowly assemble into membrane-like vesicles by using the POM clusters as polar head groups, as studied by laser lignt scattering and TEM techniques. The hollow vesicles have a typical bilayer structure with the hydrophilic Mn-Anderson cluster facing outside and long hydrophobic alkyl chains staying inside to form the solvent-phobic layer. Due to the rigidity of the POM polar heads, the two alkyl tails have to bend significantly for the vesicle formation, which makes the vesicle formation more difficult compared to some conventional surfactants. This is the first example of using hydrophillic POM macroions as polar head groups for a surfactant system.