Syntheses and phase-transfer properties of dendritic nanocarriers that contain perfluorinated shell structures.
Perfect dendrimers that contain perfluorinated shells have recently attracted attention because they have been shown to encapsulate polar molecules in supercritical CO(2) and catalytically active metal nanoparticles in perfluorinated solvents. Moreover, they can then be easily separated after reaction from the biphasic organic/fluorous system. In this paper several dendritic architectures that contain perfluorinated shells were derived by covalent modification of glycerol dendrimers ([G0.5]-[G3.5]), hyperbranched polyglycerol, and polyethyleneimine. These core-shell architectures show interesting physicochemical properties. For example, they are soluble in fluorinated solvents, they are able to transport different guest molecules, and they display thermomorphic behavior. The transport capacity of these molecular nanocarriers increases significantly when amino groups are present in the core. Certain functionalized polyethyleneimines that contain perfluorinated shells show high transport capacities (up to 3 dye molecules per nanocarrier) in perfluorinated solvents. Moreover, these perfluoro-functionalized dendritic polyethyleneimines can act as templates that stabilize nanoparticles; for example, encapsulation and subsequent chemical reduction of Ag(I) ions. Silver nanoparticles with a narrow size distribution (3.9+/-1 nm) have been prepared and characterized by transmission electron microscopy. Furthermore, it has been demonstrated that the encapsulated guest molecules remain accessible to small molecules after transport into the fluorous phase. Therefore, dendritic nanocarriers that contain perfluorinated shells are currently being investigated as polar environments in nonpolar reaction media such as fluorous phases and supercritical CO(2), in particular, for application in homogenous catalysis.
Garcia-Bernabé
Abel
A
Organische Polymerchemie, Universität Dortmund, Otto-Hahn-Strasse 6, 44227 Dortmund, Germany.
Krämer
Michael
M
Olàh
Bèla
B
Haag
Rainer
R