PEG-cored phosphorus dendrimers: Synthesis and functionalization

Dendrimers are macromolecular hyperbranched nano-structures, which properties are mainly driven by the type of their terminal functions. This paper reports the synthesis of dendritic structures built from difunctional polyethylene glycols (PEGs) used as core. Three different PEG lengths have been used: PEG300 (ca 6 CH2CH2-O units), PEG1000 (ca 22 CH2CH2-O units), and PEG2000 (ca 45 CH2CH2-O units). The first level of branching units is based on a dialdehyde of a dipiperazine triazine derivative. The second and third level of branching units are constituted of phosphorhydrazone linkages. The growing of the dendritic branches was found extremely slow with both PEG1000 and PEG2000 used as core, and was stopped early, whereas this problem was not observed with PEG300 used as core. These PEG-cored dendritic structures were finally functionalized on the surface with two types of nitrogen ligands.