A metal-sensitive organic-inorganic hybrid surfactant: POSS-capped dipicolinic acid-functionalized poly(ethylene glycol) amphiphile

A novel metal responsive organic-inorganic hybrid amphiphile with a well-defined cage structure bearing a hydrophobic polyhedral oligomeric silsesquioxane (POSS) head and a hydrophilic poly(ethylene glycol) tail functionalized with a bidendate ligand was synthesized via amidation and esterification reactions. The structure of the novel amphiphilic surfactant, aminopropylisooctyl-POSS-maleic acid-poly-(ethylene glycol)-dipicolinic acid (POSS-MA-PEG-DPA), was characterized by NMR, and its self-assembly behavior was investigated by transmission electron microscopy, dynamic light scattering, and UV-vis spectrophotometry. The experimental results revealed that the micelle morphology could be controlled by the addition of zinc ions. The proposed modulation mechanism involves the combination of hydrophobicity, metal coordination and repulsive interactions. Furthermore, the coordination bonds provide the micelles with good dynamic and thermal stability. We also found that the tadpole-shaped amphiphile could form reverse micelles with an average diameter of approximately 30 nm.