Hydrophobically Modified Halloysite Nanotubes as Reverse Micelles for Water-in-Oil Emulsion

An easy strategy to obtain inorganic reverse micelles based on halloysite nanotubes (HNTs) and alkyltrimethylammonium bromides has been developed. The selective modification of the HNTs external surface with cationic surfactants endows to generate tubular nanostructures with a hydrophobic shell and a hydrophilic cavity. The influence of the surfactants alkyl chain on the HNTs functionalization degree has been investigated. The dynamic behavior of the surfactant/HNT hybrids in solvents with variable polarity has been correlated to their affinity toward hydrophobic media explored through partition experiments. The water-in-oil emulsion is able to solubilize copper sulfate, proving the incorporation and the loading of hydrophilic compounds into the HNTs lumen. Here we have fabricated ecocompatible reverse micelles with tunable hydrophobic/hydrophilic interface that might be suitable for industrial and biological applications as well as for selective organic synthesis.