In the case of having hydrophobic iron oxide nanoparticles coated with oleic acid, what happens when conducting the phase transfer process in order to add a polymer (PEG) on its surface? Does the oleic acid remain on the surface of the IONPs or does the PEG take its place? And what kind of chemical interactions happen there (how is the bonding between the chemical compounds made) ?
Thank you for your time and answers!
Hai MCI
The phase transfer process begins by the addition of a surfactant such as oleic acid to the IONPs. This helps to facilitate the transfer of the polymer molecules, such as PEG, onto the nanoparticle surface. Once on the surface, the PEG molecules form strong covalent bonds with the nanoparticles via hydrogen-bonding, ionic interactions, and Van der Waals forces. The oleic acid will remain on the surface of the IONPs, but the PEG will take its place. Thus, the phase transfer process allows for the addition of polymers, like PEG, on the surface of the IONPs that would not otherwise be possible.
Sometimes, more than one coating agents or surfactants are used together like in the following paper, where PEG chains along with tartrates are used to prepare ultrasmall Fe3O4 nanoparticles.
Article Size-modulation of functionalized Fe3O4: Nanoscopic customiz...
The attached article, Hydrophobicity, Hydrophilicity and Silane Surface Modification, examines the difference between tipped and embedded hydrophobicity on p15. The effect on iron oxide dispersion is shown in the final figure on the same page.
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