Supramolecular colloidosomes based on tri(dodecyltrimethylammonium) phosphotungstate: a bottom-up approach

Hybrid tri(dodecyldimethylammonium) phosphotungstate ([C12]3[PW12O40]) amphiphilic nanoparticles self-assemble in situ at the water/toluene interface to form stable water-in-oil (W/O) Pickering emulsions (droplet size ≈ 20 μm). These emulsions are used as a template for the preparation of colloidosomes (ϕ ≈ 5 μm), which are produced solely through the self-assembly properties of the [C12]3[PW12O40] nanoparticles into a "fused" phase on the water-drop surface in contact with toluene. The structure of the emulsions has been determined using optical and cross-polarized light microscopy, while the colloidosomes have been characterized by scanning electron microscopy (SEM). The structure as well as the aggregation behavior of these nanoparticles has been investigated. Small- and wide-angle X-ray scattering (SWAXS) and transmission electron microscopy (TEM) experiments have revealed a lamellar organization of the inorganic polyoxometalate anions because of the van der Waals interactions between the alkyl chains of the organic cations. According to the solvent, the internal molecular arrangement inside the nanoparticles can be modified: in water, the nanoparticles tend to aggregate in a lamellar structure, whereas in toluene, the nanoparticles are "fused" or coagulated.