Preparation of fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica/poly(tetrafluoroethylene) nanocomposites possessing a superoleophilic/superhydrophobic characteristic: application to the separation of oil and water

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [R _F-(CH₂CHSi(OMe)₃) _n -R _F; R _F = CF(CF₃)OC₃F₇, n = 2, 3: R _F-(VM) _n -R _F oligomer] can undergo the sol–gel reaction in the presence of poly(tetrafluoroethylene) fine particles under alkaline conditions to afford the corresponding fluorinated oligomeric silica/poly(tetrafluoroethylene) nanocomposites [R _F-(VM-SiO_3/2) _n -R _F/poly(tetrafluoroethylene) nanocomposites]. Interestingly, the modified glass, poly(tetrafluoroethylene) sheet and filter paper surfaces treated with the obtained nanocomposites were found to exhibit a superoleophilic/superhydrophobic characteristic, although the original poly(tetrafluoroethylene) sheet and the modified glass surface treated with the R _F-(VM) _n -R _F oligomeric silica nanoparticles [R _F-(VM-SiO_3/2) _n -R _F] can provide the usual oleophobic/hydrophobic and oleophobic/superhydrophobic properties, respectively. The modified filter paper was applied to the separation membrane for the mixture of oil/water. In addition, the fluorinated poly(tetrafluoroethylene) nanocomposite white-colored powders thus obtained were applied to the packing material for the column chromatography to separate the mixture of oil/water and water-in-oil emulsions. We have also studied on the reusability of the present nanocomposite particle powders as the packing material for the separation of not only the mixture of oil/water but also the water-in-oil emulsions, and the colorless oil was quantitatively isolated under similar conditions even after the use of the packing materials five times.