Preparation of Fluoroalkyl End-Capped Vinyltrimethoxysilane Oligomeric Silica Nanocomposites Containing Gluconamide Units Possessing Highly Oleophobic/Superhydrophobic, Highly Oleophobic/Superhydrophilic, and Superoleophilic/Superhydrophobic Characteristics on the Modified Surfaces

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [R(F)-(CH(2)-CHSi(OMe)(3))(n)-R(F) (R(F)-(VM)(n)-R(F))] undergoes the sol-gel reaction in the presence of N-(3-triethoxysilylpropyl)gluconamide [Glu-Si(OEt)(3)] under alkaline conditions to afford the corresponding fluorinated oligomeric silica nanocomposites containing gluconamide units [R(F)-(VM-SiO(3/2))(n)-R(F)/Glu-SiO(3/2)]. These obtained nanocomposites were applied to the surface modification of glass to provide the unique wettability characteristics such as highly oleophobic/superhydrophobic and highly oleophobic/superhydrophilic on the modified surfaces under a variety of conditions. Such a highly oleophobic/superhydrophobic characteristic was also observed on the modified PET (polyethylene terephthalate) fabric swatch, which was prepared under similar conditions, and this modified PET fabric swatch was applied to the separation membrane for the separation of the mixture of fluorocarbon oil and hydrocarbon oil. The R(F)-(VM-SiO(3/2))(n)-R(F)/Glu-SiO(3/2) nanocomposites, which were prepared under lower feed amounts of basic catalyst (ammonia), were found to cause gelation in water. Interestingly, it was demonstrated that these gelling nanocomposites are also applied to the surface modification of the PET fabric swatch to give a highly oleophobic/superhydrophobic characteristic on the surface. On the other hand, the modified glass surfaces treated with the corresponding nanocomposite possessing no gelling ability were found to supply the usual hydrophobic characteristic with a highly oleophobic property. More interestingly, the wettability change on the modified PET fabric swatch from highly oleophobic to superoleophilic was observed, and remained superhydrophobic after immersing the modified PET fabric swatch into water.