Facile creation of superoleophobic and superhydrophilic surface by using fluoroalkyl end-capped vinyltrimethoxysilane oligomer/calcium silicide nanocomposites—development of these nanocomposites to environmental cyclical type-fluorine recycle through formation of calcium fluoride

Abstract

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer/calcium silicide nanocomposites [RF-(VM-SiO2) n -RF/CaSi2] were prepared by the sol–gel reactions of the corresponding fluorinated oligomer [RF-(VM) n -RF] with calcium silicide particles under alkaline conditions. These nanocomposites thus obtained can exhibit a good dispersibility and stability in traditional organic solvents such as methanol, tetrahydrofuran (THF), N, N-dimethylformamide (DMF), and fluorinated aliphatic solvents (1:1 mixed solvents (AK-225) of 1,1-dichloro-2,2,3,3,3-pentafluoropropane and 1,3-dichloro-1,2,2,3,3-pentafluoropropane). Methanol sol solutions of RF-(VM-SiO2) n -RF/CaSi2 nanocomposites were applied to the surface modification of glass through the dipping technique. RF-(VM-SiO2) n -RF/CaSi2 nanocomposites, in which the contents of CaSi2 are 1–8 %, can give the superhydrophobic and highly oleophobic characteristics on the modified glass surfaces. In contrast, RF-(VM-SiO2) n -RF/CaSi2 nanocomposites, in which the contents of CaSi2 are 67–88 %, enabled the modified surfaces to give the both superoleophobic and superhydrophilic characteristics. In this way, the switching behavior between the superhydrophobic and superhydrophilic surfaces with the highly oleophobic characteristic can be easily observed by controlling the contents of CaSi2 in the fluorinated nanocomposites. In addition, RF-(VM-SiO2) n -RF/CaSi2 nanocomposites were found to give the calcium fluoride as the pyrolytic product through the calcination of these nanocomposites at 800 °C, indicating that the present composites have high potential for the development to the new environmental cyclical type-fluorine recycle system.