Preparation of magnesium carbonate nanoparticles encapsulated by nanocomposite material derived from fluoroalkyl end-capped vinyltrimethoxysilane oligomer - Application to the surface modification of glass and poly(methyl methacrylate)

Sol-gel reactions of fluoroalkyl end-capped vinyltrimethoxysilane oligomer in the presence of magnesium carbonate fine particles were found to proceed smoothly under alkaline conditions at room temperature to give the corresponding fluorinated oligomeric silica nanocomposites-encapsulated magnesium carbonate nanoparticles [R-F-(VM-SiO2)(n)-R-F/MgCO3]. The obtained composites have good dispersibility in traditional organic media, and these composites are nanoparticles without agglomeration or coagulation before and even after calcination at 800 degrees C. Parent magnesium carbonate undergoes the decarboxylation at around 400 degrees C to afford magnesium oxide; however, the more smooth pyrolysis of the R-F-(VM-SiO2)(n)-R-F/MgCO3 nanocomposites can be observed at around 300 degrees C to cause the selective formation of not magnesium oxide but magnesium fluoride. The modified glass surfaces treated with the R-F-(VM-SiO2)(n)-R-F/MgCO3 nanocomposites after calcination from 200 to 460 degrees C were found to exhibit the same superhydrophobic (water contact angle value: 180 degrees) characteristic with good oleophobicity as that of the corresponding nanocomposites before calcination. The transparent colorless modified poly(methyl methacrylate) (PMMA) film was prepared by the treatment of the R-F-(VM-SiO2)(n)-R-F/MgCO3 nanocomposites to give the good oleophobicity imparted by fluorine in the composites on the modified surface. R-F-(VM-SiO2)(n)-R-F/MgCO3 nanocomposites after calcination at 200-800 degrees C were also applied to the surface modification of PMMA films, and refractive indices of the obtained transparent colorless PMMA films were found to decrease with increasing the calcination temperatures of the nanocomposites, indicating that magnesium fluoride is likely to form in the composites by increasing the calcination temperatures. (C) 2015 Elsevier B.V. All rights reserved.