Preparation of morphology-controlled fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica/magnesium oxide nanocomposite particles: development of magnesium oxide nanocomposite particles possessing a water-resistance ability

Abstract

Fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica nanocomposites-encapsulated magnesium oxide particles [RF–(CH2–CHSiO3)n–RF/MgO nanocomposites; n = 2, 3; RF = CF3CFOC3F7] were prepared by the sol–gel reactions of the corresponding oligomer [RF–(CH2CHSi(OMe)3)n–RF] in the presence of magnesium oxide nanoparticles under alkaline or non-catalytic conditions, respectively. These sol–gel reactions were found to afford the two kinds of morphology-controlled fluorinated nanocomposite particles; that is, the alkaline conditions can supply the spherical fine nanoparticles, and the non-catalytic conditions can afford the linearly arrayed fluorinated oligomeric nanocomposite particles. Interestingly, the linearly arrayed nanocomposites provide a poor water-resistance ability toward their encapsulated magnesium oxide, leading the magnesium hydroxide through the hydrolysis process; however, it was demonstrated that the spherical fine nanoparticles can give a perfect water-resistance ability toward the magnesium oxide in their particle cores under similar conditions. In addition, the spherical fluorinated nanocomposite particles-encapsulated magnesium oxide were applied to the surface modification of PMMA [poly(methyl methacrylate)] film to exhibit the oleophobic characteristic imparted by fluoroalkyl segments in the composites on the modified surface. Magnesium oxide in the nanocomposites can also have a similar surface orientational ability to that of the fluoroalkyl segments in the composites. In contrast, the corresponding linearly arrayed fluorinated nanocomposite particles can give the uniformly dispersibility toward the PMMA film to supply the oleophobic property imparted by longer fluoroalkyl segments in the composites on the surface and even on the reverse side.