| Abstract
| - We control the hydrophobicity of submicrometer silica spheres by modifying their surface with −CH3, −CHCH2,−(CH2)2CH3, −CH2(CH2)4CH2−, −C6H5, −(CH2)7CH3, and −(CH2)11CH3 groups through a modified one-step process.The scanning electron microscopy (SEM), quasi-elastic light scattering (QELS), UV−visible spectra, nitrogen sorption,and water vapor adsorption methods are used to characterize the particles. The SEM micrographs of the particlesdemonstrate that the modified particles are uniformly spherical, monodisperse, and well-shaped with the particle sizeranging from 130 to 149 nm depending on the modified organic groups. In aqueous solution, the particles modifiedwith phenyl groups have an obvious UV absorption peak at around 210 nm, whereas the other modified particles andunmodified particles do not have any UV−visible absorption peaks. There exist obvious differences in the amountof water vapor adsorbed depending on the type of surface functional groups of the modified particles. Compared withthe unmodified particles, the modified particles have a lower water vapor adsorption because of the improvedhydrophobicity of the particle surface. As a potential application, we prepared polystyrene/SiO2 nanocomposites byblending polystyrene with the synthesized particles. Water contact angle measurements show that the surface of thecomposite prepared with the modified particles are more hydrophobic. Confocal microcopy demonstrates that theparticles are less agglomerated in the nanocomposite as the particles become more hydrophobic. These comprehensiveexperimental results demonstrate that the hydrophobicity of the particles can be easily controlled by surface modificationwith different organosilanes through a modified one-step process.
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