Surface modification of silica nanoparticles using phenyl trimethoxy silane and their dispersion stability in N-methyl-2-pyrrolidone

[Display omitted] •Surface of silica nanoparticles was modified with phenyl trimethoxy silane via sol-gel reaction.•Surface modification degree was controlled by changing the amount of silane, NH4OH and water.•Hydrophobicity of silica was increased with the surface modification degree.•Dispersion stability of silica in NMP was enhanced by surface modification. Surface modified silica nanoparticles were prepared through two-step sol-gel process. The introduction of phenyl group onto the surface of silica nanoparticles could be processed by varying the amounts of NH4OH and phenyl trimethoxysilane (PTMS) and molar ratio of H2O/Si during the second step. Under the optimized condition, the surface properties of silica nanoparticles were completely different before and after surface modification, since silanol groups were substituted by phenyl groups. The qualitative analysis of modified silica nanoparticles was conducted with Fourier transform infrared spectroscopy (FTIR). The degree of surface modification at the silica nanoparticles was examined based on the surface hydrophilic/hydrophobic moiety, surface charge and morphology. The mechanism of surface modification was inferred from a surface roughness. Finally when the silica was dispersed in N-methyl-2-pyrrolidone (NMP) as organic solvent, the modified silica was better in dispersion ability at high concentration (20wt.%).