Surface Geometric Structure of Chemically Modified Silica Studied by Direct Atomic Force Microscopy (AFM) Imaging and Adsorption Method

Abstract

The relationship between wettability and surface geometric structure of modified silica particles and glass plates was investigated. Surface modification was performed by the autoclave method with 1-dodecanol to control the surface wettability. The preferential dispersion test proved that wettability varied at a surface modification ratio of 20%, which coincided with the changing point of the geometric structure of modifier chains determined by the adsorption method. The geometric structure was also evaluated by atomic force microscopy (AFM), and we could obtain the hexagonal packing of chains of the modifiers both in water and air at high surface modification ratio. Imaging of the surface of the nanosized particles on a glass plate was accomplished in water by taking advantage of the hydrophobic attractive force, which was proved by adhesion force measurements.

Small-Angle Neutron Scattering Studies of an Adsorbed Non-Ionic Surfactant (C12E24) on Hydrophobised Silica Particles in Water

“…TGA showed the area per molecule for the grafted 1-octadecanol on SG196 was 0.31 nm 2 , which gave a grafted mass per unit area of 1.4 mg m -2 using the specific surface area derived from the BET equation. This value is slightly larger than that found by other authors …”

Cationic electrolyte adsorption layers on hydrophilic and hydrophobic surfaces

“…Thus, the coatings applied on the HMDS modified capillaries by the above described procedure may be considered stable and hydrophobic. CPE adsorption was studied by the capillary elec trokinetics method [16][17][18][19][20][21][22][23][24][25][26][27][28][29], which makes it possible, based on the measurements of the streaming potential and current in a thin quartz capillary, to calculate the electrokinetic potential (ζ potential) by the Helm holtz-Smoluchowski equation ζ = ηK × ΔE/εε 0 ΔP, where ΔE is the streaming potential, which is deter mined from a plot of the voltage current characteristic of a capillary; ε is the dielectric permittivity of a medium; ε 0 is the dielectric constant; ΔP is the pres [10]; in this case, the intercharge distance is 5.2 Å [30].…”

“…The essence of the modification consists in the chemical binding of silanol groups with the formation of ≡Si-O-Si(CH 3 ) 3 bridges. The hydrophobic properties begin to mani fest themselves when the degree of quartz surface coverage with trimethylsilyl (TMS) groups reaches 50-60% [16].…”

“…Modification of both porous and nonporous quartz with OSCs has been widely investigated using IR and NMR spectroscopy and other methods [15][16][17][18]. The properties of a modified surface have appeared to depend on the amount of functional groups grafted to it, while the reactivity of residual free silanol groups to be substantially lower than that of the groups on a pure surface.…”