As the chemistries in both cases (a silane treatment gives rise to pure Si coatings on glass, a quartz or SiO2 on Si) of the coating and the base substrates are different, the surface properties such as surface tension will be different.

Dear Uhyeon Kim,

Here below presented some relevant sources to look at:

The surface of nano-silicon dioxide (nano-SiO2) particles was modified by small molecular coupling agent KH-560 and macromolecular coupling agent SEA-171, respectively, to change the surface activity and structure. The modified nano-SiO2 was then used for reinforcing cyanate ester resin (CE). Influences of the content of nano-SiO2and the interfacial structure over the thermal and frictional properties of nano-SiO2/CE composites were in-vestigated. The mechanism of the surface modification of silicon dioxide by KH-560 and SEA-171 was discussed. The experimental results show that the addition of coupling agents increased the interfacial bonding betweennano-SiO2 particles and the CE resin so that the heat resistance and friction properties of the composites were improved. After surface treatment of nano-SiO2 by SEA-171, the thermal decomposition temperature of the3.0 wt% nano-SiO2/CE composites increased nearly by 75 °C and the frictional coefficient was reduced by 25%compared with that of the pure CE, and the wear resistance increased by 77%. (PDF) Influences of surface modification of nano-silica by silane coupling agents on the thermal and frictional properties of cyanate ester resin.

https://www.researchgate.net/publication/324126050_Influences_of_surface_modification_of_nano-silica_by_silane_coupling_agents_on_the_thermal_and_frictional_properties_of_cyanate_ester_resin

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How does a Silane Modify a Surface?

Selecting A Silane for Surface Modification - Inorganic Substrate Perspective

Hydrophobic Silane Surface Treatments

Super hydrophobicity and Oleophobic

Hydrophobicity is frequently associated with oleo Philicity, the affinity of a substance for oils, since non-polar organic substitution is often hydrocarbon in nature and shares structural similarities with many oils. The hydrophobic and oleophilic effect can be differentiated and controlled. At critical surface tensions of 20-30 mN/m, surfaces are wetted by hydrocarbon oils and are water repellent. At critical surface tensions below 20, hydrocarbon oils no longer spread and the surfaces are both hydrophobic and oleophobic. The most oleophobic silane surface treatments have fluorinated ong-chain alkyl silanes and methylated medium chain alkyl silanes. Superhydrophobic surfaces are those surfaces that present apparent contact angles that exceed the theoretical limit for smooth surfaces, i.e. >120°. The most common examples of superhydrophobicity are associated with surfaces that are rough on a sub-micron scale and contact angle measurements are composites of solid surface asperities and air; denoted as the Cassie state. Perfectly hydrophobic surfaces (contact angles of 180°) have been prepared by hydrolytic deposition of methylchlorosilanes as microfibrillar structures. Hydrophobicity vs Water Permeability Although silane and silicone derived coatings are in general the most hydrophobic, they maintain a high degree of permeability to water vapor. This allows coatings to breathe and reduce deterioration at the coating interface associated with entrapped water. Since ions are not transported through non-polar silane and silicone coatings, they offer protection to composte structures ranging from pigmented coatings to rebar reinforced concrete. Automotive side windows are treated with fluoroalkylsilanes to provide self-cleaning properties. Water beads remove soil as they are blown over the glass substrate during acceleration. Perfect Hydrophobicity-180° The methylsilicone phase separates in ethanol to form a covalently attached fibrillar network. Fiber diameter is ~20 nm. Ellipsometry indicates a film thickness of ~20 nm. T. McCarthy, J. Am. Chem. Soc., 2006, 128, 9052. toluene-swollen crosslinked covalently attached methylsilicone CH3SiCl3 toluene trace H20 1) ethanol extraction S

Hydrophilic Silane Surface Treatments

The vast majority of surfaces are hydrophilic. Water is omnipresent in the environment, yet the precise nature of interaction of water with specific surfaces is largely unknown. Water adsorption may be uniform or in isolated patches. It may be driven by a number of different physical and chemical processes. The adsorption of water by a surface may be assisted or retarded by other adsorbents present in the environment. The purpose of applying a hydrophilic surface treatment is to control both the nature and extent of interaction of water with a surface. The controlled interaction of water with substrates can offer various degrees of hydrophilicity ranging from physics-sorption to chemin-sorption and centers for ion-interaction. The utility of hydrophilic surfaces varies widely. Anti-fog coatings exploit high surface energies to flatten water droplets rather than allowing them to form light-scattering droplets. In biological systems hydrophilic surfaces can reduce nonspecific bonding of proteins. Hydrophilic coatings with hydrogen bonding sites allow formation of tightly adherent layers of water with high lubricity in biological systems and the ability to resist oil adsorption in anti-graffiti coatings. They can also be used to disperse particles in aqueous coatings and oil-in-water emulsions. Hydrophilic coatings with ionic sites form antistatic coatings, dye receptive surfaces and can generate conductive or electrophoretic pathways. Thick films can behave as polymeric electrolytes n battery and ion conduction applications. In general, surfaces become more hydrophilic in the series: non-polar < polar, no hydrogen-bonding < polar, hydrogen-bonding < hydroxylic < ionic. The number of sites and the structure and density of the interphase area also have sig- nificant influence on hydrophilicity. Much of the discussion of hydrophobicity centers around high contact angles and their measurement. As a corollary, low or 0° contact angles of water are associated with hydrophilicity, but practically the collection of consistent data is more difficult. Discriminating between surfaces with a 0° contact angle is impossible. The use of heat of immersion is a method that generates more consistent data for solid surfaces, provided the surface does not react with, dissolve or absorb the tested liquid. Another important consideraton is whether the water adsorbed is “free” or “bound.” Free water is water that is readily desorbed under conditions of less than 100% relative humidity. If water remains bound to a substrate under conditions of less than 100% relative humidity, the surface is considered hygroscopic. Another description of hygroscopic water is a boundary layer of water adsorbed on a surface less than 200nm thick that cannot be removed without heating. A measure of the relative hygroscopic nature of surfaces is given by the water activity, the ratio of the fugacity, or escaping tendency, of water from a surface compared to the fugacity of pure water. The hydrophilicity of a surface as measured or determined by contact angle is subject to interference by loosely bound oils and other contaminants. Heats of immersion and water activity measurements are less subject to this interference. Measurements of silane-modified surfaces demonstrate true modification of the intrinsic surface properties of substrates. If the immobilized hydrophilic layer is in fact a thin hydrogel film, then swelling ratios at equilibrium water absorbtion can provide useful comparative data.

https://www.gelest.com/wp-content/uploads/Hydrophobicity-Hydrophilicity_and_Silane_Surface_Modification.pdf

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https://www.gelest.com/wp-content/uploads/Hydrophobicity-Hydrophilicity_and_Silane_Surface_Modification.pdf

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