How Does a Silane Modify a Surface?
Most widely used organosilanes have one organic substituent and three hydrolyzable substituents. In most surface treatment applications, the alkoxy groups of trialkoxysilane are hydrolyzed to form silanol-containing materials. The reaction of these silanes involves four steps. Initially, three unstable groups were hydrolyzed. Condensation to oligomers. Then, the oligomer is hydrogen bonded to the 0H group of the substrate. Finally, during drying or curing, a covalent bond is formed with the substrate while losing water. Although described in sequence, these reactions can occur simultaneously after the initial hydrolysis step. At the interface, there is usually only one bond from each silicon of the organosilane to the substrate surface.
The remaining two silanol groups exist in condensed or free form. The R group can still be used for covalent reaction or physical interaction with other phases.
Silane can modify the surface under anhydrous conditions that meet the requirements of single layer and vapor deposition. Usually the reaction time (4-12 hours) is extended at high temperature (50*-120°C). Among alkoxysilanes, only methoxysilane is effective without catalytic vapor deposition. The most effective silane for vapor deposition is cyclic azasilane.
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