Preparation of hydrophobic coatings
View Patent ↗A method for preparing a hydrophobic coating by preparing a precursor sol comprising a metal alkoxide, a solvent, a basic catalyst, a fluoroalkyl compound and water, depositing the precursor sol as a film onto a surface, such as a substrate or a pipe, heating, the film and exposing the film to a hydrophobic silane compound to form a hydrophobic coating with a contact angle greater than approximately 150°. The contact angle of the film can be controlled by exposure to ultraviolet radiation to reduce the contact angle and subsequent exposure to a hydrophobic silane compound to increase the contact angle.
1. A method for preparing a hydrophobic coating, comprising:
preparing a precursor sol comprising a metal alkoxide, a solvent, a basic catalyst, a fluoroalkyl compound and water;
depositing said precursor sol onto a surface as a film;
heating said film;
exposing said filmed to a hexamethyldisilazane vapor to form a hydrophobic coating with a contact angle greater than approximately 150°.
2. The method of claim 1 further comprising exposing said hydrophobic coating to ultraviolet radiation to decrease said contact angle.
3. The method of claim 1 further comprising exposing said hydrophobic coating to ultraviolet radiation to decrease said contact angle and subsequently exposing said film to a hexamethyldisilazane vapor to increase said contact angle.
4. The method of claim 1 wherein said surface is patterned to create optically defined regions.
5. The method of claim 1 wherein the surface comprises a material selected from the group consisting of a plastic, a polyester film, a fabric, glass, silicon, and metal.
6. The method of claim 1 wherein the metal alkoxide is selected from the group consisting of tetramethyl orthosilicate, tetraethyl orthosilcate, titanium teraisopropoxide, titanium tetramethoxide, titanium tetraethoxide, titanium tetrabutoxide, aluminum iso-propoxide, and zirconium n-butoxide.
7. The method of claim 1 wherein the solvent is selected from the group consisting of an alcohol, an alkane and an ether.
8. The method of claim 7 wherein the alcohol is selected from the group consisting of methanol, ethanol, isopropanol, and butanol.
9. The method of claim 1 wherein the basic catalyst is selected from the group consisting of a hydroxide, an amine or an ammonia compound.
10. The method of claim 9 wherein the hydroxide is selected from ammonium hydroxide and sodium hydroxide.
11. The method of claim 1 wherein depositing said precursor sol onto a surface is performed using a method selected from dip-coating, drainage, spin-coating, Mayer rod coating, and slot coating.
12. The method of claim 1 wherein the fluoroalkyl compound is trifluoropropyl-trimethoxysilane.
13. The method of claim 12 wherein the molar ratio of concentration of trifluoropropyl-trimethyoxysilane and metal alkoxide ranges from 0.01 to 0.15.
14. The method of claim 1 wherein said surface is the internal surface of a pipe.