Coating to Aid in Water, Dirt Repel


University of Massachusetts scientists say they have come up with a process for making transparent coatings that will help repel water and dirt from various substrates.

The process, as noted in Nanowerk News, could help formulators manufacture coatings that would make graffiti removal easier, for example. Unlike current processes, the researchers said, the newly developed system causes liquids to bead up and slide off, similar to the mechanisms of a lotus blossom.

The team published its findings in the journal Angewandte Chemie.

The paper, “Covalently Attached Liquids: Instant Omniphobic Surfaces with Unprecedented Repellency,” describes the process for the production of SOCAL (slippery, omniphobic, covalently attached liquid) surfaces.

Researchers Liming Wang and Thomas J. McCarthy said that glass slides using their method can be coated in minutes by dipping them in the solution, letting them dry and then rinsing them.

They state that the omniphobic coating can repel any kind of liquid.

Chemical Components

The solution contains a siloxane monomer (Me2Si(OMe)2) and sulfuric acid in isopropanol, according to Nanowerk. When an object is dipped into the liquid, a thin film of liquid forms on the surface and creates a polymer as it dries. Polydimethylsiloxane (PDMS)—a biocompatible silicone oil used in medical applications—chains form and are anchored to the surface as it is catalyzed by the sulfuric acid.

The coating is homogenous, and being so, is important for omniphobicity, noted Nanowerk. Aqueous and organic liquids reportedly roll off of coated slides without leaving a trace, even at a minimal angle of inclination.

The PDMS chains can move around as though they were in a liquid, the report said. Hexane rolls off at an incline of 1 inch, even though its surface tension is less than that of PDMS. The coatings are thermally stable and show omniphobic properties even after a year in storage, the report suggests.


Tagged categories: Coating chemistry; Coatings Technology; Dirt resistance; Graffiti resistance; Nanotechnology; North America; Research; Water repellents

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