New Coating Could Nix Smudges And Fogging On Glass

Date: 27 March 2007

Materials engineers have created a new type of coating that attracts water yet beads oils – traits that are usually mutually exclusive – promising potential applications such as "self-cleaning" eyeglasses and antifogging car windshields and ski goggles.

The material prevents fogging by not allowing water to form beads on surfaces, said Jeffrey Youngblood, an assistant professor of materials engineering at Purdue University.

The coating consists of a single-molecule-thick layer of a material called polyethylene glycol, and each molecule is tipped with a Teflonlike "functional group" made with fluorine. Water molecules pass through the Teflonlike layer, which acts as a barrier to the larger oil molecules. Then the water is attracted to the polyethylene glycol immediately adjacent to the glass surface.

"So, it repels the oil but not the water," said Youngblood, who is working with materials engineering doctoral student John A. Howarter. "This is important because oil normally sticks to surfaces that attract water, a property we call hydrophilic. However, we now have one that's hydrophilic but that oil doesn't like."

Findings were detailed in a talk presented on Sunday (March 25) during the American Chemical Society's 233rd National Meeting & Exposition, which takes place through Thursday (March 29) in Chicago.

The findings demonstrate how an oily substance called hexadecane beads up on the coating while water spreads out to cover the surface instead of forming beads. Moreover, when water is attracted to the underlying polyethylene glycol layer it gets between the hexadecane and the glass, dislodging the oily film.

"If you place a droplet of oil and a droplet of water right next to each other, the water will move underneath the oil and cause it to fall off of the surface," Youngblood said.

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