December 15, 2000

NC State Engineer Develops Superhydrophobic Polymer

A sheet coated using the new MAM method (right) repels water better than a sheet coated the conventional way (left). The respective molecular alignments are depicted below the images.

It may not be nice to fool Mother Nature, but Dr. Jan Genzer, assistant professor of chemical engineering at North Carolina State University, has done just that to create a polymer with increased hydrophobic, or water repellant, properties. This new material could be used in many beneficial applications ranging from tunable insulation coatings to medical implants.

"In nature, molecules organize spontaneously into beautiful patterns," said Genzer. "It is the molecular template 'encoded' into the molecules that dictates how close the molecules can come together -- Mother Nature simply will not allow them to come closer than is convenient." With their new technique, however, Genzer and his colleagues can overcome nature's restrictions by assembling the molecules onto surfaces whose surface area can be increased (for example by stretching the film) prior to the attachment of the molecules. After the molecules are covalently attached to the stretched substrate, the substrate surface is brought back into its original size, causing the molecular arrays to reconfigure and densify beyond their natural limit.

Genzer and colleagues discovered this new technique somewhat by accident. They were searching for a substrate on which to store samples. Cellophane tape was too sticky, so they began working with the chemical bonds of polymer materials to find a surface that would adhere just the right amount. Their experimentation led to the development of a new technology that is based on what the inventors call mechanically assembled monolayers (MAMs). The researchers demonstrated the capability of this novel technique by creating MAMs from semifluorinated molecules and found that structures were less sticky than most previously developed and commercialized non-stick coatings.

Another happy accident led to additional scientific data supporting the longevity of the hydrophobic quality of the new material. While this work was going on, Genzer's lab moved to a different space and some forgotten MAM samples sat on the laboratory bench for six months. Later analysis demonstrated that the MAM surfaces were still intact after all that time.

According to Genzer, "This technique can open new possibilities for controlling the assembly of molecules on surfaces. We have found a way of independently controlling the spacing between molecules that depends on our wish, not what nature tells us."

The next step will be to study various physical phenomena that are associated with packing molecules, for example, transitions from liquids to solids. After that, Genzer's team hopes to study practical applications for this new polymer.

-- rudd --

Technical Contact: Jan Genzer (919) 515-2069 jan_genzer@ncsu.edu

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