Researcher Uses Self-Assembling Molecules as 'Legos'

BUFFALO, N.Y. -- What do cell membranes, shampoo/conditioners, the ink in your ink-jet printer and thermoplastic elastomer polymers have in common?

They all contain amphiphilic molecules, which means they have an affinity for different media, allowing for distinct properties to be built into a single system or product.

These molecules, which may be block copolymers, surfactants or lipids, can self-assemble into extremely complex and often very useful advanced materials.

Paschalis Alexandridis, Ph.D., assistant professor of chemical engineering in the UB School of Engineering and Applied Sciences, has been awarded an NSF Faculty Early Career Development grant to study these extremely promising molecules. The grant pays up to $400,000 over four years with industry support.

The awards recognize young faculty members who have demonstrated outstanding potential as science and engineering investigators and educators.

The work Alexandridis is doing is geared toward making intricate structures at scales ranging from nanometer (one billionth of a meter) to micrometer (one millionth of a meter).

"Miniaturization and nanomaterials are emerging themes in science and technology," said Alexandridis. "The nanometer-length scales are not accessible by conventional machining, so we need to build them by using molecules as 'Legos.' My 'Legos' are amphiphilic molecules, and by tailoring them, we can build into them specific functions, such as molecular recognition or non-linear optical behavior."

The project is aimed at uncovering the fundamental science behind the self-assembly of amphiphilic molecules, such as block copolymers.

According to Alexandridis, the key to the research is essentially finding out how to build a desired nanostructure based on the self-assembly of block copolymers, and with the help of solvents. It also is concerned with maintaining through polymerization or crosslinking, for example, the stability and other properties of this nanostructure that are necessary to make the resulting products useful and practical.

Applications for these nanomaterials range from new catalysts for the chemical and petroleum industries to formulations of pharmaceuticals or personal-care products.

One familiar example of the principles these kinds of materials are based on is the shampoo/conditioner packaged in one bottle, says Alexandridis.

"With these products, you have two ingredients formulated together, but performing two separate functions," he explained. "First, the shampoo cleans your hair by removing the dirt and then the conditioner deposits on the hair molecules that make it smooth and shiny."

That example demonstrates the basic issues Alexandridis is studying: the fundamental problem of how to build nanomaterials and the applications of how to put these molecules together in formulations that achieve a desired function.

He currently is studying how to capitalize on self-assembly in several such systems, such as how to develop better inks for ink-jet printers by finding efficient ways to combine color and nonbleed properties in ink, as well as how to develop better contact-lens materials with the best microstructures for making them comfortable on the eye.

The most basic application of an amphiphilic molecule is the cell membrane, he explained.

"The secret of life is to keep all the important molecules in close proximity so that they can interact with each other," he said. "The cell membrane that holds things together is based on the self-assembly of lipids to form a bilayer."

Alexandridis' research is funded by the National Science Foundation, Petroleum Research Fund, Bausch & Lomb, Xerox, FlexOvit USA, Silipos, Protective Closures Co., Procter & Gamble, as well as other sources, and it involves numerous national and international collaborations.