In the big-time arenas of research, hitting the pages of Science or Nature is a slam dunk. Bring out the cameras, cut down the nets. And anyone who can do it four times in five years is burning up the league.

So picture a chemist with that kind of winning streak. He is tall, and young, and he sizes you up with a calm, predatory gaze that tells you he thrives under pressure. He prowls a big office full of honey-colored wood. He goes to the board and boils things down. He doesn't try to impress anybody with how difficult the chemistry is. He makes it look easy.

He begins with a simple idea: Carbon dioxide, the gas we are always exhaling, the gas that comes out of our smokestacks and tailpipes, has an alter ego. Under pressure, it cleans.

It cleans because Joe DeSimone, professor of chemistry, has invented a soap. Mixed with this soap, compressed carbon dioxide will dry clean your clothes. It will clean computer parts, or textiles, or a dozen other things.

When you force carbon dioxide under pressure, it becomes a liquid, like the stuff in fire extinguishers. Mix this dense CO₂ with the soap, and it lifts away the grime. Release the pressure, the carbon dioxide reverts to its pure, gaseous self, ready for more. Meanwhile, the dirt and grease are locked up in an innocent puddle of soap. No more nasty dry-cleaning fluids, no more toxic turtlenecks.

That's the idea, and it's made DeSimone's new company, MiCELL, Inc., a draw for investors and a headline-maker in the business press. For the moment, at least, no one can say why DeSimone's inventions shouldn't help clean up a whole lot of toxin-heavy industries, reducing the 30 billion tons of hazardous solvents they use each year. If that were to happen, the environment could breathe a little easier. And so could all of us.

The idea has a powerful appeal: Clean up the cleaning industry. But how did the business of cleaning become so toxic in the first place? As DeSimone explains it, it's a matter of simple chemistry.

"If you take your clothes to a dry cleaner," he says, "they use a liquid. They can't use water because your garments absorb too much water and that leaves them wrinkled, and you can't use water with silk and wool. So you have to use a non-water-based solvent."

But the water-free solvents are made from hydrocarbons, flammable organic compounds associated with fossil fuels such as oil, gas, and coal. To make these hydrocarbons non-flammable—so that people are safe to use them—chlorines are added.

"The trouble is," DeSimone says, "chlorine also makes the solvents toxic. So, if you can't use water, and you don't want chlorine, and you don't want to burn anyone, there's nothing left." Nothing but carbon dioxide.

It seems such a modest, low-tech task—to invent a soap. Something old-fashioned, like boiling up tallow and lye. But there's nothing low-tech about a soap to work with CO₂. Ordinary soap will not mix with carbon dioxide. In fact, they repel one another. That's where the chemistry gets interesting. And so difficult that, according to Eric Beckman, a University of Pittsburgh chemical engineer quoted in Science, "Lots of people gave up."

Joe DeSimone did not set out to reform the cleaning industry, or to put his name on a soap. No, he was finding ways to make polymers—plastics. Since his arrival at Carolina in 1990, much of the work in DeSimone's lab has been funded by giants of the chemical industry—first by DuPont and 3M, then by a consortium including DuPont, Hoechst Celanese, Air Products, BFGoodrich, Eastman Chemical, Xerox, General Electric, and Bayer.

One of the goals of the research was to find ways to reduce the use of special chlorinated solvents—"chlorofluorocarbons" (CFCs)—which are being banned world-wide by the Montreal Protocol because they deplete the ozone layer. CFCs are used in air conditioners and also in the manufacture of several kinds of plastics.

In 1992, DeSimone broke into the pages of Science with the discovery that certain plastics, a group of fluorinated polymers traditionally manufactured in CFCs, were soluble in liquid carbon dioxide. This meant that environmentally dangerous CFCs could be replaced with liquid carbon dioxide in manufacturing. DeSimone wanted to extend this breakthrough to other kinds of plastics.

"Most polymers are oil-based hydrocarbons," he explains. "They are oil-soluble. The fluorinated polymers we were working with turned out to be an exception. The only other solvents these polymers dissolved in were chlorofluorocarbons, CFCs. So it looked like CO₂ and CFCs were a drop-in replacement for one another in polymer synthesis."

This finding had commercial implications, and DuPont recently licensed the technique for use in manufacturing. But DeSimone and his research group wanted to make other kinds of polymers in CO₂, including acrylic latex, the stuff you find in latex paint. And that's where we come to the soap.

"Latex paint," DeSimone explains, "is a polymer dispersed in water with a soap. If the soap weren't there, it wouldn't look like milk. It would look like white powder in the bottom of a container of water."

At the board, he diagrams a soap molecule for latex paint. One side of the molecule likes water (it is hydrophilic). The other side likes oil, and therefore the oil-based plastic particles in latex paint. So the soap molecule, with its split personality, links the water and the plastic. Soap molecules are so good at this, they keep grabbing water on one side and plastic on the other until the particles are thoroughly dispersed.

DeSimone was not the first chemist to imagine how handy it would be if you could do the same thing without water, using carbon dioxide instead. The trouble was, the soaps they tried just wouldn't work in CO₂.

"Which means," DeSimone says, "that we had to redesign this thing, the soap molecule. Instead of making it hydrophilic, we had to make it CO₂-philic. And what dissolves in CO₂? Well, we showed that in 1992. It's those fluorinated polymers we were using."

The next question, DeSimone says, was, "Can we make these molecules, and will they stabilize these plastic particles?"

Yes, they could, and DeSimone's second Science paper, published in 1994, reported it to the world. The soap molecule was made of a CO₂-loving acrylic compound linked with a strand of polystyrene, a plastic-loving polymer.

"What we learned how to do was analogous to making acrylic latex paint in CO₂ instead of water," DeSimone says. "So we designed a soap to do this, and it worked. Beautifully. And this is actually a hard problem. A very hard problem."

So DeSimone and his research group knew they could make acrylic latex paint in dense carbon dioxide. And the soap they'd invented made it work. Then they remembered that soap is good for something else. It cleans.

For cleaning, the process is a little different, but the principle is the same. If you take away the plastic particles, the oil-loving ends of the soap molecules begin to band together to try and hide from CO₂. The result is a cluster of soap molecules with the oil-loving sides densely massed in the center, trying to avoid the CO₂, and the CO₂-loving sides radiating outward from the core.

"Think about how soap works in water," DeSimone says. "When you clean something, the soap molecules come together, they assemble, into something called a `micelle,' with the oil-loving ends packed together in a core. And then when you introduce a surface that has oil on it, or grease, like in your frying pan, this grease doesn't like water. It's not soluble in water. What happens is, it goes inside the core, to the part of the micelle that likes oil, and the thing just swells, the interior swells. So you lock up all of the grease inside the micelles. And that's how soap works."

By analogy, he assumed that micelles might work the same way in dense carbon dioxide. "So we laid out probably the only cleaning experiment ever reported in the journal Science," DeSimone says. "We showed that in the absence of the polymer particles, the soap molecules formed micelles. They acted like soaps do. We took a surface that had a contaminant on it, and we labeled it with isotopes. Then we watched this isotopically labeled stuff come off of the surface and go into the core, using a technique known as `neutron scattering,' so that we could see where it went. And it worked. The core grew eight hundred percent in its volume, and sucked the contaminant off the surface."

The commercial potential was obvious, and DeSimone and two of his graduate students, Jim McClain and Tim Romack, began talking about forming a company. They attracted the interest of Brad Lienhart, a former manager at Dow Chemical. With help from students in the Kenan-Flagler Business School, DeSimone, McClain, Romack, and Lienhart launched MiCELL Technologies, Inc. in 1996, attracting more than $5 million in start-up capital.

Using variations on the carbon-dioxide cleaning process, the company is developing techniques for cleaning and degreasing machinery and computer parts, for cleaning and treating textiles, and for coating metals and fibers. In June, MiCELL and American Dryer Corporation announced plans to manufacture a line of CO₂-based dry-cleaning machines. In addition to the commercial potential, there's hope for reducing the use of perchloroethylene ("perc") in the nation's $6 billion garment-cleaning industry. The U.S. Environmental Protection Agency (EPA) is asking the industry to reduce or eliminate its use of perc, a suspected carcinogen that leaves noxious fumes in clothing and generates toxic wastes requiring costly disposal.

"Removing perc is the pressure point," DeSimone says. "And the EPA thinks maybe we can help."

Botanists tell us that many green things grow faster, and yield more fruit, in an environment enriched with CO₂. That's certainly been the case with green chemistry at UNC-Chapel Hill. The growth and the breakthroughs keep coming. In September, DeSimone and several of his students and colleagues in chemistry at UNC-CH made news with an article in the journal Nature, describing a process for separating liquid chemicals. The process, a further development in the use of specialized soaps and dense carbon dioxide, could dramatically affect a broad range of industries producing pharmaceuticals, textiles, chemicals, and natural extracts such as Taxol, a product derived from the yew tree and used to fight cancer.

"CO₂ isn't the answer for every industry," DeSimone says. "And there's a lot more we need to learn. But there's a very good chance that some of those thirty billion tons of toxic solvents the world is using are about to become unnecessary. And that would be good for business, and good for the environment, too."

Cleaner, Cheaper, Smarter

Last June, Joe DeSimone, the Mary Ann Smith professor of chemistry at UNC-Chapel Hill, received the 1997 Presidential Green Chemistry Challenge Award from the U.S. Environmental Protection Agency. President Clinton established the award in 1995 to honor individuals, groups, and organizations involved in "fundamental breakthroughs in cleaner, cheaper, smarter chemistry." DeSimone, believed to be the youngest person ever to hold a chair at UNC-Chapel Hill, was the only academic chemist to receive the green chemistry award in 1997. He has also received a National Science Foundation Young Investigator Award (1992) and the Discover Magazine Environment Award (1995). In 1993, the White House named him one of 30 U.S. Presidential Faculty Members.

UNC-Chapel Hill does not have an exclusive on Joe DeSimone. He is also a professor of chemical engineering at North Carolina State University (NCSU), and his company, MiCELL Technologies, Inc., has its headquarters on NCSU's Centennial Campus. With Ruben Carbonell of NCSU, DeSimone leads the new Kenan Center for the Utilization of Carbon Dioxide in Manufacturing, a joint venture of Carolina and NCSU. While some of the engineering aspects of the CO₂ work are being developed at NCSU, DeSimone's research group at Carolina continues to pursue the basic science of polymer chemistry and carbon dioxide.

Article by Neil Caudle. Originally published in the Winter 1998 issue of Endeavors magazine.
© Copyright 1998 Endeavors magazine. All rights reserved.
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