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November 11, 2002
Volume 80, Number 45
CENEAR 80 45 pp. 58-60
ISSN 0009-2347


TAPPING INTO NIST'S COMBI EXPERTISE
Chemical companies see value in participating in the fledgling Combinatorial Methods Center

RON DAGANI, C&EN WASHINGTON

Speed and efficiency. That's what's driving everything in industry today. It's why pharmaceutical makers adopted the combinatorial or high-throughput approach, which allows them to synthesize large numbers of compounds and screen them for useful medicinal properties--all in record time. And it's why chemical and materials companies increasingly are embracing the same strategy.

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GRADIENT GURUS Karim (left) and Amis with the flow-coater used to make thin-film polymer libraries.
PHOTO BY RON DAGANI
High-throughput experimentation, a term often used synonymously with the combinatorial approach, enables researchers to do their work more quickly, while also broadening the range of chemical substances they can examine, explains chemist John S. Sadowski, director of corporate research services at Air Products & Chemicals. "That should enable you to get products to market more quickly and help increase your probability of success."

Many chemical companies have seen the light and have made substantial investments in high-throughput experimentation. One of the newest resources or investment opportunities to attract their attention is located at the National Institute of Standards & Technology in Gaithersburg, Md. NIST's mission is to work with U.S. industry to develop and apply technology, measurements, and standards, with the aim of strengthening the American economy and improving the quality of life (see page 30). In furtherance of this mission, the NIST Combinatorial Methods Center (NCMC) was officially launched in January 2002 to help industry accelerate the pace of materials innovation.

The focus of the new center is on developing high-throughput methods for measuring the materials properties of polymers. Some of the areas being investigated include fire retardants, low-flammability polymer blends, adhesion and other mechanical properties of polymers, phase behavior of polymer blends, methods to assay the biocompatibility of polymer surfaces, and properties of multicomponent polymer formulations.

NCMC scientists also are looking for simple, clever ways to make libraries (compact collections of materials) that will be amenable to rapid measurement methods such as imaging, according to chemist Eric J. Amis, who heads the Polymers Division at NIST.

The Combinatorial Methods Center is a natural outgrowth of work that was already going on at NIST, much of it in the Polymers Division (C&EN, May 15, 2000, page 66). Indeed, the center is based in that division, although several other NIST divisions also are involved. Amis, who came up with the idea for the center, codirects it with physicist Alamgir Karim, the leader of a measurement methods group in the Polymers Division.


"It's a good outfit to be hooked up with. I think we're getting more than our money's worth."


THE COMBINATORIAL methods work in the Polymers Division will have a budget of about $2 million in fiscal 2003, and part of that is devoted to the center, which is staffed by some 20 scientists, most of them postdoctoral research associates.

Karim calls NCMC "a one-stop center," the portal of entry for industrial interactions. For an annual fee of $10,000, organizations can join the center as participating members. As of Nov. 1, 14 had already done so: Air Products, Akzo Nobel, BASF, Bayer, Dow Chemical, ExxonMobil, Gillette, Honeywell, National Starch & Chemical, Procter & Gamble, Rhodia, Rohm and Haas, 3M, and the Air Force Research Laboratory.

Amis and Karim are in discussions with other companies and expect to expand the membership to about 20. They'd also like to make the member roster more diverse. "Right now," Karim observes, "it's mainly polymers and chemical industry."

Each member organization is invited to send as many as five representatives to meetings that the center holds three times a year. At these meetings, NCMC technical advances are showcased, information on new combinatorial methods is disseminated, and current issues and needs in the field are discussed. Member organizations also can send staff to work alongside NCMC scientists on combinatorial projects. And they are provided full access to the center's website (http://www.nist.gov/combi), including a members-only section that contains technical publications, instrument schematics and specifications, automation and analysis software, and other resources.

For NIST, the center provides a way to get input on industrial needs and feedback on R&D in high-throughput methods that has been carried out at NIST for several years. For its members, the center provides them an opportunity to gain access to the technology, expertise, and facilities of NIST.

As Karim sees it, NCMC makes it easier for companies to explore the potential of high-throughput methods in collaboration with NIST scientists without feeling threatened about sharing proprietary information. That's because the center tackles problems of general interest, and all the work done there is in the public domain. The methods developed at NCMC are published and made readily available to all the members, who are then free to adapt them to their particular needs.

Kapeeleshwar Krishana, a physicist at Rhodia's Cranbury, N.J., research center, is taking full advantage of what NCMC has to offer. He attended both of the member meetings held so far this year and says they were quite useful. "But I'm getting even more value out of actually being at the center" and participating in the research, he says.

Krishana is involved in developing a new version of a flow-coater that is used at NIST to make polymer films by the gradient approach. Using this approach, researchers make film samples that vary continuously in one property, such as film thickness, from one side to the opposite side. Then they create a second gradient at right angles to the first one by, for example, exposing the sample to a temperature gradient that runs between the two remaining sides. The resulting gradient library contains every possible combination of film thickness and processing temperature within certain specific ranges. A variety of microscopy and microanalysis methods can then be used to measure the properties at any number of points on the film.

BESIDES FILM THICKNESS and temperature, NIST scientists have developed methods for producing gradients in composition, surface energy (hydrophilicity/hydrophobicity), chemical functionality, cross-link density, degree of polymerization or degradation, and height of topographic surface features.

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IN A FLASH Postdocs Christopher K. Harrison (right) and Christopher M. Stafford with the light-scattering system they developed to measure the elastic modulus of thin-film polymer libraries in a high-throughput manner.
PHOTO BY RON DAGANI
The results can be quite striking, such as the time Amis, Karim, and then-postdoc J. Carson Meredith produced a library of polymer blends using orthogonal composition and temperature gradients. In that case, the phase diagram for the blend--marked by a diffuse boundary separating one-phase and two-phase regions--was visually apparent to the unaided eye. "You could take a picture of it," Amis says. That picture, in fact, graced the cover of the American Chemical Society journal Macromolecules throughout 2001.

Once the gradient polymer-film library is in hand, the next challenge often is to develop high-throughput techniques for measuring its mechanical properties. These properties are important because they can determine how well the polymer films will perform as protective coatings, adhesives, and functional coatings in a variety of device applications.

NIST scientists recently have succeeded in developing high-speed methods to measure adhesion and elastic modulus (a measure of stiffness). The new adhesion test has the ability to provide 1,600 measurements at a time, in contrast to the conventional adhesion test that provides only one measurement at a time, Amis points out. And the new modulus test is simplicity itself: It involves shining a laser beam through a film library under strain and measuring the scattered (diffracted) light.

"This is leading-edge technology being developed at NIST," Krishana comments, and by being part of the combi center's efforts, his company can learn and benefit from them. It would be more difficult and more expensive to develop some of these tools at Rhodia independently, Krishana believes. "So being able to do this at NIST is wonderful." After all, he adds, "we don't need to invent everything by ourselves."

Other scientists familiar with the combi center express similar sentiments. The people of NCMC are viewed as "clever folks" who are developing elegant, innovative screens. "It's a good outfit to be hooked up with," says Menas S. Vratsanos, who leads a polymer characterization group at Air Products. "I think we're getting more than our money's worth."

Dow Chemical, which has an extensive in-house R&D effort in combinatorial methods and has participated in several NIST consortiums, also sees value in being part of the new combi center. NCMC's approach to synthesizing and screening combinatorial libraries is unique, remarks chemist Don Patrick of Dow. "We wanted to learn more about the applicability of these approaches to our materials programs." Participating in the center "also allows us to network with other companies that have an interest" in polymer characterization, Patrick says.

Some NCMC members would like to have a hand in directing or influencing future efforts at the center. Procter & Gamble, for instance, is particularly interested in high-throughput methods for measuring interfacial tension, according to P&G chemist Pramod K. Reddy. "Interfacial tension is an extremely important parameter that we measure day in and day out" in the company's fabric and home care division, he explains. It's of interest for almost all cleaning products, including laundry detergents, dish detergents, and shampoos, because it can be indicative of their cleaning ability.

Using existing methods, industry scientists may be able to make 10 to 20 measurements of interfacial tension per day, according to Reddy. They would like to have the capability of making hundreds of such measurements per day, but the requisite high-speed measurement tool does not exist--yet. P&G is hoping that if other NCMC members agree that such a tool is a priority for them, too, the center will take up the challenge. Reddy is confident that NCMC "should be able to develop the tool fairly quickly--I would say in less than two years' time." A third party would then be approached to manufacture the instrument, which could be purchased by a company and applied to product development.

Even if NCMC does not develop exactly what some member companies need for their particular problems, Amis explains, his hope is that company scientists will start thinking differently about the way they're approaching their problem, and maybe they'll be able to use this new way of thinking to develop something that's exactly what they want.

"Quite often," Amis says, "people will look at what we're trying to do and they'll tell me, 'Oh, you can't measure that with combi.' Now that's the sort of challenge I love."



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Cover Story
COMBINATORIAL CHEMISTRY
Advances in synthesis, purification, and analysis further refine the combinatorial approach, now a mainstream tool in drug discovery

GROWING DIVERSITY
Grants Beget New Combicenters At Pitt And BU

CASE STUDY
'A Pharmaceutical Company Would Never Do This'

TAPPING INTO NIST'S COMBI EXPERTISE
Chemical companies see value in participating in the fledgling Combinatorial Methods Center

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