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Rising Stars of Industrial Research

Symposium recognizes the talent and innovative contributions of young R&D scientists

September 20, 2004 | A version of this story appeared in Volume 82, Issue 38

A micrograph of Duan's nanowire thin-film transistor shows multiple silicon nanowires that serve as "log bridges" for electrical charges to cross between the yellow source and drain electrodes.
A micrograph of Duan's nanowire thin-film transistor shows multiple silicon nanowires that serve as "log bridges" for electrical charges to cross between the yellow source and drain electrodes.

American Chemical Society national meetings traditionally have not served as a major forum for industrial R&D scientists to discuss their latest research results. An obvious reason for that is the need for companies to protect their discoveries and proprietary information. Another reason is that industrial researchers' career advancement generally doesn't depend on publishing journal papers and giving talks about their research. But that doesn't mean division program chairs and symposium organizers should give up trying to encourage industrial researchers to share their expertise with the rest of the chemistry community.

With that idea in mind, the Industrial & Engineering Chemistry Division launched the first Young Industry Innovators Forum at the recent ACS national meeting in Philadelphia. The half-day symposium and reception cosponsored by I&EC and the Younger Chemists Committee was developed to recognize and foster R&D contributions of younger chemists and chemical engineers working in industry. ACS's Corporation Associates provided financial support.

"I&EC has been exploring how to better serve its members, a wide majority of whom are from industry and don't always have the opportunity to attend ACS meetings," noted Rebecca M. Chamberlin, a staff scientist at Los Alamos National Laboratory and program chair of the division. "The forum was an effort to reach out and establish a venue for technical programming that addresses industry interests and to draw in speakers from industry." It also served to recognize some of industry's "rising new stars" and to stimulate cross-fertilization of ideas among industrial scientists, she added.

Two of the invited speakers described their work on different parts of a project to develop polymer thin-film transistors (TFTs) that function as switches in electronic devices. Yiliang Wu, a scientist at Xerox Research Centre of Canada in Mississauga, Ontario, described the development of stable, solution-processable semiconducting polymers and other materials. Ana C. Arias, a research associate at Palo Alto Research Center, a subsidiary of Xerox located in Palo Alto, Calif., spoke about using the polymers and ink-jet printing techniques to fabricate TFT arrays on flexible substrates. Potential applications include lightweight displays used as electronic paper and video monitors.

One part of Wu's talk focused on the development of a liquid-crystalline polythiophene to serve as the semiconductor that bridges the gap between the source and drain electrodes of TFTs, rather than using amorphous or single-crystal silicon. Scientists have used regioregular poly(3-hexylthiophene) as the semiconductor for TFTs, Wu noted, but he and his Xerox coworkers determined that regioregular polythiophenes containing substituted and unsubstituted thiophene rings should provide better stability and TFT performance.

One of the polymers they developed has repeat units of four thiophene rings, two of which are substituted with dodecyl (C12H25) groups [J. Am. Chem. Soc., 126, 3378 (2004)]. This polymer exhibits the best all-around TFT properties under ambient fabrication conditions, Wu said.

Chappie and coworkers designed and synthesized this trisubstituted piperidine as a neurokinin 1 receptor antagonist to potentially treat pain and depression.
Chappie and coworkers designed and synthesized this trisubstituted piperidine as a neurokinin 1 receptor antagonist to potentially treat pain and depression.

ARIAS HAS BEEN designing electronic backplanes that contain arrays of printed polymer TFTs that are used to control refractive displays. The TFT base features are patterned using ink-jet printing, Arias explained. Metals and other conventional materials are patterned by digital lithography.

In one of the steps, the dodecyl-substituted polythiophene semiconductor is deposited into a preformed channel for each TFT by ink-jet printing. The accuracy of the deposition by printing is a plus for the TFT performance, reducing leakage current and cross talk between TFTs, Arias noted.

One result she described is a 128- x 128-pixel matrix (one TFT per pixel), where each pixel is 340 µm wide, corresponding to a 75-dot-per-inch resolution. "This is the largest number of printed transistors and the highest display resolution reported by ink-jet printing," Arias said. The performance of the printed TFTs is the same as TFTs made from spin-coated polymer films and approaches that of amorphous silicon TFTs, she added.

Two other materials researchers who spoke at the forum were Xiangfeng Duan, a founding scientist in the advanced technology group of Palo Alto-based Nanosys, and Mark A. Aubart, a senior research scientist in Atofina's Additives Division in King of Prussia, Pa.

Like Wu and Arias, Duan's work involves developing microscale TFTs, but he works on nanoscale electronics as well. One difference in his TFTs is that instead of an organic polymer semiconductor, he uses silicon nanowires aligned in parallel or single-crystal cadmium sulfide nanoribbons (C&EN, Sept. 22, 2003, page 7).

A key part of Duan's research has been to devise a low-temperature solution-processing method to align the nanowires as thin films. The multiple single-crystal nanowires bridge the source and drain electrodes in TFTs to ensure high charge-carrier mobility. The carrier mobility of the nanowire TFTs on a plastic substrate is around 100 times better than current technologies based on amorphous silicon or organic semiconductors, he noted.

Aubart described his work to develop polymers that act as binders for marine antifouling paints. Antifouling paints prevent growth of marine life on oceangoing ships, thereby reducing drag on the vessels to improve fuel efficiency and maneuverability, he explained. They also serve to prevent invasive species from infiltrating nonnative waters.

Traditionally, tributyltin-containing polymers have been effective in antifouling formulations because as they erode, they slowly release tributyltin oxide as a biocidal by-product. These "self-polishing" binders also control the release of biocides such as cuprous oxide that are mixed into the paint, Aubart noted. But application of tributyltin-containing paints was banned in 2003 because of toxicity concerns.

Aubart and his colleagues used high-throughput screening techniques to identify one class of replacement polymers that require low amounts of active triorganosilyl acrylate monomers. These polymers don't release a biocide by-product, Aubart said, but they do control the release of biocide additives at a low cost. Thus far, paints incorporating these silicon-based polymers are performing better in field tests than existing non-tin-based paints.

Reaction block designed by Rubin and coworkers, with the base the size of a 96-well plate, has turned into a popular lab device to carry out parallel experiments.
Reaction block designed by Rubin and coworkers, with the base the size of a 96-well plate, has turned into a popular lab device to carry out parallel experiments.

TWO PHARMACEUTICAL industry researchers who spoke at the forum were Thomas A. Chappie of Pfizer and Percy H. Carter of Bristol-Myers Squibb.

Chappie is a research scientist at Pfizer's Groton, Conn., campus working on the design and synthesis of new drugs to treat psychosis and depression. He described his role and the challenges involved in the discovery of Pfizer's potent neurokinin 1 receptor antagonist, which is being studied for its ability to alleviate pain, depression, and vomiting.

The new drug candidate was designed using knowledge gained from a previous Pfizer clinical candidate containing a disubstituted piperidine core, he explained. The research team modified an asymmetric synthesis of the disubstituted piperidine template to gain access to piperidines that have a third substituent--an alkyl group in the 6-position. This new template led to a set of compounds from which the new clinical candidate, CP-728663, was selected. Chappie also helped to design and carry out a new six-step diastereoselective synthesis of the trisubstituted piperidines.

Carter is a group leader in discovery chemistry at Bristol-Myers Squibb's Pharmaceutical Research Institute in Princeton, N.J. He discussed his work to discover small-molecule equivalents of human parathyroid hormone (PTH). This hormone is an 84-amino-acid peptide that plays a role in controlling osteoblasts and osteoclasts, the cells involved in bone formation and resorption. Human recombinant PTH has been shown to improve bone mass and reduce the risk of fractures in women with osteoporosis, Carter said.

His team developed a 14-amino-acid peptide that is a potent agonist for the receptor and showed that it induces a similar biological response as PTH. Using this shortened peptide, the researchers screened their compound collection and identified the first reported small-molecule ligand for the PTH receptor. This ligand is "an exciting lead structure" for both antagonists and agonists of the receptor, Carter said.

A. Erik Rubin, a senior research investigator at Bristol-Myers Squibb's R&D center in New Brunswick, N.J., spoke about his efforts to facilitate parallel experimentation in pharmaceutical process R&D. He is a coinventor of the MiniBlock XT, a second-generation process reactor that allows simultaneous solution-phase reactions to be carried out under varying conditions.

These multiple-reaction synthesizers are modular tools now used by pharmaceutical companies to do parallel experimentation, Rubin noted. They allow researchers to effectively explore a greater "experimental space" in a shorter period of time.

The XT is a hand-sized unit that can accommodate arrays of six to 48 glass reaction tubes. It's compatible with other types of automated lab equipment, allowing samples to be withdrawn as needed for analysis. The device allows parallel reactions to be carried out with heating or cooling, reflux, and inert atmosphere options.

THE FIRST MiniBlock system was designed by Bristol-Myers Squibb discovery scientists to carry out solid-phase reactions and isolate their products, Rubin said. His solution-phase reactor, in use at the company since 2000, is designed for process chemists who are more interested in gathering reaction data than in isolating the products. Both models have been developed commercially by Mettler-Toledo Autochem.

"There is essentially no limit to the chemistry that can be carried out in the XT, except for high pressures and extreme temperatures," he added. "We have used them for crystallizations and catalyst screening. They also have found favor in discovery labs for solution-phase compound library synthesis."

The seven speakers agreed that the Philadelphia symposium created a welcome chance to meet and share technical and nontechnical experiences with other young scientists. "The forum provided a unique opportunity to interact with young scientists in very different fields of chemistry with whom we would rarely have a chance to meet otherwise," Duan told C&EN. The interaction between people with backgrounds in organic chemistry, neuroscience, and materials science sparked a number of interesting ideas, he said.

The speakers all believed that the symposium could become a great success if it continues at future ACS meetings and more people become aware of it. "This could be a very useful symposium for college-age ACS members who are looking to understand some of the career options in chemistry," Carter added.

"I was heartened by the response of the speakers," Chamberlin told C&EN. "These rising stars, nominated by their managers, were pleased to be involved. That told me that we were doing something special."

There is a lot of encouragement to continue the symposium as a regular ACS event, she added. One possibility is to have concurrent topical sessions in different divisions, followed by a joint reception, Chamberlin said.


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