In the 1967 movie The Graduate, a family friend known as Mr. McGuire takes aside the confused and frustrated main character, Benjamin, and whispers just one word of advice for his future: "Plastics."

Even though it's been more than three decades since those famous two syllables were uttered, Norman J. Wagner, professor of chemical engineering, is even more optimistic that "plastics" will play an ever-increasing role in our society. He might, however, prefer to use the more scientific terms, polymers or macromolecules.

Wagner has devoted much of the past 10 years to research on various types of polymers, often in collaboration with graduate students and industry. When he joined the University faculty in 1991, he and beginning graduate student Lynn Walker began to investigate the properties of liquid crystal polymers, or LCPs, a special class of polymers whose unique optical properties enable them to be used in such applications as LED (light-emitting diode) displays. In addition, their mechanical properties make them suitable for use in high-strength applications, such as bulletproof vests and fibers for automobile tires.

Wagner explains that strands of traditional polymers can be likened to cooked spaghetti, while LCPs are much more rigid, like pencils. This rigidity leads to unique crystalline phases with important optical, mechanical and rheological--relating to the flow of matter--properties, but it also poses significant technological challenges that can hinder processing and utilizing LCPs in many applications.

Walker, EG '95PhD, now on the faculty at Carnegie-Mellon University with a substantial research program of her own, designed and built a novel device for interrogating the molecular-level architecture of LCPs, with support from the National Science Foundation.

"Lynn combined rheological and laser-light scattering measurements in developing equipment that gave us a whole new way of studying LCPs under processing-like conditions," Wagner says. "With this technique, we were able to go beyond simple measurement of mechanical and bulk properties to look at the microstructure of the materials and how it's affected by processing."

Wagner uses simple analogies from the kitchen to illustrate: "Rheology is the study of the flow of matter. Viscosity is something we're all familiar with--honey, pancake batter and ketchup, for example, all flow differently. They also react differently to heat, which is just one 'processing condition.' Ketchup and honey become less viscous when they're heated, but pancake batter turns into a solid on a hot griddle. Similarly, polymers, depending on their molecular structure, can undergo significant change during processing. This microstructure-property relationship is what we're investigating, and Lynn's work gave us new tools to use in doing that."

The DuPont Co. played a major role in the work, Wagner says, providing not only regular intellectual exchange and funding but also a variety of unique materials for the UD team to study.

"With DuPont, our initial scientific investigation broadened to exploring materials that might be more industrially relevant, as well as to seeking new uses for existing LCPs," he says. The collaboration also involved the National Institute of Standards and Technology (NIST) in Gaithersburg, Md., whose world-class, small-angle neutron-scattering facility was used to measure the molecular architecture of polymers under flow.

"This project demonstrated to me that academia, government and industry could collaborate successfully and that students could be educated while doing useful scientific and engineering research," Wagner says. "That approach became the model for my future research and teaching."

Maria Rivera-van Eijndhoven, EG '97PhD, who currently is employed by DuPont, was the next graduate student to work on Wagner's team in this area. Her work exploited the unique rheology of LCPs to make fully recyclable, high-strength composite materials through a melt-phase blending process. Composites are typically produced using a two-phase approach, where the reinforcing fibers and the polymer matrix are made separately and then combined in a manufacturing process.

"The new material resulting from the transformation brought about by this blending and shearing process takes advantage of the strength of the LCP but at a lower cost and with improved properties because of the blend," Wagner says. "What we accomplished with this in-situ process was to create the reinforcing fibers during processing rather than adding them to the matrix later."

Wagner continued to collaborate with the DuPont Co., and, with his next student, Bill Kernick, EG '98PhD, the work turned back in the direction of basic science. "What we were doing was repeatedly crossing that bridge between science and engineering," Wagner says. "We started by investigating pure LCPs and then turned to processing issues. Once new processes had been developed, we went back to seeking a better understanding of what the processing does to the materials."

With the LCP area relatively mature, Wagner recently began exploring a new class of polymers. He and current graduate students Brian Tande and Jan Boshoff, in collaboration with Prof. Michael Mackay, EG '79, at Michigan State University, began to investigate dendrimers, which have a highly branched, tree-like structure. The pencil-like LCPs and the spaghetti-like traditional polymers are both linear, which means that each chain has only two ends, but the hyperbranched dendrimers have many end groups.

"We can attach things to these end groups for a variety of applications," Wagner says, "including drug delivery systems, catalysts and advanced composite materials. We're working with chemists at DuPont to vary the chemistry of these polymers and make new structures. Our focus is not on any particular application but on developing a scientific understanding of how these materials behave differently from normal, linear polymers."

The group also is using simulations to predict the molecular structure and thermodynamic properties of dendrimers, with such potential uses as processing aids and novel materials. This research benefits from the new Rheological Laboratory, which was funded by a Major Research Initiative Program of the National Science Foundation and awarded to 14 UD faculty members involved in rheological science. It is operated through Wagner's laboratory.

With graduate student Beth Schubert, Wagner also is collaborating with Dean of Engineering Eric Kaler and Unilever to investigate yet another class of materials--self-assembled surfactant systems.

"These materials have polymer-like properties, but they're strongly affected by processing because they break very easily," Wagner says. "It's a real challenge for industry to achieve the desired properties with these materials. What we're doing is applying all of the investigative tools we've developed in our work with other polymer systems to self-assembled surfactant systems, in an effort to shed new light on the structure-property relationships of these materials."

As polymers are truly "nanostructured" materials, Wagner and four faculty colleagues recently were awarded one of seven prestigious National Science Foundation Nanoscale Modeling grants to establish a nationwide network of expertise in the nanosciences and engineering. Housed primarily in UD's Colburn Lab, the group applies quantum mechanics, molecular dynamics and parallel computing methods to model new nanostructured materials, from dendrimers and glassy polymers to carbon nanotubes and nanoporous carbon membranes. This work is focused primarily on understanding and predicting the properties of these materials for use in separations.

Another of Wagner's new areas of investigation is bio-polymers. In collaboration with researchers from the College of Agriculture and Natural Resources and industries including Kodak, Hercules and BASF, he is looking at materials such as gelatin, which has applications in photography and pharmaceutical formulation; xanthan gum, which is commonly used as a food additive; and tobacco mosaic virus, which is a model system for LCPs. This research also includes visiting graduate students from Germany, Australia and other countries.

Regardless of the material being studied, several themes have run through all of Wagner's research on polymer materials during the past decade. The first is the strong foundation in rheology and polymers laid by eminent Delaware scientists and engineers, such as H. Fletcher Brown Prof. Emeritus Arthur Metzner and others, many associated with the Center for Composite Materials, beginning a generation ago.

"The network of people working in rheology and polymer science at UD transcends departmental boundaries," Wagner says. "It includes contributions by people in chemistry, mathematics, engineering and agriculture."

The second theme is students. Wagner can't say enough good things about the graduate students who have worked in his research group during the past 10 years. "They have an intense interest in the field and tremendous creativity," he says. "Their drive is what really helped us create and sustain our expertise in this area. I've also worked with more than a dozen undergraduate researchers along the way, who have assisted at all levels of the research and made great contributions."

Finally, Wagner mentions the importance of industrial collaboration in making the transition from science to engineering practice, and back to science again, to develop further understanding. "It's been very easy to make that connection in Delaware," he says.

"The sky's the limit with polymer science," he concludes. "Now that we are developing the ability to integrate biology into more of our technology, polymers will play an even greater role in our everyday life, as we learn how to design them for specific purposes, just as nature has done so successfully. There are lots of opportunities out there, in applications ranging from medicine and spacecraft to cars and sporting equipment."

Sounds like Mr. McGuire's advice to Benjamin was right on.

--Diane Kukich, AS '73, '84M