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Active Learning and Research

Summer Science Research: Jessica Mendes '05

Meet the researchers: Motion study

Chemistry major Jessica Mendes '05 became involved in research the summer after her sophomore year at Clark, working in the lab of Dr. Alan Jones. Her participation was funded courtesy of Jones' National Science Foundation grant, and this semester (fall 2003) she is continuing her work for directed study credit. Mendes has coauthored two papers, one with Dr. Jones (in process) and one with Dr. Mark Turnbull.* Below is a summary of a recent conversation during which she spoke about her research studying polymers.

(Spring 2006 Update: Jessica is now working toward her Ph.D. in Chemistry at the University of Vermont.)

What is the focus of your work in Dr. Jones' research lab?

I've been studying the motions of molecules in polymer blend systems. We're hoping that a better understanding of these motions will enable us to predict the properties of many different polymer blends and contribute to a reference database of this information.

What is a polymer, and what is a polymer blend system?

A polymer is a very large molecule. A small molecule is called a monomer. You can combine monomers to form polymers. Lots of things are made out of polymers--plastics,** foam, tires. We use products made from polymers everyday. Many polymers are made from combinations of carbon, hydrogen, oxygen, nitrogen, chlorine or fluorine atoms, to name a few. For example, PVC piping is composed of chlorine, carbon, and hydrogen. Teflon, the non-stick coating on many pots and pans, has fluorine in it.

A polymer blend system occurs when you take two different polymers and mix them in solution. It's called a blend because there's no covalent bonding between the polymers. (That means the two polymers don't "attach" to each other by sharing electrons.)

So the polymers are swishing around in solution, independent of each other?

They interact a little bit, but in a very secondary way. After we create the solution, we let the solvents evaporate out. From the resulting product we can create extremely thin films that are blends of the two polymers. Different films have different practical and commercial applications.

Can you give an example?

A lot of membrane systems are polymer blends. Some wastewater treatment processes make use of polymer blends. Fuel cells can contain a polymer membrane that separates and regulates the mixture of the fuel components.

So different polymer combinations can create membranes that exhibit different properties?

Yes, especially in regard to diffusion, that is, how fast a substance can pass through a membrane. In the fuel cell example, the hydrogen protons must diffuse through the membrane at a specific rate. Research allows us to fine-tune polymer blends to achieve the desired rate of diffusion for a given substance.

You mentioned earlier that you've been studying the motions of molecules in polymer blend systems. What are those motions and how do you study them?

The monomer units in a polymer move back and forth extremely rapidly--a small scale motion as opposed to the larger snake-like motion of the polymer as a whole. The monomers can exhibit different types of movement, including libration, internal rotation, and segmental motion.

I study segmental motion using nuclear magnetic resonance spectroscopy (NMR), a technology appropriate for studying the nanosecond time scale of segmental motion. NMR uses a giant machine with a magnet and a radio-frequency coil, attached to a really powerful computer. The polymer that we want to study is placed inside the coil, which emits radio-frequency pulses. The pulses produce detectable changes in the nuclei of the polymer's atoms, which the computer records. Based on these changes, we can make inferences about the structure and motion of the molecules made from these atoms.

Right now I'm examining segmental motions in a polycarbonate, a type of polymer that is used to make bullet-proof windows and some car windshields. Something about a specific molecular motion in a polycarbonate material allows it to be impact resistent. Recently, another scientist made a molecule that might be more impact resistant than the one currently used. So I'm comparing the segmental motion in this molecule to that in the polycarbonate currently used.

Can you comment on the advantages and disadvantages of participating in research as an undergrad? How does it compare with traditional classroom learning?

I think it's completely different. All the knowledge you learn in the classroom is very important (obviously!) and you need it to do research, but it's such a different atmosphere in the research environment. You get to do hands-on science. It's not from a cookbook lab. It's not giving you the directions every step. You have to think about and design your own process to do what you want.

You also learn what it's like to interact with people in a laboratory. You're going to get to know what it's like to go out there and work in a lab. I think it's great experience, and if you want to go to grad school they really want that research experience. And if you want to go out and get a job, it's all the better because you have it on your resume. Especially using the NMR, a specialized piece of equipment you don't really get to use in a classroom or lab.

The popular view of the scientist is someone who works in isolation, and that science is a solitary profession. But from what you describe, that doesn't seem to be true.

I work in a research group made up of both grads and undergrads. A lot of us are doing projects that complement each other, although we each have our own individual projects. But we're always consulting with each other, bouncing ideas off each other, asking for help. Someone who knows how to do one thing can show it to another person who hasn't yet learned it.

Are you planning to go to graduate school?

Yes, I'm hoping to study green chemistry. Green chemistry focuses on rethinking chemical processes that we use everyday, or in industry, so as to minimize waste and create products are less hazardous to the environment.

Jessica presented her research in a poster at Academic Spree Day 2003.
* Lee, Jong-Ho Peter '03; Lewis, Blaine D. '04; Mendes, Jessica M. '04; Turnbull, Mark M.; Awwadi, Firas F. J. Coord. Chem. 2003, 56, 1425-42. "Transition Metal Halide Salts and Complexes of 2-Aminopyrimidine: Manganese(II) compounds. Crystal Structures of (2-aminopyrimidinium)4 [MnCl4(H2O)]2, [(2-aminopyrimidine)2MnBr2(H2O)2 · 2H2O and (2-aminopyrimidinium)2+[MnBr2(H2O)4]Br2"

** The National Plastics Center & Museum, incorporated in 1982 to celebrate the birthplace of the plastics industry, is located in the city of Leominster, about 30 minutes north of Worcester by car.

A nanosecond is one-billionth of a second.

 

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Jessica Mendes
Jessica Mendes, left, and with NMR equipment, right.

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