Harnessing the Power of Polymers
9 a.m. On a sunny Tuesday morning in August, chemical-engineering professor Paula Hammond ‘84, PhD ‘93, welcomes graduate student Rebecca Ladewski to her immaculate office in Building 66. After a bit of small talk, they get down to business, fine-tuning Ladewski’s upcoming thesis committee presentation on her work investigating polymer assembly techniques for use in solar cells and batteries.
The phone rings, but Hammond ignores it. Although she has six more meetings scheduled and has just gotten off a call with a French scientist who wants to join her lab, she is completely focused on the subject at hand. “She’s never distracted,” says Ladewski. “When you’re with Paula, you have her complete and undivided attention.”
Plenty of people are clamoring for that attention. Hammond leads a research group of more than 30 members and helps run the Department of Chemical Engineering as its executive officer. On a typical day—even in the summer—her calendar is a solid blue column of meetings with students, potential collaborators, and fellow administrators. But most days she still manages to devote time to her scientific passion: designing polymers to help treat cancer or create better fuel cells and batteries.
Polymers—long chains of repeating structural units—include natural materials like rubber and cellulose, as well as myriad synthetic materials such as nylon and plastics. Many polymers have a carbon backbone to which other molecules can be attached, allowing the designer to control how the material behaves. Hammond exploits that versatility to address two of the world’s most pressing challenges. On one side of her lab, she creates films and nanoparticles that target tumor cells and deliver drugs. On the other, she’s designing polymers that can help harness and store clean energy.
Hammond and another graduate student meet with a visiting scientist from King Fahd University of Petroleum and Minerals in Saudi Arabia to discuss their ongoing project to develop polymers that can serve as more efficient desalination membranes. Her diverse research interests put her in high demand as a collaborator; the following day, she’ll meet with scientists from Dana-Farber Cancer Institute, Novartis, and Merrimack Pharmaceuticals to talk about developing her drug-delivering polymers as cancer therapeutics.
Hammond’s interest in science has deep roots. Growing up in Detroit, she dreamed of writing children’s literature and entered writing contests. But she also longed to understand how things work. She loved her science classes and found that at her all-girls Catholic high school, it was easy to become a “science nerd.”
“If you’re in a group of boys and girls, and you’re 15 or 16, and a teacher asks a question, it’s easy to defer to the guys to answer, especially in [classes like] AP physics,” she says. “It was helpful to have that freedom to feel that you could dive into this stuff and ask questions and there was no one there to look discouraging.”
Hammond’s father, a PhD biochemist who ran the health laboratories for the city of Detroit, and her mother, who founded a nursing school at Wayne County Community College, encouraged her interest, enlisting scientist friends to counsel Paula on how to achieve her goals. When looking for colleges, she came to the conclusion that MIT was the place to go. “In my mind, it was sort of the pinnacle of technology,” she says.
From the start, Hammond focused on chemical engineering, the field her high-school chemistry teacher had suggested. “I didn’t even consider the other concentrations,” she says. While taking an undergraduate course with Professor Edward Merrill, ScD ‘47, she became fascinated by polymer chemistry. “This is where the power is,” she says. “You can design these materials, and then they do these cool things.”
After graduating, Hammond spent two years in Florida as a process engineer at Motorola, where she was the only black female engineer on a staff of thousands. She then joined the polymer research staff at Georgia Tech, earning a master’s in chemical engineering. Convinced that she belonged in academia, she entered a new interdisciplinary PhD program in polymer science technology at MIT.
“Coming back to MIT was just incredible,” Hammond recalls. “Sometimes when you go away from a place and then come back, you’re a little disappointed—it’s not what you thought. When I came back to MIT, it was exactly what I had missed for the last four years.”
Michael Rubner, who became Hammond’s PhD advisor, noticed that she had a sense of purpose rare among her peers. “All grad students at MIT are brilliant, but what made Paula stand out is her … drive, motivation, and desire to succeed,” says Rubner, a professor of materials science and engineering. “Paula knew what she was going to be and what she needed to do to get there.”
For her PhD thesis, Hammond designed polyurethanes and polyesters that change color when heated or stretched. She accepted MIT’s offer of a faculty position around the time of her thesis defense and eventually took over Merrill’s polymer synthesis course. But first she spent a year and a half as a postdoctoral researcher in chemist George Whitesides’s lab at Harvard, helping refine a new technique for imprinting surfaces with micron-scale patterns. Known as soft lithography, it is now widely used to create microfluidic devices.
Hammond has an uncanny ability to take on projects unrelated to her previous work, says Whitesides. “She’s done what I think good scientists should do,” he says, “which is move from field to field, to find things you can contribute to.”
The members of Hammond’s lab trickle into a conference room on the fifth floor of the Koch Institute for a biweekly group meeting. Two grad students talk about their latest results while their lab mates munch on Thai food and offer suggestions. Hammond makes suggestions too, often asking presenters to go over a technique in more detail to build their confidence and hone their presentation skills.
This week, both presentations focus on fuel-cell research, though the lab is fairly evenly divided between energy and biomedical projects. Those two research areas developed out of Hammond’s interest in polymer construction. Since launching her research program in 1995, she has come to be considered a pioneer in a technique called layer-by-layer assembly, in which layers with different properties are laid down by alternately exposing a surface to positively and negatively charged particles. A method that she developed uses an automated spray to deposit thin polymer films over large surface areas. Svaya Nanotechnologies, a company started by a former student in 2009, has licensed the technology and is developing it to create surface coatings for semiconductors, high-definition displays, and energy-efficient windows, among other products.
Energy-related applications of her work with polymers include batteries, solar cells, and fuel cells. Last year, Hammond and her students, working with researchers at Penn State, designed a new polymer film that dramatically improves the efficiency of methanol fuel cells. Because methanol is a liquid at room temperature, these fuel cells could be much more portable than hydrogen fuel cells, allowing them to power small devices such as cell phones or laptops.
Hammond is also working with Angela Belcher, a professor of biological engineering and materials science and engineering, on batteries and solar cells that self-assemble with the help of genetically engineered viruses—research they presented to President Obama during his 2009 visit to MIT. (“It was the only time I’ve ever seen Paula nervous,” Ladewski says.)
As for Hammond’s interest in medical applications, it took root during a 2002 sabbatical at Caltech, where she became intrigued by the idea of designing polymers for drug delivery. Since then, she has developed polymer nanoparticles that zoom in on tumor sites and release their cargo when they enter the tumor’s acidic environment, as well as thin polymer films that can be designed to carry multiple drugs to a specific site and control the timing of their release. Much of the lab’s drug-delivery work is carried out with or funded by pharmaceutical companies, including Sanofi-Aventis, Johnson and Johnson, Pfizer, and Ferrosan.
Hammond keeps close tabs on all the research in her lab, meeting individually with each lab member every few weeks. If a student isn’t getting good results, she focuses on turning the setback into something positive, says grad student Dan Bonner. “Instead of seeing a negative result as a roadblock, she says ‘What is this telling us? How can we redesign our system or use it in a different context?’” he says.
Hammond wraps up the lab gathering and returns to Building 66 for a quick phone call with Darrell Irvine, an MIT materials scientist and frequent collaborator, followed by a meeting to discuss how the department might use some lab space that could become available on campus. Klavs Jensen, head of the Department of Chemical Engineering, says she is well suited to such thorny administrative issues.
“To want to do that job, I think you have to have a great deal of love and respect for the Institute and the department, because it’s really a service that you do for everybody else,” says Jensen. “You also have to have the necessary diplomatic skills and the forcefulness to say ‘This is the way things are going to be,’ but hopefully in a way that everyone feels like they had their say.”
A desire to give everyone a say led Hammond to chair MIT’s Initiative on Faculty Race and Diversity, which in 2010 produced a study concluding that while MIT’s efforts to hire and retain faculty members from underrepresented minority groups have led to some gains in recent years, the results are uneven across the Institute. As of the 2009–2010 academic year, underrepresented minorities—blacks, Hispanics, and Native Americans—made up just over 6 percent of MIT’s faculty, up from 4.5 percent in 2000–2001.
Though her schedule was already packed, Hammond felt that if she didn’t step up to lead the committee, the voices of these faculty members might not be heard. The committee began its work shortly after James Sherley, a black faculty member, staged a hunger strike in protest at being denied tenure—a decision he believed was due to his race. Hammond thinks that the Sherley case is not representative of most minority faculty experiences at MIT. However, MIT “is not a sort of oasis where there are no issues around race,” she says. “It’s a much more complex topic. I felt as if a lot of the complexities of the faculty who were going through their academic career at MIT were completely missed.”
While MIT has made progress in recruiting and retaining minority faculty, Hammond believes that more can be done. “There are places where the numbers could increase with some concerted thought and effort,” she says. “I have seen department heads who are very willing to take a look at that and see if they can engineer solutions to that. That’s what we do—solve problems.”
She also mentors minority students one on one, both formally, through MIT’s academic advising program, and informally, with students who seek her out. It’s time-consuming, but “I feel like it has to be done,” says Hammond, whose son is a junior at Northeastern University. “You get used to it, and you know that it’s a part of ensuring that the next generation moves forward.”
When she gets home from MIT, Hammond unwinds by cooking dinner and eating with her husband, Carmon Cunningham, a marketing strategist turned small-business owner. She then gears up for a few more hours of work, dealing with things that often get overlooked during the day: reading journals, answering e-mail, and deciding what to focus on in the coming weeks. As she plans her days, Hammond tries to schedule open blocks of time to puzzle out perplexing lab results, make plans for new projects, and write up scientific papers. “It’s my way of maintaining some sanity,” she says.
“In a given day, Paula is asked to do any number of things, so she has to say no,” says Robert Cohen, a professor of chemical engineering who taught Hammond as a graduate student and now occasionally collaborates with her. “She thinks about where she can have the most impact—not necessarily for her own good, but impact in general. Paula knows how to make choices, and then she puts absolutely all of her time and energy into the things that she chooses to work on.”
Having chosen to work on curing cancer, developing cleaner energy, and serving MIT, Hammond sums up her strategy for fitting it all in: “Learning what’s important and focusing on that, and finding ways to facilitate as much of everything else as you can.”
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