Arthur L. Robinson

Third NSF decadal report presents challenges for polymer field

“F the polymer community, this is huge. It is the third such study, each charting the key challenges for the fi eld in the coming decade,” says Richard Vaia of the Air Force Research Laboratory at Wright-Patterson AFB, Ohio, on the recently released report of an August 2016 National Science Foundation (NSF) workshop “Frontiers in Polymer Science and Engineering.” Vaia joined workshop initiator Andrew Lovinger of NSF and Kathryn Beers of the National Institute of Standards and Technology in supporting workshop chair Frank Bates of the University of Minnesota, Twin Cities, and a cadre of workshop co-organizers. More than 70 workshop participants spanned the range from academic to industrial and government researchers. The report is notable because it spans the entire fi eld of polymer science and engineering. “The polymer scope is enormous, and it’s only getting bigger,” says Bates, “so it was once again timely to evaluate the fi eld in its entirety, including a look at how it impacts science and society.” For all three decadal polymer overviews, Lovinger sought the co-sponsorship of several federal agencies supporting polymer research. “I wanted these workshop reports and their recommendations to be seen not just as refl ecting NSF priorities, but as indicative of the interests of agencies across the government,” he says. The two prior workshop reports were very prophetic. Many of the challenges and opportunities identifi ed evolved into major efforts within the polymer community and also across a wider range of research fi elds. Starting with the monomers from which they are constructed, polymers fi t naturally into the nanoworld, and the 1997 report had nanoscience as one theme. Its recommendations anticipated initiatives at NSF and elsewhere as the nano-revolution was taking hold throughout the research world. Similarly, the 2007 report highlighted the importance of energy and environmental sustainability, cornerstones of subsequent NSF initiatives in solar energy and sustainable chemistry and materials. And they continue to draw widespread attention today. Where will the 2017 report have the biggest impact? NSF’s Lovinger is making no predictions. “We are trying to grow the entire fi eld without giving the impression that we have favorites,” he says. For those seeking clues to the future, the report’s Executive Summary identifi es four broad themes and overarching concepts that resonated with the workshop’s participants: Integration from nanometers to meters, advanced instrumentation, ubiquitous theory and computation, and bridging the academia–industry divide. The executive summary in the report also lists scientifi c and engineering themes that cross through the eight sections in the document. Each section, in turn, identifi es “grand challenges” and concludes with its own set of recommendations (see Table I). Of the four broad themes identifi ed in the Executive Summary, Bates calls attention to the transition of theory (computation and simulation) from a separate subject to one inextricably bound to experiment. “Theory is important in every area of polymer science and engineering,” said Bates, “and it needs to be in concert with experiment through the formation of close collaborations.” Bates cites the example of precision chemistry (Section 2: Macromolecular Synthesis), where there have been major advances in the synthesis of large molecules, as a probable benefi ciary of close collaboration with theorists. “Chemists can make almost anything,” he said, “and they are now aiming to rival what can be done in the biological world. Combining this kind of precision chemistry with theory and simulation will create engines for innovation and discovery.” The Air Force’s Vaia agrees, noting an exciting convergence among (1) simulation and big data to frame the complexity of polymers that arises from their hierarchy of structure and relaxation times; (2) chemistry, where techniques are developing toward sequence specifi c control; (3) biochemistry, where synthetic and systems biology are enabling microbes to synthesize fi ne chemicals; and (4) characterization tools that enable detailed (location specific) nanoscale insights into composition, structure, and processes. “Together these are the four critical components of a revolution in molecular-level engineering.” Section 3 (Hierarchical Structures at Multiple Length Scales and Energy Scales), for example, points out that polymers are capable of simultaneously achieving order over a wide range of length scales. These hierarchical assemblies form due to an interplay between thermodynamic and kinetic driving forces acting through the atomic (monomer), nanoscopic (monomer sequence, chain shape), and mesoscopic length scales. Order at every length scale affects both the structure and function of the resulting polymers. “Those forces acting on the microscopic functional groups have to be transferred and amplifi ed via hierarchical structures at different length scales to generate the macroscopic properties,” says Stephen Cheng of The University of Akron. “Therefore, designing building blocks and assembling modules via different interactions are the key pathways to creating new polymer materials.” While the future looks promising for the fi eld, many challenges remain. Murugappan Muthukumar of the University of Massachusetts Amherst, names the nonequilibrium (and hierarchical) structure and dynamics of polymers as one of the major ones. “There is a lack of understanding [of nonequilibrium effects] in the polymer fi eld,” he says, giving polymer crystallization as an example. “There is a hierarchy over energy, length, and time scales of nonequilibrium assemblies emerging from baby nuclei that grow and decay, with survivors becoming