WILLIAM W. GRAESSLEY (1933-2017)

BY WILLIAM R. SCHOWALTER AND
RICHARD A. REGISTER

WILLIAM WALTER GRAESSLEY, professor emeritus at Princeton University and adjunct professor at Northwestern University, passed away on Feb. 18, 2017, near Evanston, Illinois. Bill was a pioneer in developing the quantitative understanding of the dynamics of polymer melts and networks as well as the thermodynamics of polyolefin blends. His multifaceted contributions were critically important not only for advancing fundamental understanding of science, but also for applying those principles in industrial practice.

Bill was born on Sept. 10, 1933, in Muskegon, Michigan. An only child, he remained in Muskegon through his high school years, during which he experienced both the Great Depression and World War II. He earned all of his degrees from the University of Michigan in Ann Arbor: a B.S. in chemistry and a B.S.E. in chemical engineering in 1956, an M.S.E. in chemical engineering in 1957, and a Ph.D. in chemical engineering in 1960. It was during this time in Ann Arbor that he married Helen Carlsen and their three children were born. His doctoral research, during which he was an early adopter of radiation crosslinking to measure the molecular weight distribution of polymers, sparked a lifelong pursuit of understanding the connection between molecular motion and macroscopic rheology.

His career path illustrates the ease with which he moved between industrial and academic environments. After working as a group leader in polymer physics at the Air Reduction Company in New Jersey, he joined the faculty of Northwestern University in 1963, with appointments in both the Department of Chemical Engineering and the Department of Materials Science. In recognition of his impactful scholarship, he was named the Walter P. Murphy Professor of Chemical Engineering and Materials Science in 1981. One year later, Bill returned to industry as senior scientific advisor at the newly established Corporate Research Laboratories of Exxon Research and Engineering in Annandale, New Jersey. While at Exxon, he established ties with Princeton’s Department of Chemical Engineering, and in 1985, he was appointed visiting lecturer with the rank of professor. He moved full-time to Princeton in 1987 as professor of chemical engineering and transferred to emeritus status in 1998.

Bill was one of the strongest proponents of using chain entanglement concepts to explain rheological behavior in polymer liquids and crosslinked networks. He designed numerous clever experiments to test hypotheses about the nature of entanglements. While the idea of chain entanglement is now widely accepted, it was a controversial concept in the 1960s and 1970s. In his influential 1974 review in Advances in Polymer Science, “The entanglement concept in polymer rheology,” he compiled experimental evidence from the literature and discussed early theoretical ideas, emphasizing features that appeared to be universal across long-chain polymers. Building on that foundation, Bill and his students worked to differentiate the effects of crosslinks and entanglements on the modulus of polymer systems. He was among the first to recognize that in dilute polymer solutions with extremely long chains, entanglement effects could dominate without triggering the flow instabilities seen in polymer melts under strong deformation. The data generated by Bill’s group remain among the most definitive experimental studies of entanglement effects in well-defined, unsteady flows.

At the time of Bill’s move from Exxon to Princeton, he had expanded his research to include the study of polyolefin mixtures using small-angle neutron scattering (SANS). Model polyolefins could be prepared via anionic polymerization of various dienes, permitting convenient deuterium labeling through post-polymerization saturation of the double bonds. SANS then enabled accurate measurement of the Flory chi parameter — a quantification of segmental interaction strength between dissimilar polymers. Although interactions between many polyolefins are weak enough to allow miscibility, others, such as polyisobutylene, which packs more efficiently with itself than with any other polymer, revealed unanticipated mixing behavior with strong temperature dependence.

Upon Bill’s “retirement” from Princeton, he and Helen returned to their native Michigan and their house on White Lake. There, he completed his magnum opus: two interconnected books on Polymeric Liquids and Networks. Volume 1, Structure and Properties, appeared in 2004, followed by Volume 2, Dynamics and Rheology, in 2008 (Garland Science). These books presented a unified, critically evaluated, and comprehensive view of the field to which he had contributed so profoundly.

Bill’s outstanding contributions to polymer science and rheology were recognized through several major honors. These included the Bingham Medal of the Society of Rheology (1979), the Polymer Physics Prize of the American Physical Society (1990), election to the National Academy of Engineering (1990), and selection as a member of the inaugural class of fellows of the Society of Rheology (2015).

It was fortunate both for Bill and Princeton that his years there coincided with growing institutional recognition of the need to elevate the study of materials science and engineering. Bill’s wisdom — shaped by his extensive academic and industrial experience — was instrumental in the founding and development of the Princeton Materials Institute, whose scope now spans chemistry, physics, biology, and engineering.

Reminiscences from Bill’s children reflect the same qualities remembered by his former students and colleagues. He was patient, extraordinarily generous with his time, multidimensional in his interests, and a role model of high integrity to all who were fortunate enough to work with him. Yet it would be a mistake to think of him as mild or complacent — Bill was a formidable defender of what he believed to be right, whether in a technical discussion or matters of principle.

Bill enjoyed travel of all kinds, whether for business, pleasure, or often both. His children fondly remember family camping trips in national parks, but he was equally invigorated by the cultural attractions of New York City. One particularly meaningful experience was a sabbatical year (1979-80) as a senior visiting fellow at Cambridge University. That year led to a landmark 1990 publication with Sir Sam Edwards in Polymer, titled “Entanglement interactions in polymers and the chain contour concentration,” which unified the understanding of polymer melts and solutions. Bill and Helen made the most of their time in England through immersion in British culture and history, hiking the public footpaths, and attending Shakespeare performances in Stratford.

His professional legacy is well documented in an academic family tree published in the Rheology Bulletin in 2017. Spanning four academic generations, it included more than 100 names, a number that continues to grow.

Bill is survived by his wife, Helen Carlsen Graessley; his children: Kathryn G. Severin (Blaine), William W. Graessley Jr. (Maureen), and Laurie G. Frey (Steven); eight grandchildren; and eight great-grandchildren.

Authors’ Note:

In addition to the personal knowledge gained by the authors through years of close association with Bill, this memorial is based on the following sources:

1.A Memorial Resolution adopted by the faculty of Princeton University on May 22, 2017, and written by Richard A. Register, William R. Schowalter (NAE 1982), William B. Russel (NAE 1993), and Athanassios Z. Panagiotopoulos (NAE 2004).
2.An article written by Ralph H. Colby and Richard A. Register, published in 2017 in the Rheology Bulletin 86(2):18-20.
3. Information kindly provided by Bill’s three children.