John Douglass Ferry
Fields of Interests
Selected Awards, Honors and Societies
Rheologica Acta Dedication [Vol. 36, No. 3 (1997)]
This issue of Rheologica Acta is dedicated to John D. Ferry, Emeritus Professor of Chemistry at the University of Wisconsin-Madison, who celebrates his 85th birthday on May 4, 1997. He is undoubtedly the most widely recognized research pioneer in the study of motional dynamics in macromolecular systems by viscoelastic techniques, and thus has played a truly major role in polymer rheology. From the beginning of his career he realized that the unique physical properties of polymeric materials are intimately linked to the motions and configurations available to large, flexible macromolecules. He has made an extensive and concentrated effort to determine experimentally the relation between the chemical structure of well characterized samples and the resultant dynamic viscoelastic properties exhibited by them, both for naturally occurring macromolecules of biological importance and the synthetic polymer systems of particular interest to the chemical sciences and industry.
John's fundamental studies of rubbers, polymer melts and polymer solutions provided the foundation in mechanical properties for polymer scientists in both academia and industry. His book Viscoelastic Properties of Polymers first appeared in 1961, and rapidly became a standard reference for researchers in the polymer field. At that time, molecular theories of polymer dynamics were still rather new (the Rouse theory appeared in 1953; the Zimm theory in 1956). Therefore, the book was devoted primarily to a presentation of phenomenological theory, a detailed summary of experimental results on a wide variety of polymer systems and an extensive discussion of the dependence of viscoelastic properties on temperature. The latter reflected his very important work relating the temperature dependence of chain relaxation times to free volume via the WLF (Williams, Landel and Ferry) equation for time-temperature superposition which has played such a key role in polymer rheology. He discussed viscoelastic behavior of amorphous polymers in terms of three important temporal regimes, each with different molecular phenomena playing key roles: the rubbery regime, the transition zone linking the rubbery and glassy regimes, and the glassy regime. The second (1970) and third editions (1980) reflect the major advances in polymer theory and refinements in experiment that had occurred subsequently. His encyclopedic knowledge of his field, his vast number of original research contributions, and his thorough and impartial presentation of experimental results and theoretical interpretations enabled him to produce these outstanding research treatises, works that became the bibles of mechanical properties of polymers. The book generated sufficient worldwide demand to be translated into three languages - Japanese, Russian, and Polish. His research publications list with more than 280 entries dealing with macromolecules, attests to his interest in and extensive contributions to polymer science.
John Ferry's role in the development of rheology and an understanding of the links between viscoelastic properties and molecular structure has been so important that it is appropriate to recall and recognize these achievements on this occasion. He began to work with polymers as an undergraduate, at a time when the identification of polymers as giant molecules was still being contended. He has given us an enormous legacy of understanding of both the linear viscoelastic properties of polymeric systems and the physical origins of these properties in the conformations and motional dynamics of these macromolecules, developed by him and his collaborators during the last 50 years. Some of the most notable contributions to rheology from his group are:
The simple but key principle of reduced variables, giving mathematical form and physical basis for time-temperature superposition (he named the shift factor aT; a similar reduced variables approach to concentration dependence (shift factor ac). This principle enabled one to describe the response of a polymer or polymer solution in terms of the relaxation spectrum H (ln ) and aT or aC; i.e., one now could examine separately the time or temperature dependence of the viscoelastic properties. (Three research pioneers contributed substantially to this concept: Leaderman discussed its potential application to mechanical, dielectric, and magnetic relaxation experiments in 1943; Andrews and Tobolsky used empirical shifts along the log time axis to construct "master curves" in 1945; and Ferry formulated plotting methods for the components of the complex shear modulus and complex viscosity in 1950, and subsequently this approach in complete form in his book.)
Extensive, detailed and thorough studies of the viscoelastic properties of various well-characterized polymers to test the validity of the reduced variables concept and to examine the dependence of H on polymer structure. Here the choice of polymers was critical, partly because of limitations in instrumental working frequency and temperature.
The development of the WLF equation and detailed examinations of the relation between the temperature dependence of viscoelastic properties and free volume. This work provided a major paradigm shift for rheology, in establishing for the first time both a defined reference temperature state instead of the - until then - arbitrarily chosen one and the corollary free volume concept and its role.
Use of concepts elucidated by the Rouse theory (dilute solutions ) linking conformational dynamics and viscoelasticity to explain reduced variables and give an explicit form for H; extension of Rouse theory to try to explain bulk polymer behavior.
Application of the extended Rouse theory to his celebrated study of the glass-to-rubber transition zone employing methacrylate esters so that the influence of chemical structure and side-chain length could be explored. This showed that the relaxation spectra were essentially identical; i.e., the character of the frequency dependences seen was essentially identical except for overall sample-dependent temporal shifts that were expected from material-dependent molecular parameters of the modified Rouse theory, such as the monomeric friction coefficient and the fractional free volume.
Extensive studies of the role of entanglements in viscoelastic properties of bulk polymers and concentrated solutions that led to an explanation of the magnitude and breadth of the entanglement plateau. This work showed the importance of the molecular weight between entanglements, Men, as a key parameter in determining observed viscoelastic properties, and the effect of entanglement coupling on viscoelastic properties. Later, even more extensive studies of the plateau zone enabled him to demonstrate that in this regime there was no change in mechanism with time scale or with temperature. The extent of entanglement was varied by selecting different chemical structures -- (PIB, SBR, Hevea, polydimethylsiloxane) or by modifying the type and extent of branching.
Detailed investigations of the effect of trapped entanglements in crosslinked systems. The trapped entanglement treatment worked out by Langley and Ferry probably is still the best, most comprehensive description of such systems to date as judged by agreement with experiment. Ferry's use of two-network experiments, together with his adaptation of a two-network theory, enabled him to explain the properties of systems that included both permanent and "transient" crosslinks.
Definitive experiments demonstrating the relation between small molecule diffusion in a rubber matrix and the monomeric friction coefficient for the matrix chains.
Extensive high precision viscoelasticity studies of very dilute solutions for a wide variety of synthetic and biopolymers. These measurements were sufficiently precise to provide reliable extrapolations to obtain the infinite dilution properties required for quantitative tests of the elegant statistical mechanical theories of Kirkwood, Rouse, Zimm, Tschoegl, Peterlin, and others. Ferry's group was the first to obtain, on an extensive scale, infinite dilution properties. These studies explored the role of molecular weight, molecular weight distribution, chain flexibility, side-group size, long-chain branching, solvent quality and charge screening (polyelectrolytes) in the observed viscoelastic properties. They were the first to note that fairly rigid biopolymers frequently exhibit behavior reflecting a combination of overall rotatory and flexural motions rather than the "entropy spring" behavior of flexible chains.
Development of unique, specialized, high precision instrumentation. One of the principal reasons that John Ferry has made such wide-ranging and unique contributions to our understanding of the role of molecular motions in rheology is that with each move to a different area he and his collaborators developed new instrumentation that could probe the requisite temporal regimes; such instrumentation was not - and to a large degree still is not - available commercially. Generally, experimental studies of chain dynamics via viscoelasticity have substantially preceded theoretical understanding, due largely to the unique and enabling instrumentation and resultant investigations of John Ferry and his collaborators.
On the personal side, John is almost certainly the only polymer scientist to have been born at Dawson in the Yukon Territory of Canada. He spent his first two years living in log cabins in that immediate area since his father was a civil and mining engineer specializing in prospecting for placer deposits. Perhaps his early years in that cold environment are the reason why he has tended to be most interested in polymer properties at temperatures well above Tg! [These early years are capably and interestingly documented by Eudora Bundy Ferry, John's mother, in her book Yukon Gold: Pioneering Days in the Canadian North, Exposition Press, New York (1971)]. Most of John's childhood was spent in small mining communities in Idaho and Oregon; he attended a one-room school in the ghost town of Murray, Idaho, and completed the eight grades in four years with what he describes as "somewhat uneven training." At age eight he had a boy's size "rocker" for processing gold-bearing gravel. Later, he helped his father survey and assay placer gold; he is still an expert with a gold pan, employing all the correct swirling and shaking motions. The town of Murray was similar to Dawson in that the family was snowed in from November to May; a trip to the doctor was an all-day affair by horse-drawn sleigh over two mountain passes. During high school John taught himself enough Latin and German to later go into advanced classes in these subjects. This fascination with language has persisted as his most extensive avocation.
John attended Stanford University, receiving the A.B. degree in 1932. In those days Stanford's Department of Chemistry each year selected and prominently displayed on a silver cup the name of the outstanding freshman chemistry student. In 1929 John's name was posted; in 1930 David Packard, who later became the Packard of the Hewlett-Packard Company, was selected. John completed the Ph.D. degree in 1935, also at Stanford. Between degrees he served as an attached worker at the National Institute for Medical Research in London, where he worked with W.J. Elford on the general problem of ultrafiltration of proteins with graded collodion membranes. One day F.M. Burnet - now Sir Mcfarlane Burnet - appeared with some special viruses to be separated, which eventually resulted in an esoteric joint publication entitled "The Differentiation of the Viruses of Fowl Plague and Newcastle Disease."
John's first employment after graduation was as a private research assistant at the Hopkins Marine Station of Stanford University, where he worked for a year with Dr. David Spence, the 1941 recipient of the first Charles Goodyear Medal. (John received the Charles Goodyear Medal in 1981.) He then served as instructor and tutor in biochemical sciences at Harvard University, and subsequently became a Junior Fellow of the Society of Fellows at Harvard which enabled him to pursue studies of his own choice, which were centered on the viscoelastic properties of polymers. During the second world war he held a joint appointment at Woods Hole Oceanographic Institute and the Harvard Medical School. At Woods Hole he worked on antifouling paints for marine applications; at Harvard he was attached to the E.J. Cohn Project, which had as its overall objective the large scale fractionation of human blood plasma proteins for clinical use by the U.S. Armed Forces. This work began a career-long interest in fibrinogen and its conversion to fibrin, and the general problem of blood coagulation. The unit to which John was attached had as its assignment the conversion of fibrinogen to various useful forms. The group produced two particularly useful materials: a fibrin foam that found extensive use for the stoppage of bleeding during tooth extraction, brain surgery, and other surgical procedures; and a fibrin film, the product of a collaboration between John and Dr. Peter Morrison, which became the first safe and effective surgical replacement for the dural membrane that lines the brain cavity. John and Peter also produced interesting plastics by heating fibrinogen with glycerol. In 1946 John joined the faculty of the Department of Chemistry of the University of Wisconsin as an Assistant Professor; by 1947 he had been promoted to full Professor. He served as Department Chairman from 1959 to 1967 and was appointed Farrington Daniels Research Professor in 1973. He was a founding member of the Rheology Research Center at Wisconsin, serving on its Executive Committee until 1984.
Throughout his career John has received many national and international awards, including membership in the National Academy of Sciences, the Eli Lilly Award in Biological Chemistry of the American Chemical Society, the Bingham Medal of the Society of Rheology, the Colloid Chemistry Award of the American Chemical Society, the High Polymer Physics Prize of the American Physical Society, the Colwyn Medal of the Institution of the Rubber Industry, the Witco Award in Polymer Chemistry of the American Chemical Society, the Technical Award of the International Institute of Synthetic Rubber Producers, and the Charles Goodyear Medal of the Rubber Division of the American Chemical Society. He has aided the scientific community in various capacities, including Chairman of the Committee on Macromolecular Chemistry of the National Research Council, President of the Society of Rheology, joint editor of the distinguished series Advances in Polymer Science and editorial board member for five journals. He supervised more than fifty graduate students, and had more than 30 postdoctoral and foreign associates from 17 foreign countries working in his laboratories at Wisconsin. More detailed and complete accounts of his many scientific contributions are found in references A, B and C, two summary papers written by John himself (references D and E), and in the three editions of his book.
John Ferry is equally well known and appreciated for attributes other than his scientific abilities and contributions. He is a true gentleman, a dedicated teacher and mentor who always has a genuine and abiding interest in and concern for all of his former students and collaborators. His gentle, patient and quiet personality has had a profound effect on all of us that have been privileged to know and work with him. His reputation for absolute integrity and his uncanny ability to emphasize and encourage the best in other individuals are attributes to which we all should aspire. He is a warm, unassuming, and dedicated person who also happens to be one of our most distinguished polymer scientists. Former students and associates have many fond memories of times spent at the Ferry home with John and his charming and vivacious wife Barbara, a former chemist turned artist, probably best known for her elegant sculptures.
The rheology and polymer science communities, to which John has been friend, mentor, colleague and exemplar, join together on this memorable occasion to wish him the best of health and happiness in the years ahead.
John L. Schrag
Department of Chemistry and Rheology Research Center
University of Wisconsin-Madison
Robert F. Landel
Jet Propulsion Lab
California Institute of Technology (retired)
A. J.L. Schrag, "John D. Ferry, Charles Goodyear Medalist - 1981: Biography," Rubber Chem. Tech., 54, G72-75 (1981).
B. R.F. Landel, "Professor John D. Ferry," J. Polymer Science, Physics Edition, 21. (1983).
C. N.W. Tschoegl, "John D. Ferry," Macromolecules, 20, 909 (1987).
D. J.D. Ferry, "Macromolecular Science, Retrospect and Prospect," in "Contemporary Topics in Polymer Science," Vol. 1, R.D. Ulrich, ed., pp 63- 68, Plenum Publ. Corp., New York (1978).
E. J.D. Ferry, "Probing Macromolecular Motions Through Viscoelasticity," Rubber Chem. Tech. 54, G 72-82 (1981) (The Goodyear Medal address).
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