Paul Flory

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Paul Flory

Paul Flory (1910-1985), founder of the science of polymers, was a researcher in macronuclear chemistry and was awarded the Nobel Prize in 1974.

Paul Flory is widely recognized as the founder of the science of polymers. The Nobel Prize in chemistry he received in 1974 was awarded not for any single specific discovery, but, more generally, "for his fundamental achievements, both theoretical and experimental, in the physical chemistry of macromolecules." That statement accurately reflects the wide-ranging character of Flory's career. He worked in both industrial and academic institutions and was interested equally in the theory of macromolecules and in the practical applications of that theory.

Paul John Flory was born in Sterling, Illinois, on June 19, 1910. His parents were Ezra Flory, a clergyman and educator, and Martha (Brumbaugh) Flory, a former school teacher. Ezra and Martha's ancestors were German, but they had resided in the United States for six generations. Both the Flory and the Brumbaugh families had always been farmers, and Paul's parents were the first in their line ever to have attended college.

After graduation from Elgin High School, Flory enrolled at his mother's alma mater, Manchester College, in North Manchester, Indiana. The college was small, with an enrollment of only 600. He earned his bachelor's degree in only three years, at least partly because the college "hadn't much more than three years to offer at the time," as he was quoted as having said by Richard J. Seltzer in Chemical and Engineering News. An important influence on Flory at Manchester was chemistry professor Carl W. Holl. Holl apparently convinced Flory to pursue a graduate program in chemistry. In June of 1931, therefore, Flory entered Ohio State University and, in spite of an inadequate background in mathematics and chemistry, earned his master's degree in organic chemistry in less than three months. He then began work immediately on a doctorate, but switched to the field of physical chemistry. He completed his research on the photochemistry of nitric oxide and was granted his Ph.D. in 1934.

Flory's doctoral advisor, Herrick L. Johnston, tried to convince him to stay on at Ohio State after graduation. Instead, however, he accepted a job at the chemical giant, Du Pont, as a research chemist. There he was assigned to a research team headed by Wallace H. Carothers, who was later to invent the process for making nylon and neoprene. Flory's opportunity to study polymers was ironic in that, prior to this job, he knew next to nothing about the subject. Having almost any job during the depths of the Great Depression was fortunate, and Flory was the envy of many classmates at Ohio State for having received the Du Pont offer.

Flory's work on the Carothers team placed him at the leading edge of chemical research. Chemists had only recently begun to unravel the structure of macromolecules, very large molecules with hundreds or thousands of atoms, and then to understand their relationship to polymers, molecules that have chemically combined to become a single, larger molecule. The study of polymers was even more difficult than that of macromolecules because, while the latter are very large in size, they have definite chemical compositions that are always the same for any one substance. Polymers, on the other hand, have variable size and composition. For example, polyethylene, a common polymer, can consist of anywhere from a few hundred to many thousands of the same basic unit (monomer), arranged always in a straight chain or with cross links between chains.

With his background in both organic and physical chemistry, Flory was the logical person to be assigned the responsibility of learning more about the physical structure of polymer molecules. That task was made more difficult by the variability of size and shape from one polymer molecule to another—even among those of the same substance. Flory's solution to this problem was to make use of statistical mechanics to average out the properties of different molecules. That technique had already been applied to polymers by the Swiss chemical physicist Werner Kuhn and two Austrian scientists, Herman Mark and Eugene Guth. But Flory really developed the method to its highest point in his research at Du Pont.

During his four years at Du Pont, Flory made a number of advances in the understanding of polymer structure and reactions. He made the rather surprising discovery, for example, that the rate at which polymers react chemically is not affected by the size of the molecules of which they are made. In 1937, he discovered that a growing polymeric chain is able to terminate its own growth and start a new chain by reacting with other molecules that are present in the reaction, such as those of the solvent. While working at Du Pont, Flory met and, on March 7, 1936, married Emily Catherine Tabor. The Florys had two daughters, Susan and Melinda, and a son, Paul John, Jr. Flory's work at Du Pont came to an unexpected halt when, during one of his periodic bouts of depression, Carothers committed suicide in 1937. Although deeply affected by the tragedy, Flory stayed on for another year before resigning to accept a job as research associate with the Basic Science Research Laboratory at the University of Cincinnati. His most important achievement there was the development of a theory that explains the process of gelation, which involves cross-linking in polymers to form a gel-like substance.

Flory's stay at the University of Cincinnati was relatively brief. Shortly after World War II began, he accepted an offer from the Esso (now Exxon) Laboratories of the Standard Oil Development Company to do research on rubber. It was apparent to many American chemists and government officials that the spread of war to the Pacific would imperil, if not totally cut off, the United States' supply of natural rubber. A massive crash program was initiated, therefore, to develop synthetic substitutes for natural rubber. Flory's approach was to learn enough information about the nature of rubber molecules to be able to predict in advance which synthetic products were likely to be good candidates as synthetic substitutes ("elastomers"). One result of this research was the discovery of a method by which the structure of polymers can be studied. Flory found that when polymers are immersed in a solvent, they tend to expand in such a way that, at some point, their molecular structure is relatively easy to observe.

In 1943, Flory was offered an opportunity to become the leader of a small team doing basic research on rubber at the Goodyear Tire and Rubber Company in Akron, Ohio. He accepted that offer and remained at Goodyear until 1948. One of his discoveries there was that irregularities in the molecular structure of rubber can significantly affect the tensile strength of the material.

In 1948, Flory was invited by Peter Debye, the chair of Cornell University's department of chemistry, to give the prestigious George Fisher Baker Lectures in Chemistry. Cornell and Flory were obviously well pleased with each other as a result of this experience, and when Debye offered him a regular appointment in the chemistry department beginning in the fall of 1948, Flory accepted—according to Maurice Morton in Rubber Chemistry and Technology—"without hesitation." The Baker Lectures he presented were compiled and published by Cornell University Press in 1953 as Principles of Polymer Chemistry. Flory continued his studies of polymers at Cornell and made two useful discoveries. One was that for each polymer solution there is some temperature at which the molecular structure of the polymer is most easily studied. Flory called that temperature the theta point, although it is now more widely known as the Flory temperature. Flory also refined a method developed earlier by the German chemist Hermann Staudinger to discover the configuration of polymer molecules using viscosity. Finally, in 1956, he published one of the first papers ever written on the subject of liquid crystals, a material ubiquitous in today's world, but one that was not to be developed in practice until more than a decade after Flory's paper was published.

In 1957, Flory became executive director of research at the Mellon Institute of Industrial Research in Pittsburgh. His charge at Mellon was to create and develop a program of basic research, a focus that had been absent from that institution, where applied research and development had always been of primary importance. The job was a demanding one involving the supervision of more than a hundred fellowships. Eventually, Flory realized that he disliked administrative work and was making little progress in refocusing Mellon on basic research. Thus, when offered the opportunity in 1961, he resigned from Mellon to accept a post at the department of chemistry at Stanford University. Five years later, he was appointed Stanford's first J. G. Jackson-C. J. Wood Professor of Chemistry. When he retired from Stanford in 1975, he was named J. G. Jackson-C. J. Wood Professor Emeritus. In 1974, a year before his official retirement, Flory won three of the highest awards given for chemistry—the National Medal of Science, the American Chemical Society's Priestley Medal, and the Nobel Prize in chemistry. These awards capped a career in which, as Seltzer pointed out, Flory had "won almost every major award in science and chemistry."

Flory's influence on the chemical profession extended far beyond his own research work. He was widely respected as an outstanding teacher who thoroughly enjoyed working with his graduate students. A number of his students later went on to take important positions in academic institutions and industrial organizations around the nation. His influence was also felt as a result of his two books, Principles of Polymer Chemistry, published in 1953, and Statistical Mechanics of Chain Molecules, published in 1969. Leo Mandelkern, a professor of chemistry at Florida State University, is quoted by Seltzer as referring to the former work as "the bible" in its field, while the latter has been translated into both Russian and Japanese.

Flory was also active in the political arena, especially after his retirement in 1975. He and his wife decided to use the prestige of the Nobel Prize to work in support of human rights, especially in the former Soviet Union and throughout Eastern Europe. He served on the Committee on Human Rights of the National Academy of Sciences from 1979 to 1984 and was a delegate to the 1980 Scientific Forum in Hamburg, at which the topic of human rights was discussed. As quoted by Seltzer, Morris Pripstein, chair of Scientists for Sakharov, Orlov, and Scharansky, described Flory as "very passionate on human rights…You could always count on him." At one point, Flory offered himself to the Soviet government as a hostage if it would allow Soviet scientist Andrei Sakharov's wife, Yelena Bonner, to come to the West for medical treatment. The Soviets declined the offer, but eventually did allow Bonner to receive the necessary treatment in Italy and the United States.

Flory led an active life with a special interest in swimming and golf. In the words of Ken A. Dill, professor of chemistry at the University of California, San Francisco, as quoted by Seltzer, Flory was "a warm and compassionate human being. He had a sense of life, a sense of humor, and a playful spirit. He was interested in, and cared deeply about, those around him. He did everything with a passion; he didn't do anything half way." Flory died on September 8, 1985, while working at his weekend home in Big Sur, California. According to Seltzer, at Flory's memorial service in Stanford, James Economy, chair of the American Chemical Society's division of polymer chemistry, expressed the view that Flory was "fortunate to depart from us while still at his peak, not having to suffer the vicissitudes of old age, and leaving us with a sharply etched memory of one of the major scientific contributors of the twentieth century."

Further Reading

Morton, Maurice, "Paul John Flory, 1910-1985, part I: The Physical Chemistry of Polymer Synthesis," in Rubber Chemistry and Technology, May-June, 1987, pp. G47-G57.

Seltzer, Richard J., "Paul Flory: A Giant Who Excelled in Many Roles," in Chemical and Engineering News, December 23, 1985, pp. 27-30. □

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