Paul John Flory (June 19, 1910 – September 9, 1985) was an American chemist andNobel laureate who was known for his work in the field ofpolymers, ormacromolecules.[2] He was a pioneer in understanding the behavior ofpolymers in solution, and won theNobel Prize in Chemistry in 1974 "for his fundamental achievements, both theoretical and experimental, in the physical chemistry of macromolecules".[3]
Flory was born in Sterling, Illinois, on June 19, 1910 to Ezra Flory and Martha Brumbaugh. His father worked as a clergyman-educator, and his mother was a school teacher. His ancestors wereGermanHuguenots, who traced their roots back toAlsace.[4][5] He first gained an interest in science from Carl W Holl, who was a chemistry professor atManchester College. In 1936, he married Emily Catherine Tabor. They had three children together: Susan Springer, Melinda Groom and Paul John Flory, Jr. His first position was atDuPont withWallace Carothers.[6][7] He was posthumously inducted into theAlpha Chi Sigma Hall of Fame in 2002.[8] Flory died on September 9, 1985, following a heart attack.[9] His wife Emily died in 2006 aged 94.
After graduating fromElgin High School in 1927, Flory received a bachelor's degree from Manchester College (now Manchester University (Indiana) in 1931 and a Ph.D. from theOhio State University in 1934. He completed a years of master's study in organic chemistry under the supervision of Prof. Cecil E Boord,[10] before moving into physical chemistry. Flory's doctoral thesis was on the photochemistry of nitric oxide, supervised by Prof. Herrick L. Johnston.[11]
In 1934 Flory joined the Central Department ofDupont and Company working withWallace H. Carothers.[11] After Carothers' death in 1937, Flory worked for two years at the Basic Research Laboratory located in the University of Cincinnati. During World War II, there was a need for research to develop synthetic rubber, so Flory joined the Esso Laboratories of theStandard Oil Development Company.[10] From 1943 to 1948 Flory worked in the polymer research team of the Goodyear Tire and Rubber Company.[2]
In 1948, Flory gave the George Fisher Baker lectures atCornell University, and subsequently joined the university as a professor.[2] In 1957, Flory and his family moved to Pittsburgh, Pennsylvania, where Flory was executive director of research at theMellon Institute of Industrial Research.[2] In 1961, he took up a professorship atStanford University in the department of chemistry. After retirement, Flory remained active in the world of chemistry, running research labs both in Stanford, and IBM.[2]
Flory's earliest work in polymer science was in the area ofpolymerizationkinetics at theDuPont Experimental Station. Incondensation polymerization, he challenged the assumption that the reactivity of the end group decreased as the macromolecule grew, and by arguing that the reactivity was independent of the size, he was able to derive the result that the number of chains present decreased with size exponentially. Inaddition polymerization, he introduced the important concept ofchain transfer to improve the kinetic equations and remove difficulties in understanding the polymer size distribution.
In 1938, after Carothers' death, Flory moved to the Basic Science Research Laboratory at theUniversity of Cincinnati. There he developed a mathematical theory for the polymerization of compounds with more than two functional groups and the theory of polymer networks orgels. This led to theFlory-Stockmayer theory of gelation, which was equivalent topercolation on theBethe lattice and represents the first paper in the percolation field.
In 1940 he joined theLinden, NJ laboratory of theStandard Oil Development Company where he developed a statistical mechanical theory for polymer mixtures. In 1943 he left to join the research laboratories ofGoodyear as head of a group on polymer fundamentals. In the Spring of 1948Peter Debye, then chairman of the chemistry department atCornell University, invited Flory to give the annual Baker Lectures. He then was offered a position with the faculty in the Fall of the same year. He was initiated into the Tau chapter ofAlpha Chi Sigma at Cornell in 1949.[8] At Cornell he elaborated and refined his Baker Lectures into his magnum opus,Principles of Polymer Chemistry which was published in 1953 byCornell University Press. This quickly became a standard text for all workers in the field of polymers, and is still widely used to this day.
Flory introduced the concept ofexcluded volume, coined byWerner Kuhn in 1934, to polymers. Excluded volume refers to the idea that one part of a long chain molecule can not occupy space that is already occupied by another part of the same molecule. Excluded volume causes the ends of a polymer chain in a solution to be further apart (on average) than they would be were there no excluded volume. The recognition that excluded volume was an important factor in analyzing long-chain molecules in solutions provided an important conceptual breakthrough, and led to the explanation of several puzzling experimental results of the day. It also led to the concept of thetheta point, the set of conditions at which an experiment can be conducted that causes the excluded volume effect to be neutralized. At the theta point, the chain reverts to ideal chain characteristics – the long-range interactions arising from excluded volume are eliminated, allowing the experimenter to more easily measure short-range features such as structural geometry, bond rotation potentials, and steric interactions between near-neighboring groups. Flory correctly identified that the chain dimension in polymer melts would have the size computed for a chain in ideal solution if excluded volume interactions were neutralized by experimenting at the theta point.
Among his accomplishments are an original method for computing the probable size of a polymer in good solution, theFlory-Huggins Solution Theory, the extension of polymer physics concepts to the field of liquid crystals, and the derivation of theFlory exponent, which helps characterize the movement of polymers in solution.[2]
In modeling the position vectors of atoms in macromolecules it is often necessary to convert fromCartesian coordinates (x,y,z) togeneralized coordinates. The Flory convention for defining the variables involved is usually employed. For an example, a peptide bond can be described by the x,y,z positions of every atom in this bond or the Flory convention can be used. Here one must know thebond lengths,bond angles, and thedihedral angles. Applying a vector conversion from the Cartesian coordinates to the generalized coordinates will describe the same three-dimensional structure using the Flory convention.
^"Paul J. Flory – Biographical".nobelprize.org. 1974. RetrievedJanuary 28, 2024.I was born on 19 June 1910, in Sterling, Illinois, of Huguenot-German parentage, mine being the sixth generation native to America.
^Johnson, William S.; Stockmayer, Walter H.; Taube, Henry (2002)."Paul John Flory 1910–1985"(PDF).Biographical Memoirs of the National Academy of Sciences: 4. RetrievedJanuary 28, 2024.The Flory family traces its roots back to Alsace, then England, later to Pennsylvania, and then to Ohio.
^Morris, Peter J. T. (1986)Polymer Pioneers: A Popular History of the Science and Technology of Large Molecules Center for History of Chemistry, Philadelphia. pp. 70–73.ISBN0941901033
