Paul Flory
Encyclopedia
Paul John Flory was an American chemist and Nobel laureate who was known for his prodigious volume of work in the field of polymers, or macromolecules. He was a leading pioneer in understanding the behavior of polymer
s in solution, and won the Nobel Prize in Chemistry
in 1974 "for his fundamental achievements, both theoretical and experimental, in the physical chemistry of macromolecules."
in 1927, Flory received a bachelor's degree from Manchester College (Indiana) in 1931 and a Ph.D. from the Ohio State University
in 1934. His first position was at DuPont
with Wallace Carothers
.
kinetics
at the DuPont Experimental station. In condensation 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. In addition polymerization
, he introduced the important concept of chain 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 the University 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 or gels.
In 1940 he joined the Linden, NJ laboratory of the Standard Oil
Development Company where he developed a statistical mechanical theory for polymer mixtures. In 1943 he left to join the research laboratories of Goodyear
as head of a group on polymer fundamentals. In the Spring of 1948 Peter Debye
, then chairman of the chemistry department at Cornell 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. There he elaborated and refined his Baker Lectures into his magnum opus, Principles of Polymer Chemistry which was published in 1953 by Cornell 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 of excluded volume
, coined by Werner 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 the theta 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, the Flory-Huggins Solution Theory
, and the derivation of the Flory exponent, which helps characterize the movement of polymers in solution.
In modeling the position vectors of atoms in macromolecules it is often necessary to convert from Cartesian coordinates (x,y,z) to generalized 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 the bond length
s
, bond angles 
, and the dihedral angle
s
. Applying a vector conversion from the Cartesian coordinates to the generalized coordinates will describe the same three-dimensional structure using the Flory convention.
in 1974 "for his fundamental achievements, both theoretical and experimental, in the physical chemistry of macromolecules." He remained active after his retirement, and consulted for IBM
for some years. He and his wife Emily Catherine Tabor (now deceased) had three children, Susan, Melinda and John. Susan has two children, Elizabeth and Mary. Elizabeth has three children, Katy Greer, Margaret Greer, and Sam Greer. Paul J Flory died of a heart attack in Big Sur, California in 1985.
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s in solution, and won the Nobel Prize in Chemistry
Nobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...
in 1974 "for his fundamental achievements, both theoretical and experimental, in the physical chemistry of macromolecules."
Early life
After graduating from Elgin High School in Elgin, IllinoisElgin, Illinois
Elgin is a city in northern Illinois located roughly northwest of Chicago on the Fox River. Most of Elgin lies within Kane County, Illinois, with a portion in Cook County, Illinois...
in 1927, Flory received a bachelor's degree from Manchester College (Indiana) in 1931 and a Ph.D. from the Ohio State University
Ohio State University
The Ohio State University, commonly referred to as Ohio State, is a public research university located in Columbus, Ohio. It was originally founded in 1870 as a land-grant university and is currently the third largest university campus in the United States...
in 1934. His first position was at DuPont
DuPont
E. I. du Pont de Nemours and Company , commonly referred to as DuPont, is an American chemical company that was founded in July 1802 as a gunpowder mill by Eleuthère Irénée du Pont. DuPont was the world's third largest chemical company based on market capitalization and ninth based on revenue in 2009...
with Wallace Carothers
Wallace Carothers
Wallace Hume Carothers was an American chemist, inventor and the leader of organic chemistry at DuPont, credited with the invention of nylon....
.
Polymer science
Flory's earliest work in polymer science was in the area of polymerizationPolymerization
In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
kinetics
Chemical kinetics
Chemical kinetics, also known as reaction kinetics, is the study of rates of chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition...
at the DuPont Experimental station. In condensation 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. In addition polymerization
Addition polymerization
Chain growth polymerization is a polymerization technique where unsaturated monomer molecules add on to a growing polymer chain one at a time...
, he introduced the important concept of chain transfer
Chain transfer
Chain transfer is a polymerization reaction by which the activity of a growing polymer chain is transferred to another molecule.Chain transfer reactions reduce the average molecular weight of the final polymer...
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 the University of Cincinnati
University of Cincinnati
The University of Cincinnati is a comprehensive public research university in Cincinnati, Ohio, and a part of the University System of Ohio....
. There he developed a mathematical theory for the polymerization of compounds with more than two functional groups and the theory of polymer networks or gels.
In 1940 he joined the Linden, NJ laboratory of the Standard Oil
Standard Oil
Standard Oil was a predominant American integrated oil producing, transporting, refining, and marketing company. Established in 1870 as a corporation in Ohio, it was the largest oil refiner in the world and operated as a major company trust and was one of the world's first and largest multinational...
Development Company where he developed a statistical mechanical theory for polymer mixtures. In 1943 he left to join the research laboratories of Goodyear
Goodyear Tire and Rubber Company
The Goodyear Tire & Rubber Company was founded in 1898 by Frank Seiberling. Goodyear manufactures tires for automobiles, commercial trucks, light trucks, SUVs, race cars, airplanes, farm equipment and heavy earth-mover machinery....
as head of a group on polymer fundamentals. In the Spring of 1948 Peter Debye
Peter Debye
Peter Joseph William Debye FRS was a Dutch physicist and physical chemist, and Nobel laureate in Chemistry.-Early life:...
, then chairman of the chemistry department at Cornell University
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
, invited Flory to give the annual Baker Lectures. He then was offered a position with the faculty in the Fall of the same year. There he elaborated and refined his Baker Lectures into his magnum opus, Principles of Polymer Chemistry which was published in 1953 by Cornell 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 of excluded volume
Excluded volume
The concept of excluded volume was introduced by Werner Kuhn in 1934 and applied to polymer molecules shortly thereafter by Paul Flory.- In liquid state theory :...
, coined by Werner Kuhn
Werner Kuhn
Werner Kuhn is a Swiss physical chemist who developed the first model of the viscosity of polymer solutions using statistical mechanics. He is known for being the first to apply Boltzmann's entropy formula:S = k \log W \!...
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 the theta point
Theta solvent
In a polymer solution, a theta solvent is a solvent in which polymer coils act like ideal chains, assuming exactly their random walk coil dimensions...
, 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, the Flory-Huggins Solution Theory
Flory-Huggins solution theory
Flory-Huggins solution theory is a mathematical model of the thermodynamics of polymer solutions which takes account of the great dissimilarity in molecular sizes in adapting the usual expression for the entropy of mixing. The result is an equation for the Gibbs free energy change \Delta G_m for...
, and the derivation of the Flory exponent, which helps characterize the movement of polymers in solution.
The Flory convention
- see Flory conventionFlory conventionThe Flory convention for defining the variables involved on modeling the position vectors of atoms in macromolecules it is often necessary to convert from Cartesian coordinates to generalized coordinates...
for details.
In modeling the position vectors of atoms in macromolecules it is often necessary to convert from Cartesian coordinates (x,y,z) to generalized coordinates
Generalized coordinates
In the study of multibody systems, generalized coordinates are a set of coordinates used to describe the configuration of a system relative to some reference configuration....
. 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 the bond length
Bond length
- Explanation :Bond length is related to bond order, when more electrons participate in bond formation the bond will get shorter. Bond length is also inversely related to bond strength and the bond dissociation energy, as a stronger bond will be shorter...
s
, bond angles , and the dihedral angleDihedral angle
In geometry, a dihedral or torsion angle is the angle between two planes.The dihedral angle of two planes can be seen by looking at the planes "edge on", i.e., along their line of intersection...
s
. Applying a vector conversion from the Cartesian coordinates to the generalized coordinates will describe the same three-dimensional structure using the Flory convention.Later years
He accepted a professorship at Stanford University in 1961, became the Jackson-Wood Professor there in 1966 and retired from there in 1975. He was awarded the Nobel Prize in ChemistryNobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...
in 1974 "for his fundamental achievements, both theoretical and experimental, in the physical chemistry of macromolecules." He remained active after his retirement, and consulted for IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
for some years. He and his wife Emily Catherine Tabor (now deceased) had three children, Susan, Melinda and John. Susan has two children, Elizabeth and Mary. Elizabeth has three children, Katy Greer, Margaret Greer, and Sam Greer. Paul J Flory died of a heart attack in Big Sur, California in 1985.