# Paul Flory

Paul John Flory (June 19 1910September 9 1985) was an American chemist who was known for his prodigious volume of work in the field of polymers, or macromolecules. After graduating from Elgin High School in Elgin, Illinois in 1927, Flory received a bachelor's degree from Manchester College in 1931 and a Ph.D. from Ohio State University in 1934. His first position was at DuPont with Wallace Carothers. He was a leading pioneer in understanding the behavior of polymers in solution. 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. He introduced the concept of excluded volume, which causes a polymer chain to be expanded in a good solution, and thus provided important conceptual breakthrough explaining several experimental results of the day. This also led to concept of theta point, condition at which the excluded volume is neutralized and chain reverts to ideal chain characteristics. He correctly identified that the chain dimension in polymer melts would have the size computed for a chain in ideal solution, as excluded volume interactions get screened.

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 to 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 lengths $l_i$, bond angles $\theta_i$, and the dihedral angles $\phi_i$. Applying a vector conversion from the Cartesian coordinates to the generalized coordinates will describe the same three dimensional structure using the Flory convention.

His contributions to the field of polymer science is best summarized in his classic 1953 text, Principles of Polymer Chemistry, where he provides a comprehensive account of experimental and theoretical results proven in his day. While the field of polymers has expanded considerably, the text continues to be highly useful in understanding several key concepts and for didactic reasons.

He was awarded the Nobel Prize in Chemistry in 1974.

## Books

• (1953) Principles of Polymer Chemistry (George Fisher Baker Non-Resident Lec). Cornell University Press. ISBN 0801401348.
• (1969) Statistical Mechanics of Chain Molecules. Interscience. ISBN 0470264950. Reissued 1989. ISBN 1569900191.
• (1985) Selected Works of Paul J. Flory. Stanford Univ Press. ISBN 0804712778.