Paul Flory – pioneer in polymer science

Paul Flory [Paul John Flory], an American chemist and Nobel laureate born on June 19, 1910 – died on September 09, 1985. Paul studied the properties of polymers, chain conformation, crystallization, elasticity, glass formation, hydrodynamics, liquid crystals, melt viscosity, molar mass distribution, and solution thermodynamics.

In 1937, while working at DuPont under Wallace Hume Carothers, he discovered that a growing polymeric chain can terminate its growth and instead start a new chain, if it reacts with other molecules that are present.

In 1939 at the University of Cincinnati paul developed a theory of polymer networks to explain the process of gelation.

Paul Flory was awarded with various prestigious medals, awards in his life time like Elliott cresson medal in the year of 1971, Nobel Prize for physical chemistry works on macromolecules in the year of 1974, Priestley medal in the year of 1974, Perkin medal in the year of 1977.

Flory introduced the concept of 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.

In addition polymerization, flory introduced the important concept of chain transfer to improve the kinetic equations and remove difficulties in understanding the polymer size distribution. In condensation polymerization, flory 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.

Condensation polymerization

Condensation polymerization can be defined as it is a form of step-growth polymerization / it is a process by which two molecules join together, resulting loss of small molecules which is often water. The type of end product resulting from a condensation polymerization is dependent on the number of functional end groups of the monomer which can react. Condensation polymerization is occasionally used to form simple hydrocarbons.

Chain polymerization

Chain polymerization also termed as chain-growth polymerization. Chain polymerization is a polymerization technique where unsaturated monomer molecules add onto the active site on a growing polymer chain one at a time.

Examples

Reactions in Polyethylene, polypropylene, and polyvinyl chloride are all belongs to chain polymerizations.

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