University of Florida, Gainesville
Center for Macromolecular Science and Engineering - University of Florida Polymer Science Program

"Impossible" Discovery Creates a Legacy at UF

Dimethyldiallyl ammonium chloride, a nonconjugated diene, was under study to produce a cross-linked ion exchange resin for the Office of Naval Research. The research was intended to be rather conventional chemistry, which in fact sparked observations that defined a concept involving cyclization during the propagation event. No doubt, and as expected, the olefin unsaturation in the monomer was completely consumed during the polymerization; however, no crosslinking was observed whatsoever. In fact, the polymers were soluble in water!

Another pair of monomers, divinyl ether and maleic anhydride also gave unpredictable results. The experiment that eventually led to what is known as cyclocopolymerization was done on Thanksgiving Day in 1951, with no apparent connection to ion exchange resin research. The goal was to produce a crosslinked medicinal polymer for the treatment of high blood pressure. The result, instead, was a completely soluble polymer in basic aqueous solutions - again, an unbelievable result.

These results just were not supposed to be. In 1934 Staudinger reported that nonconjugated dienes lead to crosslinked polymers since such monomers are tetrafunctional under radical polymerizations. Of course, Staudinger is right in most cases, except when intramolecular reactions prove possible - in this case, the formation of a ring. In 1937 Flory showed that propagation in radical polymerization should proceed through the most stable reactive intermediate (a secondary free radial rather than a primary free radical in the case of cyclopolymerization chemistry). As a consequence, the cyclopolymerization of dimethyldiallyl ammonium chloride (the first monomer to be thoroughly investigated) should lead to the formation of a six-membered ring. In fact, five-membered rings are formed for kinetic reasons.

Thus was born the concept of intramolecular-intermolecular chain polymerization, now known everywhere in the world as cyclopolymerization and cyclocopolymerization.

It took several years to work out the mechanistic details, and even then the scientific community was skeptical of this novel polymerization scheme. For example, the work was submitted for presentation before the Organic Division of the American Chemical Society in 1955 but was turned down. In his rejection, the secretary of the Organic Division offered an alternate explanation of the observed results (he was wrong, of course). The paper eventually was accepted for the 1956 ACS meeting and has resulted in more than 4,500 publications in the field from scientists all over the world.

The chemistry created about 100 MS and PhD degrees at the University of Florida and initiated the formation of Peninsular Chemical Research, a startup company in Gainesville founded by Professor Butler and Professor Paul Tarrant. The company was immediately successful and produced commercial products that were sold everywhere for a variety of applications. First success was found in potable and wastewater treatment and purification, followed by applications in the paper and textile industry, the cosmetic and personal care field, in biological, medical and food applications, in membrane technology, and in agricultural and soil treatment.

The success continues today. Not only does cyclopolymerization continue to enjoy commercial and academic success, it spawned the Center for Macromolecular Science & Engineering at the University of Florida. We all are grateful for what Professor Butler started 60 years ago.

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