"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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