Page 342 - Carrahers_Polymer_Chemistry,_Eighth_Edition

Naturally Occurring Polymers—Plants 305

H C C CH CH 3
2
2
|
CH 3 (9.36)
Isoprene
Again, as noted above, with knowledge that NR had isoprene units, chemists worked to duplicate
the synthesis of rubber except using synthetic monomers. These attempts failed until two factors
were realized. First, after much effort it was discovered that the methyl groups were present in a
“cis” arrangement. Second, it was not until the discovery of stereoregular catalysts that the chemists
had the ability to form NR-like material from butadiene.
The search for the synthesis of a purely SR, structurally similar to NR, continued and involved a
number of scientists building upon one another’s work—along with a little creativity. Nieuwland, a
Catholic priest, President of Notre Dame University, and a chemist did extensive work on acetylene.
He found that acetylene could be made to add to itself forming dimers and trimers (Equation 9.37).

H C CH C H 2
C
H 2
C
H 2 CH 2
(9.37)
Acetylene Vinylacetylene Divinylacetylene
Calcott, a DuPont chemist, attempted to make polymers from acetylene, reasoning that if acet-
ylene formed dimers and trimers, conditions could be found to produce polymers. He failed, but
went to Carothers who had one of his chemists, Arnold Collins, work on the project. Collins ran the
reaction described by Nieuwland, purifying the reaction mixture. He found a small amount of mate-
rial that was not vinylacetylene or divinylacetylene. He set the liquid aside. When he came back,
the liquid had solidified giving a material that seemed rubbery and even bounced. They analyzed

the rubbery material and found that it was not a hydrocarbon, but it had chlorine in it. The chlorine
had come from HCl that was used in Nieuwland’s procedure to make the dimers and trimers. The
hydrogen chloride added to the vinylacetylene forming chloroprene.
This new rubber was given the name Neoprene (Equation 9.38). Neoprene had outstanding resistance
to gasoline, ozone, and oil in contrast to NR. Today, Neoprene is used in a variety of applications, includ-
ing as electrical cable jacketing, window gaskets, shoe soles, industrial hose, and heavy duty drive belts.
( CH
H C C CH CH 2 | | 2 C CH CH 2 ) |
2
|
|
|
|
| |
Cl Cl
(9.38)
Chloroprene Polychloroprene
(Neoprene)
Thiokol was developed by J. C. Patrick in 1926. Joseph Cecil Patrick was born in 1892 in Jefferson
County, MO. He was a physician rather than a chemist. Before completing his medical school stud-
ies, World War I began and he tried to join the U.S. Air Corps. Because of poor health, he could
not meet the standards for combat service but was accepted in the U.S. Medical Corps and was sent
to serve in France. While there, he was part of the influenza epidemic and was found in a coma

surrounded by corpses awaiting shipment for interment. His escape from burial may have been the
result of the administering of a large dose of quinine by a French nurse.
On returning to the United States he continued his medical education and accepted a position as a pub-
lic health inspector in Kansas City, MO. Within the year he took a better paying job as an analytical chem-
ist for Armor Packing Company in Buenos Aires, Argentina. He returned to the United States again, and
finally completed his medical training from the Kansas City College of Medicine and Surgery in 1922.

Rather than practicing medicine he helped establish the Industrial Testing Laboratory, Inc. in
Kansas City by the mid-1920s. He developed a process for the production of pectin as a precipitate
from apples from a vinegar plant.

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