Wallace Carothers deserves a double credit in the history of polymers
since not only did his team at DuPont develop the first commercial
synthetic elastomer, which is still commercially and technically
important today, but also, a few years later, he was responsible
for the discovery of arguably one of the greatest families of plastics
He was born on April 27th 1896, the eldest of four children, in
Burlington, Ohio. He was considered ‘bookish’ at school
but that was to underestimate his breadth of interests. As well
as devouring every book he could get hold of he was fascinated by
mechanical toys and he loved music, his tastes ranging from Bach
to Gilbert and Sullivan. In high school his interests turned to
chemistry and he built a laboratory in his bedroom.
His father taught at Capital City Commercial College in Des Moines
and it was here that Carothers went to study accounting when he
left school. He then moved to Tarkio College in Missouri to study
chemistry although, being short of funds, he used his accounting
learning to advantage by teaching it in his spare time! He must
have been a remarkable student – possibly unique - because
he was made head of the chemistry department WHILST STILL AN UNDERGRADUATE.
He graduated in 1920, obtained his Masters in 1921 and his Doctorate
from the University of Illinois in 1924. He was then appointed a
professor at Harvard where he began his serious research career
into high polymers.
It was during his time in Illinois that the tormented side of Carothers’
character surfaced when he filled a phial with cyanide, to be carried
with him for the rest of his life as an escape route if his fits
of depression became too much to bear.
In 1928 DuPont broke new ground by setting aside a laboratory for
pure research. The ‘Blue Skies’ approach is not unusual
today but at that time corporate research was very much ‘cashflow
oriented’. The chance to forgo teaching and devote all his
time to research was not to be missed and, at 32, he was placed
in charge of DuPont’s research division. It was known that
he suffered from moods of deep depression and his staff was warned
to look out for them but his mentor, Roger Adams, believed that
these could be controlled and that Carothers had much to give the
world from his researches. He was half right!
Dupont was aware of the work of Father Julius Nieuwland into the
synthesis of chloroprene from acetylene and believed that this could
be the precursor of a viable synthetic elastomer (chloroprene has
a molecular structure which can be described as that of isoprene
[the building block of natural rubber] with its branched methyl
group replaced by a chlorine atom). This became Carothers’
first project and in April 1930 the polymer was synthesised by one
of his team, Arnold Collins. This had the anticipated ‘rubbery’
properties and whilst these were somewhat poorer than those exhibited
by natural rubber in many areas it had a much greater oil resistance.
This gave it a niche market and it went into production in 1931
as Neoprene, the first commercially successful synthetic polymer
which is still in production today. The chemical name for the elastomer
is polychloroprene, Neoprene being DuPont’s trade name, but,
like Hoover, the word has now been accepted as generic.
With that problem quickly resolved (three years from start of research
to commercial production!) Carothers’ group turned its attention
to synthetic fibres, specifically to find a replacement for silk
which was in short supply because of trade and political problems
between the USA and Japan.
He had postulated some years earlier that if an acid and alcohol
could condense, with the elimination of water, to produce an ester,
it should be possible to make a giant molecule (polymer) by linking
diols to diesters. This was soon achieved by one of his team, Julian
Hill, to give an early polyester but the physical properties were
too poor for commercialisation and Carothers turned his attentions
to polyamides, replacing the diols with diamines. In 1934 the first
successful fibres were made. Carothers’ team was working with
over 100 different materials and he identified them by two numbers,
indicating the number of carbon atoms in the diacid and diamine.
In February 1935 he polymerised adipic acid (C6) and hexamethylene
diamine (C6) to give specimen 66 which had good physical properties
when it was drawn into a fibre. The material was christened Tiber
66 and, in September 1938 re-christened Nylon66. In three years
of research Carothers’ team had created the first commercial
synthetic rubber with the discovery of neoprene and now they had
done it in the plastics field with nylon.
Carothers’ immediate superior decided to hit one market with
this new product and in May 1940 nylon stockings hit the hosiery
stores nationwide. At just over one dollar a pair, five million
pairs were sold on the first day. When the States entered the Second
World War and arrived in the UK, a few pairs of nylons could buy
anything! By that time however, production of nylon had been directed
towards the war effort, particularly parachute canopies, rot-proof
cords and life rafts and the ladies had to wait a few more years
to have an unlimited supply of seamless or fully fashioned nylon
The research work of Carothers and his team changed the world but
he couldn’t cope with it even as it was and he never knew
what he had achieved. His earlier bouts of depression and heavy
drinking had destabilised him. He grew up in a very close relationship
with his sister, Isobel, and then fell in love with a married woman
but, when she became available, he retreated to his parents’
house. He spent time in a psychiatric hospital and was advised to
marry by his doctor.
In January 1936 his sister died and soon after he married Helen
Sweetman, a co-worker at DuPont. She and DuPont rapidly agreed that
he needed hospitalisation and after some treatment he was released
to take a walking holiday in the Alps with his old friend Roger
Adams. According to Adams he seemed to improve during this time
but relapsed on his return to the US even though he was actively
cared for by his wife, psychiatrist, friends and colleagues. In
the middle of April 1937 Helen told him that she was pregnant and
on April 29th of that year, alone in a hotel in Philadelphia, he
cracked open his phial of cyanide and died believing that he was
‘morally bankrupt’ and that his work had been useless.
Helen later gave birth to a daughter, Jane.