Chemistry Reference
In-Depth Information
The second aspect was based on the well-known fact that 15-17 membered
cyclic ketones which were difficult to prepare at that time possess a strong musk
odor.
A new synthetic approach was elaborated, namely the depolymerization of low
molar mass polyesters in vacuum at temperatures above 230 C. The catalysts
were optimized for different types of polyesters, and finally more than 60 new
cyclic monomers and dimer were isolated. Correlations between chemical struc-
ture and ring size, on the one hand, and yields, Tm's, density or odor, on the other,
were elaborated. For several macrocyclic esters consisting of 15-17 atoms in the
ring musk-like odors were indeed found.
The same synthetic approach was used for the preparation of cyclic anhydrides
[
39
-
43
]. It was known before that succinic and glutaric acid form cyclic anhy-
drides which do not polymerize (see Formula
3.1
, bottom). Hill and Carothers
studied the reactions of higher dicarboxylic acids with acetyl chloride or acetic
anhydride. In all cases, polymeric anhydrides were obtained which were supposed
to possess mixed anhydride end groups containing acetyl residues. The sensitivity
to hydrolysis alcoholysis and phenolysis prevented exact molar mass measure-
ments. However, a reliable distinction from monomeric cyclic anhydrides was
achieved by reaction with aniline, because cyclic anhydrides can only yield one
reaction product. When the polymeric anhydrides were heated to 150 C in vac-
uum they degraded almost completely by ''back-biting''. In this way 10 new cyclic
anhydrides were isolated. These cyclic anhydrides underwent rapid polymerization
in contact with traces of moisture.
A systematic exploration of aliphatic polyamides was launched in 1934. W.R.
Peterson, D. Coffman, and (later) G. Berchet were the active researchers in this
field. After several fiber-forming and high-melting polyamides were obtained in
small scale experiments, K. Bolton decided to concentrate all further efforts on the
polyamide later called Nylon-6,6. For the development of a commercial textile
fiber, a new team was installed with G. Graves as leader. In 1935 the first pound of
nylon-6.6 was prepared and used for fundamental studies of fiber spinning. The
technical production began in 1938, and in 1939 and 1940 a worldwide PR-
campaign for the first man-made fiber was launched. Nylon stockings for women
was the first commercial hit. Yet, under the influence of World War II most of
DuPont's Nylon production was reserved for military purposes, above all for the
production of parachutes. In both areas, stockings and parachutes, the Nylon fiber
replaced the silk which was imported before from Japan. After World War II the
success story of Nylon-6,6 continued, although it was finally found that it is not an
ideal textile fiber for everyday clothes. However, it is an ideal fiber for any sport
activities and in the twenty-first century the most important application was the
production of carpets.
If Bolton's decision to select G. Graves as leader of the Nylon project was a
serious disappointment for Carothers or a relief is seemingly not clear. It had at
least two advantages for him, he could continue to concentrate on fundamental
research and he had less stress in his private life. Carothers was well aware of the
fact that he suffered from depressive moods. In 1931 he moved to a house in
