|Table of Contents for Caveman Chemistry: 28 Projects, from the Creation of Fire to the Production of Plastics|
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When you were in Cambridge this summer you referred to your interest in polymerization. I have some appreciation of the commercial importance of this subject because rubber, cellulose and its derivatives, resins and gums, and proteins may all be classified as large or polymerized molecules. This is a class of substances about which relatively little is known in terms of structure. None of these substances is very amenable to the classical tools of the organic chemist, and no doubt some of the most important contributions in this field will be made by experts in colloidal chemistry. From the standpoint of organic chemistry one of the first problems is to find out what is the size of these molecules and whether the forces involved in holding together the different units are of the same kind as those which operate in holding the atoms in ethyl alcohol together, or whether some other kind of valence is involved—more or less peculiar to highly polymerized substances.
For some time I have been hoping that it might be possible to tackle this problem from the synthetic side. The idea would be to build up some very large molecules by simple and definite reactions in such away that there could be no doubt as to their structures. This idea is no doubt a little fantastic and one might run up against insuperable difficulties. The point is that if it were possible to build up a molecule containing 300 or 400 carbon atoms and having a definitely known structure, one could study its properties and find out to what extent they compare with polymeric substances. The bearing of this isn't restricted to rubber but is common to it and such other materials as cellulose, etc.
I just want to say one word. Plastics! There's a great future in plastics. It all started in 1845 when a German chemistry professor named Christian Schönbein treated cotton with nitric and sulfuric acids; the result was nitrocellulose, a material that could be molded into just about any shape a body could want. Folks had been using the word plastic since God was a child to describe clay and other such things that could be pressed into shape and it made sense to use the same word to describe this new moldable stuff. Schönbein wrote to Michael Faraday to describe all the cool stuff he was able to make out of it. Well, ten years later news of this cool stuff inspired Alexander Parkes to commercialize the production of nitrocellulose plastics, producing combs and shirt collars and whatnot. From Britain, nitrocellulose crossed the Atlantic, spider-fashion, landing in John Wesley Hyatt, an American who had invented a new way to make dominoes and dice. Billiard balls were next on his list of things to improve and because ivory was expensive, he figured that nitrocellulose might be just the thing. In 1868 he discovered that if you mixed nitrocellulose with camphor (a wood tar), you got a nifty ivory substitute, which he named celluloid, on account of it came from cellulose. Twelve years later, George Eastman came out with celluloid photographic film and in 1891 the first commercial motion picture was produced by none other than the inventor of the electric light bulb, Thomas Edison.
Edison, Edison, Edison. Everybody remembers Edison as the inventor of the light bulb as if he were the only person to succeed in producing one. Nobody remembers that Joseph Swan patiently worked on the light bulb for thirty years. Nobody remembers that he demonstrated a working carbon filament bulb in December of 1878. Nobody remembers that Edison lost his 1882 patent infringement suit against Swan. Nobody remembers that the two inventors went into business as the Edison and Swan Electric Light Company. Nobody remembers that Swan improved the light bulb filament by extruding a solution of nitrocellulose to produce the first artificial fiber. Nitrocellulose would make its mark as the first artificial silk substitute, but its extreme flammability made it less than ideal as a textile. Continuing the quest for perfect light bulb filament, Edward Weston dissolved cotton in ammoniacal copper hydroxide producing cupprammonium rayon. And by a curious coincidence Charles Cross and Edward Bevan were seeking the Holy Grail of light bulb filaments when they invented viscose rayon and cellulose acetate. In 1910 Henri and Camille Dreyfus of Celanese Corporation began manufacturing cellulose acetate film for those who did not appreciate the tendency of nitrocellulose movie film to go up in smoke.
I beg your pardon. Eastman's celluloid film may have been flammable, but at least it was smokeless. A century before the invention of acetate film Irénée du Pont de Nemours had immigrated to the United States to avoid the aftermath of the French Revolution. Having apprenticed under Lavoisier, du Pont was well-versed in the manufacture of gunpowder and, finding that American gunpowder was both expensive and sub-standard, he constructed a gunpowder mill in 1802. Demand for gunpowder increased dramatically throughout the nineteenth century as mining operations marched across the North American continent. The wars of that century were also a boon to powder manufacturers; the du Pont de Nemours Powder Company (DuPont) supplied powder to both sides in the Crimean war and provided one third of the explosives used by the United States during the Civil War. After the war, DuPont began to explore explosives based on nitroglycerin and nitrocellulose. To circumvent Alfred Nobel's dynamite patents, DuPont bought the California Powder Company in 1876. California Powder produced a mixture of nitroglycerin, sugar, and saltpeter called "White Hercules." At the close of the nineteenth century DuPont moved into nitrocellulose-based "smokeless powder" and held a monopoly in its supply to the US military.
Monopoly was DuPont's favorite game, as a matter of fact. By 1881 the Gunpowder Trade Association, or "Powder Trust" controlled 85% of the US gunpowder market and DuPont controlled the trust. Then in 1907 DuPont became the target of an anti-trust suit, the first of many, which discouraged its erstwhile practice of growth through the acquisition of its competition. In 1913 DuPont was broken up into the Hercules Powder Company, the Atlas Powder Company, and the du Pont de Nemours Powder Company. Hercules and Atlas were to compete with DuPont in dynamite and black powder; DuPont managed to hold on as the sole provider of smokeless powder to the US military. With plenty of cash from World War I ammunition sales, DuPont looked for expansion opportunities which would provide a peace-time outlet for nitrocellulose without setting off an anti-trust inquisition. In 1915 DuPont bought the Arlington Company, the largest American producer of celluloid and celluloid products, and two years later it acquired Harrison Brothers, a firm specializing in paints, pigments, and chemicals. DuPont developed a tough nitrocellulose automotive enamel, trademarked "Duco," which General Motors adopted in 1922 as a colorful alternative to Ford's basic black. From nitrocellulose enamel, DuPont moved into other cellulose products, notably viscose rayon, cellophane, and acetate film. In 1924 DuPont began manufacturing synthetic ammonia (from air), ending its dependence on imported nitrates as a source of essential nitric acid. DuPont was fast becoming a diversified chemical giant; by 1933 90% of its earnings would come from chemicals other than explosives.
It was for such a company that I, Wallace Hume Carothers, went to work in 1928. I was the egghead kid everyone made fun of in school—glasses, pocket protector, the whole shebang. My father sent me to study accounting at junior college despite my interest in science. With the depression on, I managed to land a job teaching business at Tarkio College, where I was able to take chemistry classes on the side. I soon found that my happiest times were when I was left alone in the lab. For the unhappy times I was comforted by a small vial of cyanide I kept on my watch chain. It was my little secret. Hoping to make something of myself, I enrolled in the graduate chemistry program at the University of Illinois. After graduation, Harvard gave me a job teaching chemistry, but I was a nervous lecturer and longed to be left alone with my research, my record player, and the odd bottle of beer. I soon accepted a position as head of research at DuPont, hoping that without the distractions of teaching I could finally succeed in doing something important with my life. And if I couldn't do something important, there was always my little secret.
Lighten up, man, you're creeping me out. Illinois Ph.D., Harvard professor, DuPont bigwig, what more could you want out of life?
The world was changing and I wanted to make a contribution. Most of the history of chemical industry had involved breaking big molecules down into smaller ones; this is what destructive distillation is all about. But chemists were just beginning to combine small molecules into big ones. In 1906 Leo Baekeland had introduced the plastic Bakelite, a polymer of phenol and formaldehyde. Julius Nieuwland had succeeded in polymerizing acetylene in 1925 and DuPont had licensed the process. My research team followed this up by reacting vinylacetyene with hydrogen chloride to form the monomer, 2-chlorobutadiene. This small molecule polymerizes into an elastic material, trademarked Neoprene by DuPont in 1933. Neoprene was more resistant to petroleum distillates than natural rubber, but the depressed price of natural rubber made neoprene too expensive for practical use.
What about polyester?
What about it? Nobody at the time knew what held polymers together. Some supposed that polymers were simply loose aggregations of smaller molecules; others believed that these smaller molecules were chemically bonded to one another. It seemed to me that if it were possible to build long chains of short molecules using known chemical reactions, and if the properties of these long chains were similar to those of natural polymers, these observations would support the "chemically bonded" hypothesis of polymer structure. It was my one good idea. To this end, my group began studying the condensation of acids and alcohols to produce esters, the same reaction that produces ethyl acetate from ethanol and acetic acid. We began our work on these polyesters by reacting ortho-phthalic acid, a molecule with two acid groups, and ethylene glycol, a molecule with two alcohol groups. We produced some interesting fibers but their melting point was too low to be useful as a textile. We gave up on it in 1930, but thanks for bringing it up.
Stop your whining. The rayons had been merely artificial fibers derived from natural cellulose. Your polyethylene orthophthalate was the first truly synthetic fiber, one whose starting materials were not polymers to begin with.
Since the polyesters had not worked out, we started on polyamides. We tried many acids and amines derived from petrochemicals, but the 6-carbon adipic acid and the 6-carbon hexamethylene diamine seemed to work out the best and DuPont trademarked this polymer as Nylon. Even so, I was unhappy. Perkin had invented mauve before the age of twenty; Hall and Héroult had invented electrolytic aluminum when they were both twenty-three; Davy had discovered three elements by the time he was thirty-two. At forty-one I had had only one good idea and I feared that I would never have a second one. I spent my days churning out too many corporate reports and my nights knocking down too many bottles of beer. As a mortal I had kept my little vial of cyanide a secret, but in 1937 that particular secret would no longer be kept. Hello Darkness, my old friend.
Unbelievable! You had everything to live for.
Quite the contrary, Figment; he had nothing to live for. He had had his one great I-dea and it no longer needed him. Spreading through the scientific literature and the corporate culture, it had taken on a life of its own. So when no hope was left in sight on that starry, starry night, he took his life as watery chemists seem to do.
Well, if he had stuck around he would have seen Nylon become DuPont's single largest source of income in the fifties and sixties. His polyester recipe would be modified slightly to produce polyethylene terephthalate, trademarked by DuPont as Dacron polyester. DuPont would enter the twenty-first century as the Earth's second largest producer of "better things for better living through chemistry."
Reference , p. 143.
Reference , July 29, 2002, p. 16.