Plastics
Modern life would be incomparably different without synthetic chemicals called polymers. Man-made fibres, as used in clothing, carpets and curtains, plastics used in innumerable domestic and industrial applications and artificial joints, and paints and cleaning materials, are all different forms of this important discovery. What s often forgotten is that at the beginning of the 20th century the chemistry of large molecules was unknown and their synthesis unthinkable.
Large Molecules
When a German scientist named Hermann Staudinger proposed in the 1920s that it was possible to have large molecules made up of many thousands of atoms, he was ridiculed by many other scientists. The common wisdom was that the structures of such materials as rubber and Bakelite were actually many small molecules held together by an unknown force.
Organic Synthesis
Staudinger stuck to his guns and, with his colleagues, he synthesised a series of organic molecules called poly(methanal)s. These compounds were long chains of repeating units, the units being -CH2O-. They are made by joining lots of methanal molecules together. The German scientists made chains of different lengths and showed that their properties changed depending on the length of the chains.
The next question to answer was: Are polymers any use? Chemists working for Imperial Chemical Industries (ICI), soon discovered a polymer which put the answer to this question beyond any doubt. They were attempting to react to organic molecules, ethylene (now known as ethene) and benzaldehyde, at very high temperature and pressure. The reaction failed to impress, but there was a small amount of a white, waxy substance on the wall of the reaction vessel. This was poly(ethene) or polythene, and soon ICI realised they had a potentially useful compound.
World War II
The new material had many properties which made it stand out. It was easy to form into different items, was tough and hard wearing, was impermeable to water and insulating to electricity. It was discovered in the 1930s and was soon being used in the Second World War to insulate the many metres of cables needed for the vital radar equipment used by the British.
HDPE
The development of the petrochemical industry after the war supplied the raw materials for this product. Then a catalysed method of producing high-density poly(ethene) (HDPE) was discovered by Karl Zeigler in Mülheim, Germany in 1950. Both these developments meant that the world would never be the same again as more and more uses for this plastic were discovered.
Nylon and Lycra
Soon other types of polymers were being developed. Some of the more important were poly(propene) by Giulio Natta in Milan, Nylon by Wallace Carothers in the US, poly(urethane)s, used in Lycra, and polyesters, a very important raw material for the clothing industry.
Future
The history of the development of polymers is nowhere near its end. New developments and advances are constantly being made and every year there are new patents for novel molecules which promise much. Only time will tell how we will come to depend even more on these compounds.
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