Molecular models of synthetic rubber compounds, 20th century.
© Science Museum / Science & Society Picture Library
Two models showing the molecular structure of the basic unit (which is repeated many times) of a synthetic rubber containing fluorine (above) and silicon (below). Germany produced the first commercially succesful synthetic rubber, by co-polymerising two simpler substances. Buna-S was produced from butadiene and styrene, and Buna-N from butadiene and acrylonitrile. In the United States butyl rubber was produced by polymerising isobutylene, and neoprene from chloroprene. These latter two substances are examples of the proces of addition polymerisation, where simple units (monomers) are aded together to form a long chain molecule, rather than combining two substances together to produce a new compound.