5th Solvay Conference on Chemistry, 1934

When chemists began looking more closely at rubber, it appeared that establishing its chemical structure was very difficult. Since the second half of the nineteenth century, other substances such as gum, tar, gelatine or starch have seemed to resist the laws of organic chemistry. Organic chemistry then defined a group of ‘well-behaved’ molecules with a molar mass below 5,000 g/mol and which crystallize, have set melting and boiling points, and a univocal formula. By contrast, the others are called colloids and, among the chemists studying them, Hermann Staudinger (1881–1965) proposed the term of ‘macromolecules’ in 1922, a term that has now been adopted in chemistry. But it would take a long time before colloid chemists and later the whole community accepted this idea. Indeed, other hypotheses existed: among others, these could be aggregates of shorter molecules joined together by bonds weaker than valence bonds. During the 1934 Conference on Chemistry, chemists are invited to discuss organic molecules and Staudinger presents his theory which is hotly discussed, without any hypothesis gaining the upper hand, however. In 1953 he is awarded the Nobel Prize in Chemistry.