Über Polymerisation (On Polymerization)
Rubber, plastic and protein are each one giant molecule, not a heap of small ones.
For a century chemists assumed molecules came in one size: small. Staudinger insisted that some are gigantic — and that rubber, silk and plastic are each, in effect, one enormous molecule.
The big idea
Most molecules you meet in chemistry are tiny — a water molecule is just three atoms. Staudinger said that materials like rubber, cellulose and the early plastics are different in kind: each is built from thousands of small units locked end-to-end by strong chemical bonds into one immense chain molecule, what he later named a macromolecule. Stretched out, a single one might be tens of thousands of atoms long.
That sounds obvious now, but in 1920 it was heresy. The accepted explanation was that these substances were just lots of ordinary small molecules clinging together in clumps, like a snowball of loose flakes. Staudinger's claim was that there is no clump — the giant size is one real molecule, held by the same covalent bonds as any other.
How it came about
Staudinger was already a respected organic chemist, working at the ETH in Zürich, when he turned to the messy "colloidal" substances most chemists avoided. In a 1920 paper bluntly titled "On Polymerization", he laid out the case that polymerization is a normal chemical reaction stringing small units into long chains — then spent the next decade proving it against fierce resistance.
His strongest experiment was almost theatrical. If rubber were really a heap of small molecules held together by their double bonds, then chemically removing those double bonds — by adding hydrogen — should make it crumble into small pieces. Staudinger hydrogenated rubber, and it stayed rubbery and still behaved as a giant molecule. Solution viscosity gave him a second weapon: the longer the chain, the thicker the solution, in a regular way he turned into a ruler for molecular weight. At a now-famous 1926 meeting in Düsseldorf he faced a room of hostile colleagues; within a decade the evidence had won, and in 1953 he received the Nobel Prize.
Why it mattered
Almost everything made of plastic, rubber or synthetic fibre exists because we learned to treat these materials as chains we can design: make the chains longer, branch them, or cross-link them, and you tune strength, stretch and melting point. And the same idea reorganised biology — proteins, starch, cellulose and DNA are all macromolecules, long chains whose order and length carry their function.
A way to picture it
Think of a strung bead necklace versus a heap of loose beads. The old theory said rubber was a pile of separate beads sitting close together; pick it up and it would scatter. Staudinger said the beads are strung — one continuous thread runs through all of them, so it is a single object you can lift as one. Cut the forces between loose beads and the pile collapses; a strung necklace does not. Staudinger's hydrogen experiment did exactly that cutting — and the material held together, because it was a necklace all along.
Where it sits
Nineteenth-century chemistry had mastered the small molecule — Kekulé's benzene ring and van 't Hoff's tetrahedral carbon, both elsewhere in this Library — but balked at the large. Staudinger extended structural chemistry to the giant molecule, and in doing so prepared the ground for understanding life's own polymers: the proteins, and the DNA double helix worked out a generation later.