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Nylon is in toothbrushes, ropes, clothes and parachutes. It was not found by accident. It came out of a research programme designed to answer a scientific question: can we build giant molecules on purpose, one bond at a time? This post tells the story of Wallace Carothers, works through the chemistry of nylon-6,6, and lists the mistakes students make with condensation polymers.
Who was Wallace Carothers?
The Science History Institute biography gives the outline. Carothers (1896–1937) studied accountancy before completing a chemistry degree at Tarkio College in Missouri, then earned a doctorate at the University of Illinois in 1924. He was a young instructor at Harvard, already interested in polymers, when Charles Stine of DuPont recruited him for a new programme of fundamental research.
At the time, as our post on Hermann Staudinger explains, many chemists still doubted that true giant molecules existed. Carothers set out to make them by reactions whose every step was known.
What was his plan?
His idea was to use condensation reactions, the same kind that make an ester from an acid and an alcohol, but with molecules that have a reactive group at each end. Each reaction links two molecules and releases a small molecule such as water. Because both ends stay reactive, the chain keeps growing. In 1929 he published an introduction to the general theory of condensation polymers in the *Journal of the American Chemical Society*.
How did neoprene and the first fibres come about?
The Science History Institute records that in April 1930 his assistant Arnold Collins isolated chloroprene, a liquid that polymerised by itself into a rubbery solid. As neoprene, it became the first commercially successful synthetic rubber. The group published it in 1931 as "a new synthetic rubber: chloroprene and its polymers".
Soon after, another colleague, Julian Hill, made a strong, elastic fibre from a polyester while trying to reach very high molecular weights. Carothers and Hill published artificial fibres from synthetic linear condensation superpolymers in 1932. But those polyesters melted too easily and dissolved in dry-cleaning solvents, so Carothers set fibres aside.
How did the switch to amines produce nylon?
His manager, Elmer Bolton, pushed him to return to fibres. The Science History Institute says that in early 1934 the team used amines instead of glycols, making polyamides instead of polyesters. Polyamides proved more stable, and the group soon found an outstanding polyamide fibre, later named nylon.
The US patent 2,130,948 for a "Synthetic fiber", with Carothers as inventor and DuPont as assignee, was filed on 9 April 1937 and granted on 20 September 1938. Nylon went into production in 1939, and stockings made from it were displayed at the New York World's Fair that year.
Worked example: the chemistry of nylon-6,6
Nylon-6,6 forms from hexamethylenediamine, H₂N(CH₂)₆NH₂ (C₆H₁₆N₂), and adipic acid, HOOC(CH₂)₄COOH (C₆H₁₀O₄). The "6,6" counts the carbon atoms in each monomer. Each repeat unit contains one of each monomer joined by two amide bonds, and two water molecules leave.
Use C = 12.011, H = 1.008, N = 14.007, O = 15.999 g/mol.
Diamine: 6(12.011) + 16(1.008) + 2(14.007) = 72.066 + 16.128 + 28.014 = 116.208 g/mol.
Adipic acid: 6(12.011) + 10(1.008) + 4(15.999) = 72.066 + 10.080 + 63.996 = 146.142 g/mol.
Water: 2(1.008) + 15.999 = 18.015 g/mol.
Repeat unit: 116.208 + 146.142 − 2(18.015) = 226.320 g/mol, matching C₁₂H₂₂N₂O₂.
How many repeat units in a chain of molar mass 20,000 g/mol? n = 20,000 ÷ 226.32 ≈ 88.
How much water is released when 1 kg of nylon-6,6 forms? Moles of repeat units = 1000 ÷ 226.32 ≈ 4.419 mol. Each releases 2 mol of water, so 8.837 mol × 18.015 g/mol ≈ 159 g.
Common mistakes:
Taking the repeat unit as diamine + acid without subtracting the water.
Subtracting one water instead of two. Each repeat unit has two amide links.
Mixing up nylon-6,6 (two monomers) with nylon-6, made from a single monomer, caprolactam.
Calling nylon an addition polymer. Anything that releases a small molecule as it links is a condensation polymer.
How did the story end for Carothers?
The Science History Institute records that Carothers suffered worsening depression and died by suicide in April 1937, before nylon reached the market. His story is a reminder that brilliant work and serious distress can exist together. If you or a friend is struggling, talk to someone you trust. In India, Tele MANAS, the national mental health helpline, is free on 14416 or 1-800-891-4416.
What can a student take from Carothers?
Ask one clear question and build toward it. His group did not search at random. They asked whether giant molecules could be built bond by bond, and chose reactions that made the answer visible.
Keep failed results. The polyester fibres failed as products but showed the method worked, and they pointed toward polyamides.
Do the bookkeeping. In condensation chemistry, every link costs a small molecule. Count it every time.
For more practice on how polymers are classified and calculated, read our guide to addition and condensation polymers. If a calculation like the one above goes wrong and you cannot see where, the Fermi Problem Library has a step-by-step solver that explains the reasoning rather than printing an answer.
Your next step: repeat the worked example for nylon-6,10, made from hexamethylenediamine and sebacic acid (C₁₀H₁₈O₄), and find its repeat-unit molar mass.
