What's the difference between addition and condensation polymers?

Understanding Polymerisation

Polymers are giant molecules built from smaller repeating units called monomers, but they don't all form the same way. The two primary methods—addition and condensation—differ fundamentally in how monomers combine and what they leave behind.

Addition polymerisation happens when unsaturated monomers, typically containing carbon-carbon double bonds, link together. This process requires just one type of monomer and results in one single product, as the double bonds open up to chain the molecules together without losing any atoms.

Condensation polymerisation is a bit more complex. It generally involves two different types of monomer that react with each other. Crucially, every time a new bond forms, a small molecule—frequently water—is eliminated. This means the reaction produces two distinct products: the main polymer chain and a small byproduct.