Condensation polymerisation

Think of condensation polymerisation as basically two molecules joining together, and each time they join, they kick out a tiny molecule.

For example, imagine these two molecules:

{HO—R—OH}}

This is a diol. It has an –OH at both ends.

And:

{HOOC—R—COOH}}

This is a dicarboxylic acid. It has a –COOH at both ends.

What happens?

An –OH from the carboxylic acid and an H from the alcohol are removed:

OH + H → H2O

The remaining molecules then join together:

{—C(=O)—O—}}

That new connection is an ester link.

⬇ join together

{Monomer—Monomer} + H_2O

Then this happens again and again:

\boxed{A-B-A-B-A-B-A-B-A-B}

until you have a huge molecule — a polymer.

⭐ The key idea

Condensation polymerisation =

\boxed{\text{monomers join} + \text{small molecule comes out}}

Usually, for NCEA, that small molecule is H₂O.

If you want, I can show you an actual NCEA-style example with displayed structural formulas, which makes it much easier to see.