What Are Polymers?

Think of polymers like incredibly long chains where each link is a simple molecule joined by covalent bonds. The name literally means "many parts" from the Greek words 'poly' (many) and 'meros' (parts). These massive molecules act as electrical insulators at room temperature, which is why they're perfect for coating wires and making phone cases.

Natural polymers come from living things and have been around for millions of years. Your DNA is actually a polymer that stores all your genetic information! Other examples include starch (found in potatoes and bread), silk (produced by silkworms for their cocoons), rubber (from rubber trees), and proteins (like the keratin in your hair).

Synthetic polymers are man-made materials created in laboratories using chemicals extracted from the earth's crust. You encounter these daily: polyester in your school uniform, nylon in sports gear, poly(ethene) in shopping bags, polystyrene in takeaway containers, and Kevlar in bulletproof vests.

Quick Tip: Remember that all polymers are large molecules, but not all large molecules are polymers - they specifically need to be made of repeating units!

How Polymers Form Through Polymerisation

Polymerisation is the chemical process where small molecules called monomers join together under specific conditions. Scientists subject monomers to high pressures and pass them over a catalyst to trigger the binding process - it's like forcing puzzle pieces to connect!

Let's look at ethene, a simple monomer with the formula C₂H₄. Each ethene molecule contains a reactive double covalent bond between two carbon atoms. This double bond is the key to polymerisation because it makes the molecule unstable and eager to react.

During polymerisation, the double bond splits, creating two "sticky" ends on the ethene molecule. These reactive ends immediately grab onto other ethene monomers, forming a growing chain. As more and more ethene molecules join together, they create poly(ethene) - the plastic used in carrier bags and food packaging.

The beauty of this process is that it can continue almost indefinitely, creating chains with hundreds or thousands of monomer units. This is why polymers have such different properties from their starting materials - a gas like ethene becomes a solid plastic through polymerisation!

Exam Focus: You'll need to recognise the ethene structure $H₂C=CH₂$ and explain how the double bond breaks to allow polymerisation.