Polymers: Long Chains of Repeating Units

0:00What do wood, DNA and a plastic bag have in common?

0:05They are all made of polymers, built from small molecules called monomers. Picture one monomer as a paper clip.

0:14Monomers join end to end, like paper clips linked into a chain.

0:19Poly means many, so a long chain of many monomers is called a polymer.

0:26In many polymers, the very same unit repeats again and again, often thousands of times in one chain.

0:34Living things make natural polymers: cellulose in wood and cotton, starch in potatoes, proteins in hair, DNA in your cells, and rubber from tree sap.

0:46Indigenous peoples have used them for thousands of years, making rope from plant fibres and balls from rubber.

0:54So not all polymers are plastics made by people.

0:58Synthetic polymers are made by people: polyethylene in plastic bags, nylon in clothing, and PVC in pipes.

1:07In a material, chains lie side by side, held together by weak forces.

1:14Longer chains have more of these forces, so the material is usually stronger.

1:20Some polymers also have cross-links, strong bonds between chains that stop them sliding, so the material holds its shape.

1:30Most plastics break down very slowly, so they last a very long time.

1:36That makes them useful, but it also makes plastic waste a pollution problem.

1:42Polymers are long chains of repeating units called monomers, made by nature and by people.