91�ȱ�

Alkenes can be used to make polymers.

Polymers are very large molecules made when many smaller, reactive molecules join together, end to end. The smaller molecules are called monomers.

In general:

lots of monomer molecules → a polymer molecule

The polymers formed are called addition polymers.

This slideshow shows how several chloroethene monomers can join end to end to make poly(chloroethene), also called PVC:

The method can be summarised as follows:

• monomers have their double bonds broken
• large numbers of monomer molecules will join together
• it forms a long chain called a polymer

Alkenes can act as monomers because they are unsaturated:

• ethene can polymerise to form poly(ethene), also called polythene
• propene can polymerise to form poly(propene), also called polypropylene
• chloroethene can polymerise to form poly(chloroethene), also called PVC
• tetrafluoroethene can polymerise to form poly(tetrafluoroethene), also called PTFE or Teflon