Polymers

Polymers are very large molecules which are made by linking many smaller, identical molecules known as monomers. These monomers are joined together by strong covalent bonds.

  • There is no fixed number of atoms in the chain of any given polymer.

One well-known example of a polymer is poly(ethene).

Four ethene molecules are displayed in their structural formula with an arrow pointing down to the polymer of ethene (polyethene),

In this example of polyethene, four ethene molecules join to form a poly(ethene) chain. However, in reality, poly(ethene) molecules can contain thousands of these monomers in a chain.

Due to the numerous atoms and covalent bonds in a polymer molecule, it’s often easier to represent them using repeating units. For example, the diagram below shows the repeating unit of poly(ethene).

Repeating unit of polyethene.
  • The line through brackets tells us that the polymer molecule extends out in both directions.
  • The value of “n” tells us the number of repeating units that are joined together. This value can vary and is often a very large number.

Properties of Polymers

One key property of polymers is the presence of strong intermolecular forces. These forces exist between polymer molecules, which are notably strong due to the large size of the molecules. Because of these strong forces, it takes a lot of energy to break the bonds between the polymer molecules. As a result, polymers often have high melting and boiling points and are typically solids at room temperature.

In comparison, smaller molecules have weaker intermolecular forces, which makes them easier to break apart. This results in lower melting and boiling points, and smaller molecules are often liquids or gases at room temperature.

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