Organic Chemistry: Polymers

Organic Chemistry: Polymers

Basic Properties

  • Polymers are large molecules made by joining together many smaller molecules, known as monomers.
  • The process by which monomers combine to form a polymer is called polymerisation.
  • Most polymers contain carbon and hydrogen, just like other organic compounds, but may also contain other elements such as oxygen, nitrogen, and chlorine.
  • The structures of polymers can be linear, branched, or cross-linked depending on their formation and the types of monomers used.

Examples of Polymers

  • Polyethylene, the most common plastic, is a polymer of ethene.
  • Polypropylene, another common plastic, is a polymer of propene.
  • Polystyrene is a polymer of styrene (phenylethene).
  • PVC (polyvinyl chloride) is a polymer of vinyl chloride.

Nomenclature of Polymers

  • The names of polymers typically begin with ‘poly-‘ followed by the name of the monomer used, often in its common rather than IUPAC name.
  • For instance, the polymer made from ethene monomers is named polyethene, although the correct IUPAC name for the monomer is ethylene.

Structure of Polymers

  • In addition polymerisation, the double bonds in the monomer molecules open up, allowing them to join together to form long chains.
  • Sometimes, polymer chains can have branches, forming a branched structure.
  • Different forms of a polymer can have different properties. For instance, low-density polyethene (LDPE) has a branched structure, which makes it more flexible than high-density polyethene (HDPE), which has a linear structure.
  • Condensation polymerisation occurs when two different types of monomers combine, losing a small molecule as a byproduct, often water.

Reactions of Polymers

  • Polymers have strong C-C and C-H bonds, making them resistant to reaction.
  • However, most polymers are not completely inert. They can be broken down under suitable conditions, such as high temperature.
  • Although resistant to many chemical reactions, most polymers undergo slow oxidation when exposed to the atmosphere and light.

Uses of Polymers

  • Polymers have a wide range of applications: from everyday products such as plastic bags, bottles, and toys to advanced uses in the medical field like heart valves and artificial limbs.
  • Some polymers, including polypropene and polystyrene, are used for insulation and packaging.
  • Poly(ethene terephthalate) or PET is used for beverage containers and synthetic fibres.
  • Polyvinyl chloride (PVC) is used in piping, window frames, and vinyl siding.