A polymer is a large molecule made up of lots of small molecules. In the natural world, fats and proteins are polymers. A monomer is the name for the small molecule that is part of the chain, in the following example, the monomer is ethene.
The monomers are passed over a heated catalyst and polymerisation occurs. In this example a long chain of molecules called poly(ethene) or polythene is made.
NB: the molecule in square brackets shows the structure of each monomer and the lines coming out show how they are bonded to each other. The letter n denotes that the sequence is repeated many times.
Addition polymerisation is the creation of polymers from monomers containing a C=C bond. As the name suggests it is an addition reaction, and is written as follows:
Above shows the formation of polystyrene, however, many groups could be attached to the C=C, with 4 Fluorenes, Teflon would be made. And a single methyl group results in polypropene.
Polyalkenes are made by the addition polymerization of alkenes. They contain many carbon bonds, which means there is little bond polarity and they are therefore inert which means they are not biodegradable.
Condensation polymers are formed by the reaction of molecules with two functional groups and produces water as a by-product. The first example is the formation of polyesters by the reactions of dicarboxylic acids and diols, forming ester links. For example, in the production of Terylene.
A polyamide is another polyester formed by condensation. It is formed by the reaction of dicarboxylic acids and diamines. This is how Nylon-6,6 is made:
Unlike addition polymers, polyamides and polyesters are biodegradable and can be broken in to their constituent molecules by hydrolysis where water is added to the polymer.
Uses and others
Polymers are very useful, and are used ti replace traditional materials like metals, paper and rubber. The following table shows some other polymers along with their uses.