“Additional Polymerisation, monomers join together without the loss of atoms from the molecule.”

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“Additional Polymerisation, monomers join together without the loss of atoms from the molecule.”  (Reference 1)

Additional polymerisation is the process in which many monomers bond together to produce large chains called ‘Polymers’. Polyethene is an example of this. It is made of many ethene monomers linked together as one, commonly known as polythene.

In additional polymerisation, all the monomers are alkenes (contain a carbon-carbon double bond).  It is respectively this double bond that breaks and splits to form bonds with other ethene molecules.

                                                                        (Reference 3)

There are certain conditions that need to be met for the reaction to be carried out efficiently. These are:

This process starts with a new radical being donated, (a species with an unpaired electron.) In this case, it is donated from the oxygen, it is created by breaking the oxygen-oxygen bond, in such a way that the two electrons involved end up on the separated pieces of the original molecule, this is known as a ‘homolytic cleavage’.

E.g. Here is an example of a common inhibitor: Benzoyl Peroxide  

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        (Reference 4 )

The radical now combines with the spilt carbon-carbon double bond. The new radical continues to react with more alkenes and hence the chain grows.

Eventually two free radicals collide producing a final molecule, as this has a random timing the chain lengths can vary from 2000 molecules to 20000.  However, a chain can also combine with another growing chain if they were to rub together causing a bond to form between two carbons.

E.g.

(Reference 4 ) This shows

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