Cationic polymerisation

(Addition polymerisation)

The polymerisation of isobutylene (2- methyl propene) by traces of strong acid is an example of cationic polymerisation.
The chain growth ceases when the terminal carbocation reacts with a nucleophile or losses a proton to give terminal alkenes.
Monomers bearing cation stabilizing group such as alkyl shows this type of polymerisation.
This process generally occurs at low temperature in methylene chloride solution, where strong acid such as lewis acid containing traces of water acts as intiating reagents.
At low temperature there is no chain transfer reaction, thus linear ( not branched) polymers are formed.

Mechanism

Cationic polymerisation of isobutylene.

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Polymers

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