Definitions

Addition polymerisation, also called polyaddition or chain growth polymerization, is a polymerisation technique where unsaturated monomer molecules add on to a growing polymer chain one at a time . It can be represented with the chemical equation:
$nM \left(monomer\right) rightarrow \left(-M-\right)_n \left(polymer\right)$

where n is the degree of polymerization.

## Characteristics

The main characteristics are:

• polymerisation process takes place in three distinct steps:
• chain initiation, usually by means of an initiator which starts the chemical process. Typical initiators include any organic compound with a labile group: e.g. azo (-N=N-), disulfide (-S-S-), or peroxide (-O-O-). Two examples are benzoyl peroxide and AIBN.
• chain propagation
• chain termination, which occurs either by combination or disproportionation. Termination, in radical polymerisation, is when the free radicals combine and is the end of the polymerisation process.
• some side reactions may occur, such as: chain transfer to monomer, chain transfer to solvent, and chain transfer to polymer.
• unlike condensation polymerisation (also known as step-growth polymerization):
• high molecular weight polymer is formed at low conversion
• no small molecules, such as H2O, are eliminated in this process
• new monomer adds on the growing polymer chain via the reactive active centre which can be a
• the monomer molecule can be a
• given special reactants and reaction conditions an addition polymerization can be considered a living polymerization.
• above a certain ceiling temperature, no polymerisation occurs.

## References

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