Types of Polymerisation Reactions

The two big families of polymerisation

Every polymer is built by one of two broad mechanisms:

• Addition (chain growth) polymerisation
• Condensation (step growth) polymerisation

Addition polymerisation

Here, monomer molecules — either all of the same kind or a mix of different kinds — simply add on to each other, one after another, to build up a long chain. Nothing is lost in the process; the polymer contains all the atoms of the monomers that went into it.

• The monomers must be unsaturated compounds — alkenes, alkadienes, and their derivatives — because it is the breaking of a C=C (or similar) double bond that lets each new monomer attach to the growing chain.
• As monomer after monomer adds on, the chain keeps getting longer — this is why the process is also called chain growth polymerisation. …