There are three modes of polymerization depending upon the types of reactions taking place between the monomers.
1. Addition polymerization (or chain growth polymerization)
2. Condensation polymerization (or step growth polymerization)
3. Ring opening polymerization
4. Addition polymerization or chain growth polymerization : It is a process of polymers by the repeated addition of a large number of monomers is called addition polymerization (like alkenes) without loss of any small molecules.
Example : Formation of polyethylene from ethylene is well known example of addition polymerization. It is a chain growth polymerization.
5. Condensation polymerization or step growth polymerization : The process of formation of polymers from polyfunctional monomers with the elimination of some small molecules such as water, hydrochloric acid, methanol, ammonia is called condensation polymerization.
Example : The formation of terylene, a polyester polymer, from ethylene glycol and terephthalic acid. Condensation polymerization is a step growth polymerization.
6. Ring opening polymerization : The process of formation of polymers from cyclic compounds (like lactams, cyclic ethers, etc.) by ring opening is called ring opening polymerization.
Example : Polymerization of e-caprolactam.
Ring opening polymerization proceeds by addition of a single monomer unit to the growing chain molecules. It is a step growth polymerization.
