Types of polymerization
Types of polymerization:
Polymers can be synthesized by the following polymerization processes.
I. Addition polymerization (or) chain polymerization
II. Condensation or, step or, step growth polymerization
The addition polymerization is the process in which the liniking together of monomer molecules by a chain reaction is observed. Polymer synthesized by addition polymerization has the same empirical formula as that of monomer.
No molecule is evolved during polymerisation and the polymer is an exact multiple of the original monomeric molecule.
Ex: nCH2 = CH- (CH2 – CH2)n
Where P = pendant group
An intermolecular reaction involving two different bifunctional reactants with affinity for each other and taking place through repeated condensation reaction is known as condensation polymerization.
* Monomers having – COOH and – OH or, -COOH and –NH2 undergo condensation polymerization.
The reaction always accompanies the elimination of H2O, HCl, CH3OH, NH3 molecules.
1) Nylon 6.6 : [polymerization involving adipic acid and hexamethylene diamine]
2) Terelene: (polyethylene terephthalate) [polymerization involving ethylene glycol anol terephthalic acid]
3) Polyurethane: Polymerisation involving a diol
Ex: bisphenol A) and a diisocyanate (ex: toluene diisocyanate) to give polyurethane.
Condensation polymerization involving trifunctional reactants give rise to a cross – linked three-dimensional polymer.
Addition polymerisation involving a mixture of two (or) more suitable or compatible monomers gives a copolymer and the process is known as copolymerization.
A reaction in which a mixture of two (or) more monomers is allowed to undergo polymerisation is known as copolymerization. The polymer is known as copolymer.
1) Copolymerisation of styrene and methyl methacrylate
2) Copolymerisation of acrylo nitrile and vinyl chloride
3) Copolymerisation of styrene and 1, 3 – buta diene.
mCH2 = CH n CH2 = CH – CH = CH2 copolymerisation.