Addition and Condensation Polymerization
On the basis of method of polymerization the polymers are classified as addition polymers and condensation polymers.
Addition Polymer
A polymer formed by direct addition of repeated monomers without the elimination of any small molecule is called addition polymer. In this type, the monomers are unsaturated compounds and are generally derivatives of ethene. The addition polymers have the same empirical formula as their monomers. Examples are polyethene, polypropylene and polyvinyl chloride.
Condensation Polymer
A polymer formed by the condensation of two or more than two monomers with the elimination of simple molecules like water, ammonia, hydrogen chloride, alcohol, etc. is called condensation polymer. In this type, each monomer generally contains two functional groups. For example, nylon – 66 is obtained by the condensation of two monomers - hexa methylenediamine and adipic acid with the loss of water molecules. Examples of condensation polymers are Nylon 66, terylene, bakelite, and alkylresins.
Differences Between Addition Polymerization and Condensation Polymerization
| Addition Polymerization | Condensation Polymerization |
| Involves unsaturated monomers | Involves substances with at least 2 functional groups |
| Fast addition of monomers | Step-wise slow addition |
| At any instant, only monomer and polymers are present | No monomer. Mixtures of dimers, trimers and tetramers are present |
| Initiator is necessary to catalyze | Catalyst is not necessary |
| No small molecules are eliminated | Small molecules like are often eliminated |