Question

How are polymers classified on the basis of polymerisation process?

Answer 1

On the basis of mode of polymerisation, polymers are classified into the following groups:

Addition polymers or chain growth polymers:

1. A polymer formed by direct addition of repeated monomers without the elimination of byproduct molecules is called addition polymer.
2. In this, the monomers are alkenes, alkadienes (or their derivatives) or alkynes.
3. All the atoms of monomers are present in the addition polymer and they have the same empirical formula as their monomer. eg. Orlon/ acrilan / polyacrylonitrile (PAN):

Condensation polymers or step growth polymers:

1. A polymer formed by the condensation of two or more than two monomers with the elimination of simple molecules like water, methyl alcohol, hydrogen
   chloride, ammonia, etc. is called condensation polymer.
2. In this, bifunctional or trifunctional monomeric units undergo condensation.
3. All the atoms of monomers are not present in the condensation polymer.
4. There are ester or amide linkages in the condensation polymer.
5. Condensation polymer is formed in a stepwise manner (dimer, tetramer, … and so on).
   eg. Nylon-6,6: