Question

Explain the following terms giving a suitable example for each.

(i) Elastomers

(ii) Condensation polymer

(iii) Addition polymers

Answer 1

(i) Elastomers:

They have the weakest attraction force in between polymeric chains. Hence, they are amorphous with a high degree of elasticity. They have the ability to stretch out over ten times the original length and get back to their original position after removing the force.

For example, Buna-S, Buna-N, Neoprene

(ii) Condensation Polymerization:

When both reactants of a chemical reaction are bi-functional, they undergo a series of condensation reactions and form a polymer chain. This type of polymerization is called condensation polymerization. The condensation polymerization takes place in a stepwise manner with the loss of simple molecules like water, carbon dioxide, alcohol, $HCl$, etc.

Condensation polymerization starts from the condensation reaction of two reactant molecules and forms a dimer.

For example, condensation polymerization of terephthaloyl chloride and ethylene glycol forms a polyester known as poly (ethylene terephthalate) by the elimination of hydrochloric acid.

(iii) Addition Polymerization:

Monomer units, added to grow a polymer chain caring a reactive intermediate like free radical, carbocation or carbanion, is known as addition polymerization. Since it forms a long polymer chain, it is also known as chain-growth polymerization.

For example, ethene $(H_{2}C=C{H}_2)$ is polymerized for polythene.