Q.What are addition and condensation polymerisation. Give one example of each.

Addition polymers form by adding unsaturated monomers (no by-product); condensation polymers form by combining monomers with loss of a small molecule.

Addition (chain-growth) polymerisation:

• The monomers are unsaturated (contain C=C double bonds).
• They add repeatedly to one another to form the polymer without the elimination of any small molecule, so the polymer has the same empirical formula as the monomer.
• Example: ethene forms polythene: n CH2=CH2 -> -(CH2-CH2)n-. (Other examples: PVC from vinyl chloride, polystyrene from styrene.)

Condensation (step-growth) polymerisation:

• The monomers are usually bifunctional (have two reactive functional groups).
• They combine through repeated condensation, and in each step a small molecule such as water, HCl or ammonia is eliminated. …