Addition versus condensation polymerisation Tamil revision mind map as a side by side comparison: addition polymerisation requiring a monomer with one carbon-carbon double bond that opens with no atoms lost so the repeating unit's molar mass equals the monomer's, giving polythene PVC polystyrene and PTFE, versus condensation polymerisation requiring monomers with reactive functional groups at both ends such as an amine and a carboxylic acid where a small molecule such as water is lost at every new bond, giving nylon as a polyamide and terylene as a polyester and Bakelite, with the repeating unit's molar mass therefore less than the sum of the monomers.