Which of the following best describes a condensation polymerisation process?

• A. It produces a small molecule as a by-product
• B. It requires a double bond to break
• C. It never forms polymers
• D. It uses only inert substances

Answer: (A)

Condensation polymerisation is when monomers join and a small molecule is expelled each time, such as water or methanol. That release of a by-product is what defines this type of polymerisation, so saying a small molecule by-product is produced is the best description. For example, nylon and PET polymers form with water released during the linking of monomer units. The reaction doesn’t require breaking a double bond in the monomers; many condensation reactions involve reacting functional groups like –COOH and –OH or –NH2 to form new bonds without needing an existing C=C bond to open. It certainly forms polymers, so the idea that it never forms polymers isn’t correct. And it doesn’t use only inert substances; the reactants must be chemically reactive functional groups to form the bonds and release the small molecule.