Which polymerization involves the formation of a small molecule, such as water, in addition to the polymer?

• A. Addition polymerization
• B. Condensation polymerization
• C. Fractional distillation
• D. Hydrolysis

Answer: (B)

Condensation polymerization is the process where polymer chains grow by linking monomer units and releasing a small molecule, such as water, in the process. Each time two functional groups react, a byproduct is formed and the polymer chain extends. This is how polyesters and polyamides are made: diol with diacid or diamine with diacid release water as the monomers join. In contrast, addition polymerization builds polymers by simply adding monomers without losing a byproduct, so no small molecule is formed each time a linkage is made. Hydrolysis is the opposite of polymerization, breaking bonds with water, and fractional distillation is a separation technique, not a polymerization method. So the description that involves forming the polymer with loss of a small molecule like water points to condensation polymerization.