In the realm of organic chemistry, linking small molecules to create extended chains—polymers—is a foundational technique. This transformation, known as polymerization, merges many monomer units into a single, larger macromolecule.
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Condensation polymerization occurs when two or more monomers combine while releasing a small molecule, often water. A classic illustration involves glycine (HOOC–CH2–NH2). When two glycine molecules react, they form the dimer HOOC–CH2–NH–CO–CH2–NH2 and liberate a water molecule. The reaction requires at least one reactive site—such as a double bond or two single bonds—on each monomer.
Addition polymerization starts with a monomer that contains a reactive double or triple bond. Initiators—free radicals, cations, or anions—break the bond, enabling successive monomer units to add. Styrene (C6H5–CH=CH2) is a well‑known example; under free‑radical conditions it polymerizes into long polystyrene chains. Carbocationic polymerization, where acids generate positively charged carbocations, also produces extended chains such as polyacrylates.
