Anionic polymerization is a type of chain-growth polymerization that involves the use of anions, or negatively charged ions, to initiate the reaction. This process typically requires a monomer with a double bond, such as styrene or butadiene, which reacts with the anion to form a reactive site. The reaction proceeds by adding more monomer units to this site, resulting in a long polymer chain. This method is known for producing polymers with a high degree of control over molecular weight and structure. Anionic polymerization is often used to create specific types of polymers, such as polystyrene or polybutadiene, which have various applications in industries like plastics and rubber.