Anionic polymerization is a type of chain-growth polymerization that involves the use of anionic initiators to start the reaction. In this process, a negatively charged ion initiates the polymerization by attacking a monomer, which typically contains a double bond. This leads to the formation of a reactive site that can continue to add more monomer units, resulting in a long polymer chain. This method is particularly useful for creating polymers with specific structures and properties, such as polystyrene or polybutadiene. Anionic polymerization allows for better control over molecular weight and the distribution of polymer chains, making it valuable in producing high-performance materials.