Chain polymerization is a polymerization process in which the monomers combine to form a polymer through a chain of reactions. This reaction begins with the formation of a radical through initiation, often by heat or light. The monomer then combines with the radical, resulting in the release of a new radical, which then attaches another monomer.

The process continues until either all monomers are used up or chain termination occurs through inhibition. An important factor in chain polymerization is the choice of the initiator that initiates the formation of radicals. Commonly used initiators include azo compounds, organic peroxides and persulfates. Choosing the right initiator depends on the type of monomers, temperature and other conditions.

Chain polymerization is often used to produce plastics and polymers because it is a cost-effective and efficient method to produce large quantities of polymers. However, undesirable side reactions such as gel formation or branching can occur during polymerization. To avoid this, inhibitors such as phenols or copper ions can be added to suppress unwanted reactions.

Overall, chain polymerization is an important process for producing polymers and is of great importance in chemistry, materials science and engineering.