Explanation

It is also called chain polymerization. polymerization with rapid chain growth initiated by reactive species. chain polymerization is characterized by that the polymerization process consists of three elementary reactions, namely chain initiation, chain growth and chain termination, sometimes accompanied by chain transfer reaction. The rate and activation or conditioning energy of each elementary reaction are quite different. chain initiation is the formation of active center, chain growth is the reaction between monomer and active center, and chain termination is the disappearance of active center. monomer can only react with active center to generate new active center, and monomer cannot react with each other. The polymerization system is always composed of monomer, polymer and trace initiator, and there is no intermediate product with increasing molecular weight. According to reactive species, chain polymerization can be divided into free radical polymerization, ionic polymerization and coordination polymerization, and ionic polymerization can be divided into cationic polymerization and anion polymerization. According to different initiation methods, chain polymerization can also be divided into initiator (or catalyst) initiated polymerization, thermal initiated polymerization, photo-initiated polymerization, radiation polymerization, biochemical polymerization, electrochemical initiated polymerization and mechanochemical polymerization. The addition polymerization of vinyl monomer mostly belongs to chain polymerization. According to the production estimate, about 70% of modern synthetic macromolecule materials are synthesized by chain polymerization, such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polylctrafluorocthylone, polymethyl methacrylate, polyacrylonitrile, acrylonitrile-butadi- ene-styrene copolymer, block copolymer of styrene and butadiene, styrene butadiene rubber, acrylonitrilebutadiene rubber and chloroprene rubber are all products of chain polymerization.

Classification