livingpolymerisering

Living polymerization is a mode of chain-growth polymerization in which the active chain ends do not undergo irreversible termination or undesirable chain transfer during propagation. In an ideal living system, the rate of chain growth is determined by the monomer-to-initiator ratio, and the polymer chains keep growing when additional monomer is introduced. This behavior yields polymers with predictable molecular weights and narrow molecular weight distributions, and it enables precise control over polymer architecture, end-group functionality, and sequence.

Historically, living polymerization began with anionic polymerization of vinyl monomers in dry, aprotic solvents using highly reactive initiators such as organolithium species. This approach requires strict exclusion of moisture and oxygen and is most suitable for selected monomers like styrene, butadiene, and isoprene. In radical chemistry, living characteristics are achieved through controlled radical polymerization methods, notably RAFT (reversible addition–fragmentation chain-transfer), ATRP (atom transfer radical polymerization), and nitroxide-mediated polymerization (NMP). These techniques suppress most termination and transfer reactions, providing predictable growth while expanding monomer scope and reaction conditions.

The ability to form block and complex architectures is a hallmark of living polymerization. By sequentially adding different monomers, block copolymers and multiblock sequences can be prepared with defined block lengths. End-group fidelity allows subsequent chemical transformations, and polydispersity indices approach near-ideal values. Limitations include sensitivity to impurities, oxygen, and water, which can terminate chains; monomer and solvent choice, temperature, and catalyst systems also influence control. Despite challenges, living polymerization remains a foundational concept enabling precise macromolecular design across materials science, with applications ranging from advanced plastics to biocompatible polymers.