Propagation in the cationic ring-opening polymerization of oxygen-containing heterocyclic monomers involves nucleophilic attack of oxygen atoms from the monomers on the cationic growing species. If hydroxyl groups containing compounds were present in the system

propagation may proceed with another mechanism which is known as activated monomer (AM) mechanism. For a long time

scholars' research focus mainly concentrated in the active chain end (ACE) mechanism

with the deepening of theoretical research and the development of testing technology

AM cationic polymerization of heterocyclic monomers was put forward. This review summarized the molecular mechanism of the existence of AM mechanism in the cationic ring-opening polymerization of oxygen-containing heterocyclic monomers. The paper also reviewed the chemical condition for initiating AM mechanism occurrence. Then

the AM mechanism was used as a tool to product block

star-like and hyperbranched polymers recently is summed.