Atom transfer radical polymerization (ATRP) is a successful example of controlled radical polymerization which involves equilibria between growing chain radicals and their dormant counterparts. It is different from conventional free radical polymerization because of the ability of a redox-active transition metal complex to affect the reversible activation/deactivation rate of the growth center. As the name implies, the atom transfer step is crucial in the whole polymerization procedure, which is
