Conventional free radical polymerization is among the most frequently employed polymerization procedures to prepare over 100 million tons of commercial polymers. However, these polymers are ill-defined with high dispersity, uncontrolled molecular weight, topology, or composition. This is due to a very short lifetime of propagating radicals (<1 second) and slow initiation. New controlled radical polymerization (CRP) procedures (also called reversible deactivation radical polymerization) dramatically changed the control of polymer microstructure, enabling concurrent growth of polymer chains within minutes, hours, or even days. resulting in well-defined polymeric materials. Copper-based ATRP (atom transfer radical polymerization) catalytic systems with polydentate nitrogen ligands are among the most efficient CRP systems. Recently, by applying new initiating/catalytic systems, Cu level in ATRP was reduced to a few ppm. ATRP of acrylates, methacrylates, styrenes, acrylamides, acrylonitrile and other vinyl monomers was controlled by various external stimuli, including electrical current, light, mechanical forces, and ultrasound, also in the presence of air.
