Photocontrolled Living Polymerization Systems with Reversible Deactivations through Electron and Energy Transfer.

Recently, visible-light-regulated polymerization has been gaining popularity, as it opens a range of new opportunities for the synthesis of functional polymers and materials. Here, the most recent developments in this field are summarized, which is the use of photocatalysts and catalyst-free approaches to mediate polymerization upon photoexcitation. These catalysts can transfer an electron or energy to activate an initiator. The recent achievements in light-regulated atom-transfer radical polymerization, reversible addition-fragmentation chain-transfer polymerization, ring-opening metathesis polymerization, cobalt-mediated radical polymerization, iodine-mediated radical polymerization, and living cationic polymerization are reviewed. Recent development in these fields have solved important challenges in polymer chemistry, such as the development of oxygen-tolerant polymerization, polymerization mediated by near-infrared, metal-free polymerization, and spatial-, temporal-, and sequence-controlled polymerization. Some applications of these techniques will be discussed, such as adapting the current photocatalytic systems to synthesize heterogeneous photocatalysts that act as recyclable photocatalysts and novel light-mediated approaches for surface functionalization of hybrid materials and living cells. Finally, the existing challenges in polymer chemistry that could be overcome by further development of light-mediated polymerization techniques are highlighted along with the future directions of this field.