The development of an atom transfer radical polymerization (ATRP) system without any transition metal catalyst for electronic and biomedical applications was considered to be in pressing need. Fluorescein (FL) was used as the organic photocatalyst for the polymerization of methyl methacrylate (MMA) via the proposed photoinduced electron transfer–atom transfer radical polymerization (PET–ATRP) mechanism. In the presence of electron donors provided by triethylamine (TEA), fluorescein can activate alkyl bromide and control radical polymerizations by a reductive quenching pathway. The polymerizations could be controlled by an efficient activation and deactivation equilibrium while maintaining the attractive features of “living” radical polymerization. The number-average molecular weight M_n,GPC increased with monomer conversion, and the controllability of molecular weight distributions for the obtained PMMA could be achieved in the polymerization processes. MALDI-TOF MS, ¹H NMR spectroscopy and chain extension polymerizations show reserved chain-end functionality in the synthesized polymers and further confirm the “living” feature of the metal-free ATRP methodology. All these research results support the feasibility of the visible light mediated metal-free PET–ATRP platform for the synthesis of elegant macromolecular structures.

Activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) was introduced by Matyjaszewski and coworkers in 2005. The development of AGET ATRP has profound industrial implications because it lowers the amount of necessary catalyst, while still allowing excellent control over molecular weight and molecular weight distribution. Herein, we highlight recent works on the mechanistic understanding of AGET ATRP towards the advance of catalysis and the design and synthesis of functional polymers, with a particular emphasis on: (a) mechanistic understanding of AGET ATRP; (b) reduction of catalyst concentration; (c) aqueous-phase systems by AGET ATRP; (d) iron-mediated AGET ATRP; and (e) functionnal polymers designed by AGET ATRP. AGET ATRP is a robust tool due to its simplicity, broad applicability, and its ability to prepare previously inaccessible well-defined polymeric materials.

It is well known that the recently developed photoinduced metal‐free atom transfer radical polymerization (ATRP) has been considered as a promising methodology to completely eliminate transition metal residue in polymers. However, a serious problem needs to be improved, namely, large amount of organic photocatalysts should be used to keep the controllability over molecular weights and molecular weight distributions. In this work, a novel photocatalyst 1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene (4CzIPN) with strong excited state reduction potential is successfully used to mediate a metal‐free ATRP of methyl methacrylate just with parts per million (ppm) level usage under irradiation of blue light emitting diode at room temperature, using ethyl α‐bromophenyl‐acetate as a typical initiator with high initiator efficiency. The polymerization kinetic study, multiple controlled “on–off” light switching cycle regulation, and chain extension experiment confirm the “living”/controlled features of this promising photoinduced metal‐free ATRP system with good molecular weight control in the presence of ppm level photocatalyst 4CzIPN. image