Controlled/living radical polymerization techniques have transformed polymer chemistry in the last few decades, affording the production of polymers with precise control over both molecular weights and architectures. It is now possible to synthesize almost an infinite variety of macromolecules using nonspecialized equipment, finding applications in high-tech industry. However, they have several shortcomings. Until recently, living radical polymerizations could not be controlled by an external stimulus, such as visible light, pH, mechanical, chemical, etc. Moreover, they are usually sensitive to trace amounts of oxygen in the system. In this Article, we report a photoinduced living polymerization technique, which is able to polymerize a large range of monomers, including conjugated and unconjugated monomers, using ultralow concentrations of an iridium-based photoredox catalyst (typically 1 ppm to monomers) and a low energy visible LED as the light source (1-4.8 W, λ(max) = 435 nm). The synthesis of homopolymers with molecular weights ranging from 1000 to 2,000,000 g/mol was successfully achieved with narrow molecular weight distributions (M(w)/M(n) < 1.3). In addition, chain extensions of poly(methacrylate)s, poly(styrene), poly(N-vinyl pyrrolidinone), poly(vinyl ester)s, and poly(acrylate)s were performed to prepare diblock copolymers. The reusability of the catalyst was demonstrated by the synthesis of a decablock polymer by multiple chain extensions. Most importantly, this process was employed to prepare well-defined polymers and multiblock copolymers in the presence of air.

His Ph.D. was in collaboration with Solvay-Solexis and devoted to the synthesis of new graft copolymers using grafting "to". In 2005, he undertook a postdoctorate position with Dupont Performance and Elastomers (Willmington, United States) and Dr. B. Ameduri dealing with the synthesis of original fluorinated elastomers using controlled radical polymerization (e.g., iodine transfer polymerization). Since October 2006, he has been a senior research fellow under the direction of Prof. Thomas Davis in the Centre of Advanced Macromolecular Design (CAMD), University of New South Wales. His research interests mainly cover the preparation of well-defined polymers, protein-polymer conjugates, and hybrid organic-inorganic nanoparticles using controlled radical polymerization. He has coauthored over 40 peer-reviewed research papers, including 2 book chapters, and 2 patents. Volga Bulmus received her B.E. and M.Sc. in Chemical Engineering and her Ph.D. in bioengineering (Hacettepe University, Turkey), in 2000. She worked as a postdoctoral research fellow in the Bioengineering Department at the University of Washington between 2001 and 2003. In 2004, she was granted a highly competitive The University of New South Wales (UNSW) Vice Chancellor's Research Fellowship (Australia). In 2008, she was appointed as a Senior Lecturer at the School of Biotechnology and Biomolecular Sciences (UNSW). She is also an adjunct member of The Centre for Advanced Macromolecular Design (CAMD) at UNSW. Dr. Bulmus leads a group of 5-10 researchers working on the development of advanced polymers for biotechnology and biomedical applications. She has published over 45 peer reviewed research papers. Her research interests include design, synthesis, and evaluation of well-defined polymeric systems for nanobiotechnology and drug delivery applications ranging from antitumor chemotherapy and gene silencing to bioseparations and biosensors. Tom Davis has been an academic at UNSW for 17 years following a stint in industry as a research manager at ICI in the U.K. He has coauthored 315+ reviewed papers, patents, and book chapters. He is the Director of the Centre for Advanced Macromolecular Design (CAMD) at UNSWsa Centre with expertise in bio/organic polymer synthesis and polymerization kinetics. He is also a visiting Professor at the Institute for Materials Research & Engineering (IMRE) in Singapore. In 2005 he was awarded a Federation Fellowship by the Australian Research Council. He serves (or has served) on the editorial advisory boards of Macromolecules,

Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

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The use of metalloporphyrins has been gaining popularity particularly in the area of medicine concerning sensitizers for the treatment of cancer and dermatological diseases through photodynamic therapy (PDT), and advanced materials for engineering molecular antenna for harvesting solar energy. In line with the myriad functions of metalloporphyrins, we investigated their capability for photoinduced living polymerization under visible light irradiation over a broad range of wavelengths. We discovered that zinc porphyrins (i.e., zinc tetraphenylporphine (ZnTPP)) were able to selectively activate photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization of trithiocarbonate compounds for the polymerization of styrene, (meth)acrylates and (meth)acrylamides under a broad range of wavelengths (from 435 to 655 nm). Interestingly, other thiocarbonylthio compounds (dithiobenzoate, dithiocarbamate and xanthate) were not effectively activated in the presence of ZnTPP. This selectivity was likely attributed to a specific interaction between ZnTPP and trithiocarbonates, suggesting novel recognition at the molecular level. This interaction between the photoredox catalyst and trithiocarbonate group confers specific properties to this polymerization, such as oxygen tolerance, enabling living radical polymerization in the presence of air and also ability to manipulate the polymerization rates (kp(app) from 1.2-2.6 × 10(-2) min(-1)) by varying the visible wavelengths.

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In this work, we demonstrate the use of organophotoredox catalysts under visible light to perform photoinduced electron transfer-reversible addition fragmentation chain transfer (PET-RAFT) for the polymerization of methacrylate monomers.

■ ACKNOWLEDGMENTS S.P.A. acknowledges the EPSRC for an Established Career Particle Technology Fellowship (EP/R003009), which provided postdoctoral support for N.J.W.P. C.B. thanks the Australian Research Council for his Future Fellowship (FT12010096).