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.

The application of external stimuli such as light to induce controlled radical polymerization reactions has important implications in the field of materials science. In this study, the photoactivation of trithiocarbonates (TTCs) (i.e., conventional RAFT agents) by visible light (∼460 nm) is investigated, and the ability of TTCs to control radical polymerization under visible light in the complete absence of exogenous photoinitiators or catalysts is demonstrated for the first time. By selectively exciting the spin-forbidden n → π* electronic transition, polyacrylates and polyacrylamides of low dispersity and high end group fidelity were obtained. In addition, this approach allows for the efficient synthesis of well-defined linear, (multi)block, and network (co)polymers. This study demonstrates the versatility of our strategy to generate polymers with controllable properties by visible light, which may be highly useful for applications such as surface patterning.

Recent developments in polymerization reactions utilizing thiocarbonylthio compounds have highlighted the surprising versatility of these unique molecules. The increasing popularity of reversible addition–fragmentation chain transfer (RAFT) radical polymerization as a means of producing well‐defined, ‘controlled’ synthetic polymers is largely due to its simplicity of implementation and the availability of a wide range of compatible reagents. However, novel modes of thiocarbonylthio activation can expand the technique beyond the traditional system (i.e., employing a free radical initiator) pushing the applicability and use of thiocarbonylthio compounds even further than previously assumed. The primary advances seen in recent years are a revival in the direct photoactivation of thiocarbonylthio compounds, their activation via photoredox catalysis, and their use in cationic polymerizations. These synthetic approaches and their implications for the synthesis of controlled polymers represent a significant advance in polymer science, with potentially unforeseen benefits and possibilities for further developments still ahead. This Research News aims to highlight key works in this area while also clarifying the differences and similarities of each system.

The ultrasonic irradiation of aqueous solution is demonstrated to be a suitable source of initiating radicals for a controlled radical polymerization when conducted in the presence of a thiocarbonylthio-containing reversible addition-fragmentation chain transfer (RAFT) agent. This allows for a highly "green" method of externally regulated/controlled polymerization with a potentially broad scope for polymerizable monomers and/or polymer structures.

The photolytic stability of various RAFT agents (i.e., thiocarbonylthio-containing compounds) under irradiation from a blue LED light source has been investigated. The effect and implications of efficient photo-fragmentation and potential photo-degradation with regard to their performance in photopolymerization reactions is reported. The stability is found to depend strongly on the structure of the fragmenting (R-) group and the reactivity of the carbon-centered radical formed following photolytic cleavage. This is proposed to be due to the competitive rates of radical recombination and thiyl radical degradation, and has implications on the choice of monomer (as monomer propagation requires reinitiation of the oligomeric/polymeric RAFT agent). These findings can provide guidelines and increase understanding when conducting a photopolymerization employing thiocarbonylthio RAFT agents. † Electronic supplementary information (ESI) available: Materials and characterization details. Experimental procedures and supplementary figures. See