This paper provides a third update to the review of reversible deactivation radical polymerization (RDRP) achieved with thiocarbonylthio compounds (ZC(=S)SR) by a mechanism of reversible addition-fragmentation chain transfer (RAFT) that was published in June 2005 (Aust. J. Chem. 2005, 58, 379). The first update was published in November 2006 (Aust. J. Chem. 2006, 59, 669) and the second in December 2009 (Aust. J. Chem. 2009, 62, 1402). This review cites over 700 publications that appeared during the period mid 2009 to early 2012 covering various aspects of RAFT polymerization which include reagent synthesis and properties, kinetics and mechanism of polymerization, novel polymer syntheses, and a diverse range of applications. This period has witnessed further significant developments, particularly in the areas of novel RAFT agents, techniques for end-group transformation, the production of micro/nanoparticles and modified surfaces, and biopolymer conjugates both for therapeutic and diagnostic applications.

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Living Radical Polymerization by the RAFT Process - A Second Update

Thiol-ene “click” reactions and recent applications in polymer and materials synthesis

Radical addition-fragmentation chemistry in polymer synthesis

The key attribute of the thiol-Michael addition reaction that makes it a prized tool in materials science is its modular “click” nature, which allows for the implementation of this highly efficient, “green” reaction in applications that vary from small molecule synthesis to in situ polymer modifications in biological systems to the surface functionalization of material coatings. Over the past few decades, interest in the thiol-Michael addition reaction has increased dramatically, as is evidenced by the number of studies that have been dedicated to elucidating different aspects of the reaction that range from an in-depth analysis aimed at understanding the mechanistic pathways of the reaction to synthetic studies that have examined modifying molecular structures with the aim of yielding highly efficient thiol-Michael reaction monomers. This review examines the reaction mechanisms, the substrates and catalysts used in the reaction, and the subsequent implementation of the thiol-Michael reaction in materials...

The Thiol-Michael Addition Click Reaction: A Powerful and Widely Used Tool in Materials Chemistry

The use of photoinitiated polymerization is continuously growing in industry as reflected by the large number of applications in not only conventional areas such as coatings, inks, and adhesives but also high-tech domains, optoelectronics, laser imaging, stereolithography, and nanotechnology. In this Perspective, the latest developments in photoinitiating systems for free radical and cationic polymerizations are presented. The potential use of photochemical methods for step-growth polymerization is also highlighted. The goal is, furthermore, to show approaches to overcome problems associated with the efficiency, wavelength flexibility, and environmental and safety issues in all photoinitiating systems for different modes of activation. Much progress has been made in the past 10 years in the preparation of complex and nano-structured macromolecules by using photoinitiated polymerizations. Thus, the new and emerging applications of photoinitiated polymerizations in the field of biomaterials, surface modific...

Photoinitiated Polymerization: Advances, Challenges, and Opportunities

The "click" trick: Many reactions are classified as click reactions even though some are limited to certain applications. Thus, there is danger that the term "click" will become meaningless over time and simply a synonym for "successful". To prevent this, the original click criteria are evaluated in this Essay specifically for the synthetic polymer field and a set of criteria are specified that distinguishes click from other efficient reactions. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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"Clicking" Polymers or Just Efficient Linking: What Is the Difference?**

"Clicking" polymers or just efficient linking: What is the difference?

Photomediated controlled radical polymerization

In this work, we report our findings on the use of radical thiol-ene chemistry for polymer–polymer conjugation. The manuscript combines the results from the Preparative Macromolecular Chemistry group from the Karlsruhe Institute of Technology (KIT) and the Polymer Chemistry Research group from Ghent University (UGent), which allowed for an investigation over a very broad range of reaction conditions. In particular, thermal and UV initiation methods for the radical thiol-ene process were compared. In the KIT group, the process was studied as a tool for the synthesis of star polymers by coupling multifunctional thiol core molecules with poly(n-butyl acrylate) macromonomers (MM), employing thermally decomposing initiators. The product purity and thus reaction efficiency was assessed via electrospray ionization mass spectrometry. Although the reactions with 10 or 5 equivalents of thiol with respect to macromonomer were successful, the coupling reaction with a one-to-one ratio of MM to thiol yielded only a fraction of the targeted product, besides a number of side products. A systematic parameter study such as a variation of the concentration and nature of the initiator and the influence of thiol-to-ene ratio was carried out. Further experiments with poly(styrene) and poly(isobornyl acrylate) containing a vinylic end group confirmed that thermal thiol-ene conjugation is far from quantitative in terms of achieving macromolecular star formation. In parallel, the UGent group has been focusing on photo-initiated thiol-ene chemistry for the synthesis of functional polymers on one hand and block copolymers consisting of poly(styrene) (PS) and poly(vinyl acetate) (PVAc) on the other hand. Various functionalization reactions showed an overall efficient thiol-ene process for conjugation reactions of polymers with low molecular weight compounds (∼90% coupling yield). However, while SEC and FT-IR analysis of the conjugated PS-PVAc products indicated qualitative evidence for a successful polymer–polymer conjugation, 1H NMR and elemental analysis revealed a low conjugation efficiency of about 23% for a thiol-to-ene ratio equal to one. Blank reactions using typical thiol-ene conditions indicated that bimolecular termination reactions occur as competitive side reactions explaining why a molecular weight increase is observed even though the thiol-ene reaction was not successful. The extensive study of both research groups indicates that radical thiol-ene chemistry should not be proposed as a straightforward conjugation tool for polymer–polymer conjugation reactions. Head-to-head coupling is a major reaction pathway, which interrupts the propagation cycle of the thiol-ene process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1699–1713, 2010

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Thomas Junkers

Papers

"Clicking" Polymers or Just Efficient Linking: What Is the Difference?**

"Clicking" polymers or just efficient linking: What is the difference?

Photomediated controlled radical polymerization

Limitations of radical thiol-ene reactions for polymer-polymer conjugation

Limitations of radical thiol-ene reaction for polymer-polymer conjugations