This paper presents a review of living radical polymerization achieved with thiocarbonylthio compounds [ZC(=S)SR] by a mechanism of reversible addition–fragmentation chain transfer (RAFT). Since we first introduced the technique in 1998, the number of papers and patents on the RAFT process has increased exponentially as the technique has proved to be one of the most versatile for the provision of polymers of well defined architecture. The factors influencing the effectiveness of RAFT agents and outcome of RAFT polymerization are detailed. With this insight, guidelines are presented on how to conduct RAFT and choose RAFT agents to achieve particular structures. A survey is provided of the current scope and applications of the RAFT process in the synthesis of well defined homo-, gradient, diblock, triblock, and star polymers, as well as more complex architectures including microgels and polymer brushes.

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Living radical polymerization by the RAFT process

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

Tetrathiafulvalenes, oligoacenenes, and their buckminsterfullerene derivatives: the brick and mortar of organic electronics.

Radical addition-fragmentation chemistry in polymer synthesis

Among the living radical polymerization techniques, reversible addition–fragmentation chain transfer (RAFT) and macromolecular design via the interchange of xanthates (MADIX) polymerizations appear to be the most versatile processes in terms of the reaction conditions, the variety of monomers for which polymerization can be controlled, tolerance to functionalities, and the range of polymeric architectures that can be produced. This review highlights the progress made in RAFT/MADIX polymerization since the first report in 1998. It addresses, in turn, the mechanism and kinetics of the process, examines the various components of the system, including the synthesis paths of the thiocarbonyl-thio compounds used as chain-transfer agents, and the conditions of polymerization, and gives an account of the wide range of monomers that have been successfully polymerized to date, as well as the various polymeric architectures that have been produced. In the last section, this review describes the future challenges that the process will face and shows its opening to a wider scientific community as a synthetic tool for the production of functional macromolecules and materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:5347–5393, 2005

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/pola.20986

Macromolecular design via réversible addition-fragmentation chain transfer (RAFT)/Xanthates (MADIX) polymerization

The analysis of the NOE effects based upon the interproton distances obtained by MM2 calculations yields a quantitative assessment of the conformer population of 1- and 2-naphthaldehydes (Z-conformer 85% and 12% respectively).

The Conformational Preferences of Isomeric Naphthaldehydes as Determined by NOE Experiments.

This paper is aimed at providing an overview of our studies on the title compounds as spin trapping agents, and at emphasising the links between purely cognitive, academic research and industrial applications. Phosphoryl- and thiophosphoryl-dithioformates exhibit a comparable and interesting spin trapping ability, their efficiency being analogous to that of some aromatic thioketones. The spectral hyperfine structure may provide valuable information on the nature of the trapped radical but the phosphorus hfs constant cannot be used as an useful indicator. Thionformates are less efficient spin traps than the corresponding dithioformates, being inert towards stabilised radicals such as benzyl or relatively hindered radicals as tert-butoxyl. In no case could spin adducts to thiolformates be detected, this being an indication that their carbonyl group is significantly deactivated with respect to that of organic and organometallic ketones. Because of their ability in trapping either alkyl or alkoxy radicals both kind of dithioformates were exploited as stabilisers in the processing of such polymers as polypropylene, but their outstanding performance could not compensate for some organoleptic drawbacks that were intrinsic of the thiocarbonyl function. A much more promising application of dithioesters is instead their use as RAFT chain transfer agents in the controlled polymerisation of styrene. Preliminary experiments with benzyl diethoxyphosphoryldithioformate have afforded polystyrene with a polydispersity as low as 1.17, but further studies are needed to fully elucidate the RAFT-polymerisation mechanism and to optimise its outcome.

Phosphoryl and Thiophosphoryldithioformates as Spin Traps: From EPR Studies to Practical Applications

The radical anions from thiobenzophenone, thiobenzoyltriphenylsilane, and 3,5-di-tert-butylthiobenzoyltriphenylsilane were detected by EPR spectroscopy when these compounds were reacted with a number of Grignard reagents, RMgBr. The radical adducts resulting from addition of R• radicals to the thiones were also detected. The formation of the radical anions indicates unambiguously the occurrence of a SET process which might be the initial stage of these reactions. In the case of tris(trimethylsilyl)ethanethial only the radical adducts were detected. The first reduction potentials of these thiones have also been measured in order to verify the feasibility of the SET process. In agreement with the EPR experiments, the calculated standard free energy changes suggest that electron transfer is possible in the first three cases and disfavored with the thioaldehyde.

Reactions Between Grignard Reagents and Thiocarbonyl Compounds: A Revisitation.

Conformational Studies by Dynamic NMR. Part 34. Stereomutation and Torsional Processes in Aromatic Tertiary Amines.

The radical cation and anion of the title compound were obtained either by treatment with mercury trifluorocatetate in trifluoroacetic acid or by reduction with potassium in tetrahydrofurane. For both species the ESR spectra indicated magnetic non-equivalence of the two phosphorus atoms, as well as of the two methyl groups. Spectra attributed to the corresponding spin adducts were also observed when reacting the title compound with in situ-generated alkoxyl and thiyl radicals. MO calculations carried out for both the ionic radicals and the neutral spin adducts led to questioning the actual nature of some of the latter species.

Dante Macciantelli

Papers

The Conformational Preferences of Isomeric Naphthaldehydes as Determined by NOE Experiments.

Phosphoryl and Thiophosphoryldithioformates as Spin Traps: From EPR Studies to Practical Applications

Reactions Between Grignard Reagents and Thiocarbonyl Compounds: A Revisitation.

Conformational Studies by Dynamic NMR. Part 34. Stereomutation and Torsional Processes in Aromatic Tertiary Amines.

Radical ions from and spin adducts to 1,2-dimethyl-3,4-bis[(2,4,6-tri-tert-butylphenyl) phosphinidene]-1-cyclobutene