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Review
. 2017 Dec 29;10(1):35.
doi: 10.3390/polym10010035.

Metal Free Reversible-Deactivation Radical Polymerizations: Advances, Challenges, and Opportunities

Johannes Kreutzer  1 , Yusuf Yagci  2   3
Affiliations
Review

Metal Free Reversible-Deactivation Radical Polymerizations: Advances, Challenges, and Opportunities

Johannes Kreutzer et al. Polymers (Basel). .

Abstract

A considerable amount of the worldwide industrial production of synthetic polymers is currently based on radical polymerization methods. The steadily increasing demand on high performance plastics and tailored polymers which serve specialized applications is driven by the development of new techniques to enable control of polymerization reactions on a molecular level. Contrary to conventional radical polymerization, reversible-deactivation radical polymerization (RDRP) techniques provide the possibility to prepare polymers with well-defined structures and functionalities. The review provides a comprehensive summary over the development of the three most important RDRP methods, which are nitroxide mediated radical polymerization, atom transfer radical polymerization and reversible addition fragmentation chain transfer polymerization. The focus thereby is set on the newest developments in transition metal free systems, which allow using these techniques for biological or biomedical applications. After each section selected examples from materials synthesis and application to biomedical materials are summarized.

Keywords: ATRP; NMRP; RAFT; organic synthesis; polymer chemistry; reversible-deactivation radical polymerization.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1
The most common mechanisms for reversible activation in polymerization reactions.
Scheme 2
Scheme 2
General scheme of the reaction mechanism in NMRP.
Scheme 3
Scheme 3
Initiation mechanism of uni- and bimolecular initiators in NMRP.
Chart 1
Chart 1
TEMPO derivatives used as nitroxides in NMRP.
Chart 2
Chart 2
Alkoxyamines and nitroxide derivatives showing improved bond hydrolysis. Ring enlargement in TEMPO derivatives (N6 and N7) and acyclic nitroxides (N8–N10).
Chart 3
Chart 3
Alkoxyamines bearing stereo centers used in NMRP.
Chart 4
Chart 4
Nitroxides and alkoxyamines used for the RDRP of MMA in NMRP.
Chart 5
Chart 5
Alkoxyamines for pH triggered C–ON bond homolysis used in NMRP.
Chart 6
Chart 6
Functional alkoxyamines used in NMRP.
Scheme 4
Scheme 4
Activation and deactivation equilibrium reaction in ATRP.
Scheme 5
Scheme 5
Schematic depiction of light catalyzed ATRP with Ir(ppy)3 as catalyst.
Scheme 6
Scheme 6
Schematic depiction of the oxidative quenching mechanism in metal free ATRP.
Scheme 7
Scheme 7
Reductive quenching mechanism with N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) as an example for electron sacrificing compound in metal free ATRP.
Scheme 8
Scheme 8
Mechanism of RAFT polymerization.
Chart 7
Chart 7
Typical chain transfer agents used in RAFT.
Scheme 9
Scheme 9
Reaction mechanism for photo-RAFT involving iniferter process.
Scheme 10
Scheme 10
Reaction mechanism for PET-RAFT.
Scheme 11
Scheme 11
Organo catalyzed (OC) PET-RAFT. (a) Oxidative pathway; (b) reductive pathway.
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