Front Cover: Rigid Multidimensional Alkoxyamines: A Versatile Building Block Library (Eur. J. Org. Chem. 2/2021)

Matt, Yannick; Wessely, Isabelle; Gramespacher, Lisa; Tsotsalas, Manuel; Bräse, Stefan

doi:10.1002/ejoc.202001622

Cited by 1 publication

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“…[10] To this aim, we developed isoindoline and TEMPO-based multi-fold nitroxides (e.g., tetranitroxide) and (polymeric) alkoxyamine building blocks, that can be directly utilized for the construction of CANs with alkoxyamine bonds through the dynamic nitroxideexchange reaction. [72,73] The dynamic equilibrium in the NER allows for adjustment of the crosslinking degree or complete dissolution of the networks by adding an excess amount of mononitroxide. After decrosslinking, linear polymers, and tetranitroxide building blocks remain and can be fully recycled.…”

Section: Recyclability and Reprocessabilitymentioning

confidence: 99%

“…We extended this concept in the development of network structures based on discrete molecular building blocks with tunable crosslinking degrees and mechanical properties ranging from soft and gel-like to rigid and highly porous. [71][72][73] In such nitroxide exchange networks, the dynamic nature of the NER allows the modulation of properties by shifting the equilibrium state of the reaction and imparts self-healing characteristics and recyclability (sol-gel-sol phase) to the networks. [71] Besides, the connecting alkoxyamine moieties within the networks not only serve as a dynamic bond, providing recyclability, but can also be utilized as NMP initiators, in analogy to the work of Otsuka, Takahara, and co-workers, enabling network expansion with precisely controlled molecular weight.…”

Section: Cans Based On Dynamic Alkoxyamine Bondsmentioning

confidence: 99%

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Covalent Adaptable Networks Based on Dynamic Alkoxyamine Bonds

Jia

Delaittre

Tsotsalas

2022

Macro Materials & Eng

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Covalent adaptable networks (CANs) introduce a new paradigm to polymer science, by making static network polymers dynamic and thereby recyclable, reprocessable, and self‐healing. The critical feature in CANs is the presence of dynamic covalent linkages within the network structure. A variety of such linkages are introduced into CANs, making the respective networks responsive to various stimuli, such as light, temperature, or pH. Here, CANs based on alkoxyamines as dynamic covalent bonds are reviewed. Alkoxyamines uniquely combine the ability to dynamically form, break, and reform covalent bonds with the possibility to initiate reversible‐deactivation radical polymerization. Polymer networks based on alkoxyamines are therefore both adaptive and quasi‐living, able to remodel the network structure by nitroxide‐exchange reactions (NER) and extend the network structure by nitroxide‐mediated polymerization (NMP). In this review, the concepts behind CANs are first introduced and the properties of nitroxides and derived alkoxyamines are discussed. A special focus is set on the ability to tune the response of alkoxyamines to different stimuli, through alteration of their structure. In addition, possible side reactions during dynamic bond exchange and limitations for polymerization are critically reviewed. Subsequently, examples of alkoxyamine‐based CANs responsive to different stimuli, such as temperature, light, or chemical triggers, are discussed. Properties and applications of CANs based on alkoxyamines are then discussed. Finally, an outlook is provided on challenges that need to be addressed as well as opportunities that lie within these “living” CANs.

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Section: Recyclability and Reprocessabilitymentioning

confidence: 99%