Materialien für die “Ewigkeit”: selbstheilende Polymere – auch rezyklierbar!

Marinow, A. et. al., Chemie in unserer Zeit, ASAP, 2021, ciuz.202100014R1

Wie man die Lebensdauer von Materialien verlängern kann hat die Menschheit nicht erst im 21. Jahrhundert beschäftigt. So hat der Begriff „Verlängerung der Nutzungsdauer eines Materials“ zusätzlich Bedeutung vor allem im Bereich der Konsumprodukte erhalten, nicht zuletzt über den Wunsch der Vermeidung von Müll und von emittierten Kohlenstoffdioxid. Die Nutzung von reversiblen chemischen Bindungen erlaubt es Polymermaterialien mit selbstheilenden Eigenschaften herzustellen, aber auch neue Konzepte der Rezyklierung/ Wiederverwendung von Polymeren zu ermöglichen – damit kann die Nutzungsdauer von Batterien, Solarzellen, Mobiltelefonen oder Gummireifen verlängert werden.

Selfdiagnostic Polymers – Inline Detection of Thermal Degradation of Unsaturated Poly(ester imide)s

Funtan, A. et. al., Advanced Materials, 2021, https://doi.org/10.1002/adma.202100068

Modern electro-engines are based on resins constituted from poly(esterimides) (PEI), isolating and mechanically separating the copper-wires in enamels. We here report a novel, inline-chemical reporting system to monitor thermal degradation of such thermoset-systems by simple solid state fluorescence measurements, thus allowing to prevent short circuits and thus primoridal destruction of the device. © 2021 The Authors. Advanced Materials published by Wiley‐VCH GmbH

Terminal flow of cluster-forming supramolecular polymer networks – single-chain relaxation or micelle reorganization?

Mordvinkin, A. et. al., Phys. Rev. Lett. 2020, 125, 127801, https://journals.aps.org/prl/accepted/6907cYe2G6b10f7bf0d70da94c6a3d21a2892f6e5

We correlate the terminal relaxation of supramolecular polymer networks, based on unentangled telechelic poly(isobutylene) linear chains forming micellar end-group clusters, with the the microscopic chain dynamics as probed by proton NMR. For a series of samples with increasing molecular weight, we find a quantitative agreement between the terminal relaxation times and their activation energies provided by rheology and NMR validating the transient network model and the special case of the sticky Rouse model, and dismissing more dedicated approaches treating the terminal relaxation in terms of micellar rearrangements. Copyright © 2020 by American Physical Society.

The “labile” chemical bond: A perspective on mechanochemistry in polymers.

Binder, W. H. Polymer 2020, 122639, DOI: https://doi.org/10.1016/j.polymer.2020.122639.

Currently noncovalent bonds are ranked equally important to their covalent counterparts, in particular in view of controlling macromolecules structure and assembly by pure force. With Staudinger’s work expanded by mechanically driven bond-rupture in macromolecules, applications of mechanophores are highlighted in view of interfaces, stress-detection, vitrimers and self-healing. Reproduced with permission. Copyright 2020© Elsevier B. V.

Detection of stress in polymers: mechanochemical activation of CuAAC click reactions in poly(urethane) networks.

Biewend, M., et al. Soft Matter 2020, 16 (5), 1137-1141, DOI: http://dx.doi.org/10.1039/C9SM02185J.

We report on copper(i)-bis(N-heterocyclic carbene)s (NHC) for quantitative stress-sensing, embedded within polyurethane networks, triggering a fluorogenic copper(i) azide alkyne cycloaddition (CuAAC) of 8-azido-2-naphtol and 3-hydroxy phenylacetylene. A completely transparent, force responsive poly(urethane) material is generated, allowing a quantification of the applied stress. Reproduced with permission of The Royal Society of Chemistry.

Vitrimers: Associative dynamic covalent adaptive networks in thermoset polymers.

Krishnakumar, B., et al. Chemical Engineering Journal 2020,385, 123820,DOI: https://doi.org/10.1016/j.cej.2019.123820.

The vitrimer-thermoset concept represents an important contribution to improve the durability and recyclability of thermoset-systems. The concept of Associative Dynamic Covalent Adaptive Networks (ADCAN), based on thermosetting vitrimers,demonstrates a high level of stress relaxation, self-healing and shape memory properties. This review article describes the relevant associative dynamic covalent exchange reaction mechanisms for vitrimers within thermosetting polymers and summarizes the resulting material properties with a final focus on recent applications. Reproduced with permission. Copyright 2019© Elsevier B. V.

Catalyst free self-healable vitrimer/graphene oxide nanocomposites.

Krishnakumar, B., et al. Composites Part B: Engineering 2020, 184, 107647,DOI: https://doi.org/10.1016/j.compositesb.2019.107647.

Catalyst free graphene oxide (GO) promoted self-healing vitrimer nanocomposites are designed, where the synthesized vitrimer nanocomposites displays self-healing properties via disulfide exchange based covalent adaptive network behavior. This study found that GO based nanofiller enhance the self-healing properties, including the shape memory and flexural strength of the materials. The GO induced lower glass transition was helpful to achieve low temperature self-healing: when compared to epoxy vitrimers (73% and 60% self-healing) the vitrimeric nanocomposites demonstrates a 88% and 80% self-healing for the first and second cycle, respectively. Reproduced with permission. Copyright 2019© Elsevier B. V.

Functional structural nanocomposites with integrated self-healing ability.

Guadagno, L., et al. Materials Today: Proceedings 2020 DOI: https://doi.org/10.1016/j.matpr.2020.03.051.

The use of aeronautical thermosetting resins in the field of structural materials is still limited because of several drawbacks, such as the absence of electrical and thermal conductivity and the poor impact damage resistance. An important contribution for increasing the composite application in this field can be given by implementing a strategy of autonomous damage-repair and other specific functions integrated into the material structure. This work proposes a successful strategy based on the design of supramolecular self-healing systems. It is aimed at developing self-healing, load-bearing structures with all functionalities integrated into a single material able to fulfill important industrial requirements. Reproduced with permission. Copyright 2020© Elsevier B. V.

Biomimetic Elastin-Like Polypeptides as Materials for the Activation of Mechanophoric Catalysts.

Funtan, S., et al. Organic Materials 2020, 2, 116-128,DOI: https://doi.org/10.1055/s-0040-1702149.

Elastin-like polypeptides (ELPs) are well known for their elastic and thermoresponsive behaviors. Here, the synthesis of ELPs of varying chain lengths and their coupling to a mechanoresponsive catalyst are reported. Mechanochemical activation of the synthesized catalysts by an external applied force, showed conversions of the copper(I)-catalyzed alkyne-azide “click” reaction (CuAAC) up to 5.6% with an increasing chain length of the peptide. Reproduced with permission. Copyright 2020© Georg Thieme Verlag KG, Germany.

Synthesis of polymer-linked copper(i) bis(N-heterocyclic carbene) complexes of linear and chain extended architecture.

B iewend, M., et al. Polymer Chemistry 2019, 10 (9), 1078-1088, DOI: http://dx.doi.org/10.1039/C8PY01751D.

Here a novel synthetic approach towards poly(styrene) (PS)-based copper(i) bis(NHC) complexes with linear and chain extended different architectures and their defined activation for CuAAC by mechanical force is reported. A mechanochemical activation of these complexes is demonstrated in bulk quantifying the catalytic activity in a fluorogenic CuAAC click reaction with conversions up to 44%, which allows the use of these polymers as stress-sensors. Reproduced with permission of The Royal Society of Chemistry.