Research Field 2

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.

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.

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.

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.

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.

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.

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.

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.

Michael, P., et al. Macromolecular Rapid Communications 2018, 1800376, DOI: https://doi.org/10.1002/marc.201800376.

Strategies for visualizing stress within polymeric materials are of growing interest during the past decade. Stress-sensing materials, triggered by a mechanoresponsive catalytic system based on latent copper(I)bis(N-heterocyclic carbene) mechanophores, are reported. The activation for network-based mechanocatalysts, observing “click” conversions up to 44%, while chain-extended and linear mechanocatalysts activate is detected. The developed catalysts enable “irreversible” mechanochromic systems for stress-sensing devices. Reproduced with permission. Copyright 2018©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Campanella, A., et al. Macromolecular Rapid Communications 2018, 1700739, DOI: http://dx.doi.org/10.1002/marc.201700739.

Adaption and self-healing are two major principles in material science, often coupled with the placement of supramolecular moieties within a material. Basic physicochemical aspects as well as new material developments in the field are described, published after a recent review in Macromolecular Rapid Communications in 2013. Reproduced with permission. Copyright 2018©, WILEY-VCH Verlag GmbH & Co. KGaA,