Research Field 2

Shinde, K.S. et.al., Macromol. Chem. Phys., 2023, 2300297, https://doi.org/10.1002/macp.202300297

Here, a mechanochemically triggered Cu(I) bis(N-heterocyclic carbene [NHC))-based metal–organic framwork (MOF) embedded into a thermoplastic polyurethane (TPU)-matrix is reported. The induced fluorogenic copper-catalyzed azide–alkyne cycloaddition (CuAAC) reveals the stressed parts within the thermoplastic PU via a simple optical detection. As determined via oscillating tensile rheology on dumbbell-shaped samples of TPU, a MOF, containing 4.66% copper, catalyzes the fluorogenic CuAAC between the nonfluorescent precursor dyes, 8-azidonaphthalen-2-ol, and 3-hydroxyphenylacetylene. After mechanical activation of the MOF situated inside the TPU, the fluorescent 8-(4-(3-hydroxyphenyl)-1,2,3-triazol-1-yl)naphthalen-2-ol dye is formed. Monitoring the formation of the dye inside the TPU via fluorescence spectrometry at λ_ex = 458 nm shows an increase of the fluorescence intensity up to 60–70%. It is demonstrated that a dumbbell-shaped TPU, subjected to higher stress, displays higher fluorescence than the surrounding other areas, thus effectively functioning as a three-in-one stress-sensor system.

Ucak, Ö. et al., Macromolecular Chemistry and Physics, 2022, 2200344,

https://doi.org/10.1002/macp.202200344

The synthesis of well-defined homo- and co-polypeptides of L-alanine (L-Ala) by ring-opening polymerization (ROP) of its N-carboxyanhydride (NCAs), either via suspension/interfacial- or solution phase-polymerization using 10-undecene-1-amine and α,ω-diamino poly(ethylene glycol) (8 or 1.5 kDa) as primary amine initiators is reported. Subsequently, the folding of the homo- and triblock amphiphilic co-polypeptides under a variety of parameters such as temperature, chain length, and backbone composition and the further transitions of these secondary structures are investigated in HFIP and HFIP-H₂O mixtures via circular dichroism (CD) spectroscopy. A solvent induced helical switch from a 3₁₀-helix to a α-helix when changing from HFIP to HFIP–water mixtures is observed, with water inducing helicity stronger in both, homo-polyalanine and poly(alanine)-PEG-poly(alanine) triblock copolymers. © 2022 The Authors. Macromolecular Chemistry and Physics published by Wiley‐VCH GmbH.

Siva Prasanna Sanka, R. V. et al., Soft Matter, 2023, 98-105,

https://doi.org/10.1039/D2SM01423H

N-doped graphene stabilized Cu(I)-catalyzed self-healing nanocomposites are developed, demonstrating the use of N-doped graphene as both a nanostructured material for enhancing mechanical and conductive properties to trigger self-healing via “click chemistry”. Due to an increase in electron density on nitrogen atom doping, including the coordination of N-doped rGO with Cu⁺ ions, nitrogen-doped graphene-supported copper particles demonstrate a higher reaction yield at room temperature without adding any external ligand/base. Tensile measurements were also performed using molecular dynamics (MD) simulations to support the findings. Given the enormous importance of autonomic repair of materials damage, this concept here reports a trustworthy and reliable chemical system with a high level of robustness. Published with a permission of the Royal Society of Chemistry 2023.

Sharma, H. et al., RSC Advances, 2022, 32569-32582,

http://dx.doi.org/10.1039/D2RA05103F

To achieve sustainable development goals, approaches towards the preparation of recyclable and healable polymeric materials is highly attractive. Self-healing polymers and thermosets based on bond-exchangeable dynamic covalent bonds, so called “vitrimers” could be a great effort in this direction. In order to match the industrial importance, enhancement of mechanical strength without sacrificing the bond exchange capability is a challenging issue, however, such concerns can be overcome through the developments of fiber-reinforced vitrimer composites. This article covers the outstanding features of fiber-reinforced vitrimer composites, including their reprocessing, recycling and self-healing properties, together with practical applications and future perspectives of this unique class of materials. Published with a permission of the Royal Society of Chemistry 2022.

Chenming Li , et al. Polymers, 2022, 14, 4090, DOI: https://doi.org/10.3390/polym14194090

Within the era of battery technology, the urgent demand for improved and safer electrolytes is immanent. In this work, novel electrolytes, based on pyrrolidinium-bistrifluoromethanesulfonyl-imide polymeric ionic liquids (POILs), equipped with quadrupolar hydrogen-bonding moieties of ureido-pyrimidinone (UPy) to mediate self-healing properties are generated. The polymers display good conductivities as well as a self-healing efficiency of up to 88 %, in turn evidencing a rational design of self-healing electrolytes bearing, both hydrogen bonding moieties and low-molecular-weight polymeric ionic liquids.

Krishnan, B. P., et al. Polymers, 2022, DOI:https://doi.org/10.3390/polym14122456

Vitrimers are crosslinked polymeric materials that behave like fluids when heated, regulated by the kinetics of internal covalent bond-exchange, making these materials readily reprocessable and recyclable. We report two novel multiphase vitrimeric materials prepared by the cross-linking of two polymers, namely poly(triethylene glycol sebacate) and poly(2-hydroxyethyl acrylate), using zinc acetate or tin(II) 2-ethylhexanoate as catalysts, which exhibit significantly low Tv temperatures of 39 °C and 29 °C, respectively. The design of such multiphase vitrimers is not only useful for the practical application of vitrimers to reduce plastic waste but could also facilitate further development of functional polymer materials that can be reprocessed at low temperatures.

Binder, W. H., et al. Nachrichten aus der Chemie., 2022, DOI:https://doi.org/10.1002/nadc.20224120686   

Während des Betriebes von Elektromotoren führen thermischen Alterungsprozesses in den PEI-Imprägnierungen zur Freisetzung von als Hauptabbauprodukte, die als nucleophile Analyten für trifluoroacetyl funktionalisierte Stilbene fungieren. Es wurde ein optisches Inline-Detektionssystem entwickelt, um zukünftig unnötige Motorenwechsel zu verhindern und, mit Blick auf die zunehmende Elektromobilität, einen wertvollen Beitrag zur Nachhaltigkeit zu leisten.

Shinde, K., et al. Polymers, 2022, DOI:https://doi.org/10.1002/macp.202200207

Porous coordination polymers, more commonly known as metal-organic frameworks (MOFs), are constructed from metal ions and organic linkers which form a robust network-like structure similar to very dense polymeric networks. We report on the mechanochemical activation of a MOF linking a mechanochemically triggered copper-catalyzed azide-alkyne cycloaddition (CuAAC) with an NHC-MOF. A Cu(I) bis(NHC) is embedded into the MOF analogous to ([Zn₄O{Cu(L)₂}₂]) using the organic bis-NHC ligand, in turn triggering a CuAAC with conversions up to 26.5%. With this knowledge in solution, there are prospects to transfer this mechanochemical activity into polymer networks with embedded MOFs to detect stress in hybrid materials.

Sammon, M. S., et al. Chem Eur. J., 2021, DOI:https://doi.org/10.1002/chem.202100555 and https://doi.org/10.1002/chem.202101683

Point break: A latent copper-biscarbene mechanocatalyst becomes active when a ligand is forcefully removed. Pulling with around 2 nN breaks the copper-carbon bond, as measured by single-molecule force spectroscopy. To be able to assign the bond rupture event to the Cu−C bond, mechanophores with two different lengths of safety-line were specifically synthesized for use in this AFM experiment.