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Author: Melnyk, Inga × DDC: 540 × Type: Article × WGL Institute: IPF ×

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Now showing 1 - 3 of 3
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    Bioinspired Polydopamine Coating as an Adhesion Enhancer Between Paraffin Microcapsules and an Epoxy Matrix
    (Washington, DC : ACS Publications, 2020) Fredi, Giulia; Simon, Frank; Sychev, Dmitrii; Melnyk, Inga; Janke, Andreas; Scheffler, Christina; Zimmerer, Cordelia
    Microencapsulated phase change materials (PCMs) are attracting increasing attention as functional fillers in polymer matrices, to produce smart thermoregulating composites for applications in thermal energy storage (TES) and thermal management. In a polymer composite, the filler–matrix interfacial adhesion plays a fundamental role in the thermomechanical properties. Hence, this work aims to modify the surface of commercial PCM microcapsules through the formation of a layer of polydopamine (PDA), a bioinspired polymer that is emerging as a powerful tool to functionalize chemically inert surfaces due to its versatility and great adhesive potential in many different materials. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) evidenced that after PDA coating, the surface roughness increased from 9 to 86 nm, which is beneficial, as it allows a further increase in the interfacial interaction by mechanical interlocking. Spectroscopic techniques allowed investigating the surface chemistry and identifying reactive functional groups of the PDA layer and highlighted that, unlike the uncoated microcapsules, the PDA layer is able to react with oxirane groups, thereby forming a covalent bond with the epoxy matrix. Hot-stage optical microscopy and differential scanning calorimetry (DSC) highlighted that the PDA modification does not hinder the melting/crystallization process of the paraffinic core. Finally, SEM micrographs of the cryofracture surface of epoxy composites containing neat or PDA-modified microcapsules clearly evidenced improved adhesion between the capsule shell and the epoxy matrix. These results showed that PDA is a suitable coating material with considerable potential for increasing the interfacial adhesion between an epoxy matrix and polymer microcapsules with low surface reactivity. This is remarkably important not only for this specific application but also for other classes of composite materials. Future studies will investigate how the deposition parameters affect the morphology, roughness, and thickness of the PDA layer and how the layer properties influence the capsule–matrix adhesion.
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    Toward Artificial Mussel-Glue Proteins: Differentiating Sequence Modules for Adhesion and Switchable Cohesion
    (Weinheim : Wiley-VCH, 2020) Arias, Sandra; Amini, Shahrouz; Horsch, Justus; Pretzler, Matthias; Rompel, Annette; Melnyk, Inga; Sychev, Dmitrii; Fery, Andreas; Börner, Hans G.
    Artificial mussel-glue proteins with pH-triggered cohesion control were synthesized by extending the tyrosinase activated polymerization of peptides to sequences with specific modules for cohesion control. The high propensity of these sequence sections to adopt β-sheets is suppressed by switch defects. This allows enzymatic activation and polymerization to proceed undisturbed. The β-sheet formation is regained after polymerization by changing the pH from 5.5 to 6.8, thereby triggering O→N acyl transfer rearrangements that activate the cohesion mechanism. The resulting artificial mussel glue proteins exhibit rapid adsorption on alumina surfaces. The coatings resist harsh hypersaline conditions, and reach remarkable adhesive energies of 2.64 mJ m−2 on silica at pH 6.8. In in situ switch experiments, the minor pH change increases the adhesive properties of a coating by 300 % and nanoindentation confirms the cohesion mechanism to improve bulk stiffness by around 200 %. © 2020 The Authors. Published by Wiley-VCH GmbH
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    Polymerizing Like Mussels Do: Toward Synthetic Mussel Foot Proteins and Resistant Glues
    (Weinheim : Wiley-VCH, 2018) Horsch, Justus; Wilke, Patrick; Pretzler, Matthias; Seuss, Maximilian; Melnyk, Inga; Remmler, Dario; Fery, Andreas; Rompel, Annette; Börner, Hans G.
    A novel strategy to generate adhesive protein analogues by enzyme-induced polymerization of peptides is reported. Peptide polymerization relies on tyrosinase oxidation of tyrosine residues to Dopaquinones, which rapidly form cysteinyldopa-moieties with free thiols from cysteine residues, thereby linking unimers and generating adhesive polymers. The resulting artificial protein analogues show strong adsorption to different surfaces, even resisting hypersaline conditions. Remarkable adhesion energies of up to 10.9 mJ m−2 are found in single adhesion events and average values are superior to those reported for mussel foot proteins that constitute the gluing interfaces.