Browsing by Subject "Self-healing"

Now showing 1 - 2 of 2

Open Access
Bioaromatic-associated multifunctionality in lignin-containing reversible elastomers
(American Chemical Society, 2023-07-12) Thys, Marlies; Kaya, Görkem Eylül; Soetemans, Lise; Van Assche, Guy; Bourbigot, Serge; Baytekin, Bilge; Vendamme, Richard; Van den Brande, Niko
The unique molecular structure of lignin, intrinsically rich in bioaromatic groups (phenolic hydroxyls), gives it, e.g., antioxidant, antistatic, antimicrobial, UV-blocking, hydrophobic, or even flame-retardant properties, which are highly interesting. An attractive strategy to use lignin as a macro-monomer for the design of functional materials that retain certain of these lignin-specific properties is to partially preserve some phenolic groups during the synthesis. In this work, we explore the properties of reversible elastomers containing a lignin fraction whose phenolic groups have only been partially modified. To do so, Kraft lignin was first fractionated and partially (89%) modified with furan groups, allowing its homogeneous incorporation in Diels-Alder formulations. The effect of the residual phenolic groups embedded in the polymer matrix was then systematically studied, focusing on the specific material properties associated with lignin. The obtained lignin-containing networks notably showed increased radical scavenging activity (which directly resulted in improved antistatic and antioxidant properties), displayed improved UV absorbance due to the presence of multiple lignin chromophores, and were even able to inhibit the growth of bacteria. This article demonstrates that tailored and partially modified lignin fractions could be used as multi-functional building blocks for the design of complex (and reversible) polymer architectures, mimicking some of the unique lignin functionalities found in nature, and this without the need to add specific additives.
Open Access
Characterization of self-assembly and self-healing of peptide amphiphiles by atomic force microscopy
(2017-10) Dikeçoğlu, Fatma Begüm
Biological feedback mechanisms exert precise control over the initiation and termination of molecular self-assembly in response to environmental stimuli, while minimizing the formation and propagation of defects through self-repair processes. Peptide amphiphile (PA) molecules can self-assemble at physiological conditions to form supramolecular nanostructures that structurally and functionally resemble the nanofibrous proteins of the extracellular matrix (ECM), and their ability to reconfigure themselves in response to external stimuli is crucial for the design of intelligent systems. In this thesis, we investigated the real-time self-assembly, deformation, and self-healing of ECM-mimetic PA nanofibers in aqueous solution by using a force-stabilizing double-pass scanning AFM imaging method to disrupt the self-assembled peptide nanofibers in a force-dependent manner. We showed that nanofiber damage occurs at tip forces exceeding 1 nN, and that the damaged fibers subsequently recover under sub-nN tip forces. Fiber ends occasionally failed to reconnect following breakage and continue to grow as two individual nanofibers. Energy minimization calculations of nanofibers with increasing cross-sectional ellipticity (corresponding to varying levels of tip-induced fiber deformation) supported our observations, with high-ellipticity nanofibers exhibiting lower stability compared to their non-deformed counterparts. As a result, tip-mediated mechanical forces can provide an effective means of altering nanofiber integrity and visualizing the self-recovery of PA assemblies.