TY - JOUR A1 - Cappella, Brunero A1 - Silbernagl, Dorothee T1 - Nanomechanica lProperties of Mechanical Double-Layers: A Novel Semiempirical Analysis N2 - Force-displacement curves have been acquired with a commercial atomic force microscope on a thin film of poly(n-butyl methacrylate) on glass substrates. The film thickness is nonuniform, ranging in the measured area from 0 to 30 nm, and gives the possibility to survey the so-called "mechanical double-layer" topic, i.e., the influence of the substrate on the mechanical properties of the film in dependence of the film thickness. The stiffness and the deformation for each force-distance curve were determined and related to the film thickness. We were able to estimate the resolution of the film thickness that can be achieved by means of force-distance curves. By exploiting the data acquired in the present and in a previous experiment, a novel semiempirical approach to describe the mechanical properties of a mechanical double-layer is introduced. The mathematical model, with which deformation-force curves can be described, permits to calculate the Young's moduli of film and substrate in agreement with literature values and to determine the film thickness in agreement with the topography. PY - 2007 U6 - https://doi.org/10.1021/la701234q SN - 0743-7463 SN - 1520-5827 VL - 23 IS - 21 SP - 10779 EP - 10787 PB - American Chemical Society CY - Washington, DC AN - OPUS4-17808 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cappella, Brunero A1 - Silbernagl, Dorothee T1 - Nanomechanical properties of polymer thin films measured by force-distance curves N2 - Force–displacement curves have been acquired with a commercial atomic force microscope on thin films of poly(n-butyl methacrylate) on glass substrates. Different film thicknesses, from 10 up to 430 nm, were chosen to examine in detail the so called “mechanical double-layer” topic, i.e., the influence of the substrate on the determination of the mechanical properties of thin films. Taking advantage of the Hertz theory we calculated for all films the contact radius between tip and sample as a function of the applied load. Further Young's modulus of the samples was derived from the experimental data as a function of the applied load and, alternatively, of the deformation. The results of this analysis for 10 different film thicknesses were fitted with several half empirical equations proposed by several researchers. The focus of this work is to evaluate such existing half empirical theories for mechanical double-layers and to show the need for an alternative consistent approach. KW - Atomic force microscopy KW - Polymer thin films KW - Indentation KW - Young´s modulus PY - 2008 U6 - https://doi.org/10.1016/j.tsf.2007.09.042 SN - 0040-6090 VL - 516 IS - 8 SP - 1952 EP - 1960 PB - Elsevier CY - Amsterdam AN - OPUS4-17809 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silbernagl, Dorothee A1 - Sturm, Heinz A1 - Plajer, A. J. T1 - Thioanhydride/isothiocyanate/epoxide ring-opening terpolymerisation: sequence selective enchainment of monomer mixtures and switchable catalysis N2 - We report a new sequence selective terpolymerisation in which three monomers (butylene oxide (BO) A, PhNCS B and phtalic thioanhydride (PTA) C) are selectively enchained into an (ABA′C)n sequence. PTA/PhNCS/BO ring-opening terpolymerisation ROTERP can be coupled with CS2 ROTERP to generate tetrapolymers and with εDL ROP in switchable catalysis for blockpolymer synthesis. KW - Blockcopolymer KW - 1H-NMR KW - TGA KW - DSC KW - AFM PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-552339 SP - 1 EP - 5 PB - Royal Society of Chemistry CY - Cambridge, UK AN - OPUS4-55233 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zou, T. A1 - Nonappa, N. A1 - Khavani, M. A1 - Vuorte, M. A1 - Penttilä, P. A1 - Zitting, A. A1 - Valle-Delgado, J. J. A1 - Elert, Anna Maria A1 - Silbernagl, Dorothee A1 - Balakshin, M. A1 - Sammalkorpi, M. A1 - Österberg, M. T1 - Experimental and Simulation Study of the Solvent Effects on the Intrinsic Properties of Spherical Lignin Nanoparticles N2 - Spherical lignin nanoparticles (LNPs) fabricated via nanoprecipitation of dissolved lignin are among the most attractive biomass-derived nanomaterials. Despite various studies exploring the methods to improve the uniformity of LNPs or seeking more application opportunities for LNPs, little attention has been given to the fundamental aspects of the solvent effects on the intrinsic properties of LNPs. In this study, we employed a variety of experimental techniques and molecular dynamics (MD) simulations to investigate the solvent effects on the intrinsic properties of LNPs. The LNPs were prepared from softwood Kraft lignin (SKL) using the binary solvents of aqueous acetone or aqueous tetrahydrofuran (THF) via nanoprecipitation. The internal morphology, porosity, and mechanical properties of the LNPs were analyzed with electron tomography (ET), small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), and intermodulation AFM (ImAFM). We found that aqueous acetone resulted in smaller LNPs with higher uniformity compared to aqueous THF, mainly ascribing to stronger solvent−lignin interactions as suggested by MD simulation results and confirmed with aqueous 1,4-dioxane (DXN) and aqueous dimethyl sulfoxide (DMSO). More importantly, we report that both LNPs were compact particles with relatively homogeneous density distribution and very low porosity in the internal structure. The stiffness of the particles was independent of the size, and the Young’s modulus was in the range of 0.3−4 GPa. Overall, the fundamental understandings of LNPs gained in this study are essential for the design of LNPs with optimal performance in applications. KW - Lignin KW - Electron tomography KW - Intermodulation AFM KW - Modulus KW - SAXS PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-546948 SN - 1520-5207 VL - 125 IS - 44 SP - 12315 EP - 12328 PB - ACS AN - OPUS4-54694 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cano Murillo, Natalia A1 - Ghasem Zadeh Khorasani, Media A1 - Silbernagl, Dorothee A1 - Emamverdi, Farnaz A1 - Cacua, K. A1 - Hodoroaba, Vasile-Dan A1 - Sturm, Heinz T1 - Carrier Fibers for the Safe Dosage of Nanoparticles in Nanocomposites: Nanomechanical and Thermomechanical Study on Polycarbonate/Boehmite Electrospun Fibers Embedded in Epoxy Resin N2 - The reinforcing effect of boehmite nanoparticles (BNP) in epoxy resins for fiber composite lightweight construction is related to the formation of a soft but bound interphase between filler and polymer. The interphase is able to dissipate crack propagation energy and consequently increases the fracture toughness of the epoxy resin. Usually, the nanoparticles are dispersed in the resin and then mixed with the hardener to form an applicable mixture to impregnate the fibers. If one wishes to locally increase the fracture toughness at particularly stressed positions of the fiber-reinforced polymer composites (FRPC), this could be done by spraying nanoparticles from a suspension. However, this would entail high costs for removing the nanoparticles from the ambient air. We propose that a fiber fleece containing bound nanoparticles be inserted at exposed locations. For the present proof-of-concept study, an electrospun polycarbonate nonwoven and taurine modified BNP are proposed. After fabrication of suitable PC/EP/BNP composites, the thermomechanical properties were tested by dynamic mechanical analysis (DMA). Comparatively, the local nanomechanical properties such as stiffness and elastic modulus were determined by atomic force microscopy (AFM). An additional investigation of the distribution of the nanoparticles in the epoxy matrix, which is a prerequisite for an effective nanocomposite, is carried out by scanning electron microscopy in transmission mode (TSEM). From the results it can be concluded that the concept of carrier fibers for nanoparticles is viable. KW - Advanced materials KW - Electrospun nanocomposite fiber KW - Nanomechanical charecteisation KW - Nanosafety KW - Epoxy nanocomposites PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-528265 VL - 11 IS - 6 SP - 1591 PB - MDPI CY - CH - 4020 Basel, Switzerland AN - OPUS4-52826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silbernagl, Dorothee A1 - Sturm, Heinz A1 - Cappella, Brunero T1 - Influence of film-substrate adhesion on the mechanical properties of thin polymer films KW - Adhesion KW - AFM KW - Thin film KW - Mechanical properties KW - Force-distance curves PY - 2009 U6 - https://doi.org/10.1021/la8041007 SN - 0743-7463 SN - 1520-5827 VL - 25 IS - 9 SP - 5091 EP - 5097 PB - American Chemical Society CY - Washington, DC AN - OPUS4-19363 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silbernagl, Dorothee A1 - Cappella, Brunero T1 - Mechanical properties of thin polymer films on stiff substrates N2 - Force–displacement curves have been acquired with a commercial atomic force microscope on thin films of poly(n-butyl methacrylate) on glass substrates in order to examine the so-called 'mechanical double layer' topic, i.e. the influence of the substrate on the mechanical properties of the film in dependence of the film thickness. The hyperbolic fit, a novel semi-empirical equation introduced in previous articles, has been further corroborated. The interpretation of this equation has been deepened, yielding a quantitative and demonstrative characterization of the mechanical properties of double layers. Provided that the Young's moduli of bulk polymer and substrate are measured from the deformation curves, this mathematical model permits to fit the deformation–force curves on the double layers and to determine the thickness of the polymer films in wide range (0–200 nm). KW - Atomic force microscopy KW - Indentation KW - Rheology KW - Polymers KW - Thin films PY - 2010 U6 - https://doi.org/10.1002/sca.20196 SN - 0161-0457 SN - 1932-8745 VL - 32 IS - 5 SP - 282 EP - 293 PB - Wiley CY - Hoboken, NJ AN - OPUS4-22681 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silbernagl, Dorothee A1 - Cappella, Brunero T1 - Reconstruction of a hidden topography by single AFM force-distance curves N2 - Force–distance curves have been acquired with an Atomic Force Microscope on polymethyl methacrylate with embedded glass spheres. The glass spheres provide a stiff substrate with an irregular and complex topography hidden underneath a compliant and even polymer film. This situation is a special case of a mechanical double-layer, which we examined in detail in previous experiments. Up to now uniform and non-uniform polymer films on an even substrate were examined. The film thickness on each point of the sample surface was known and force–distance curves could be averaged in groups according to the film thickness. In this way we were able to develop a semi empirical approach which allows describing the shape of averaged force–distance curves depending on the Young’s moduli of the involved materials and on the film thickness. In this experiment we reconstruct a hidden topography, i.e., we determine the polymer thickness on each point of the sample by analyzing single force–distance curves with our semi empirical equation. The accuracy reached by this approach permits to obtain a reconstruction of the shape and position of the embedded particles limited by a maximum detection depth. Single curves are also analyzed qualitatively in order to locate areas where the adhesion at the polymer/glass interface is weak or the two phases are detached. KW - Atomic Force Microscopy KW - Force-distance curves KW - Composite materials KW - Mechanical properties KW - Interfaces PY - 2009 U6 - https://doi.org/10.1016/j.susc.2009.04.029 SN - 0039-6028 VL - 603 IS - 16 SP - 2363 EP - 2369 PB - Elsevier CY - Amsterdam AN - OPUS4-22682 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fankhänel, J. A1 - Silbernagl, Dorothee A1 - Ghasem Zadeh Khorasani, Media A1 - Daum, B. A1 - Kempe, A. A1 - Sturm, Heinz A1 - Rolfes, R. T1 - Mechanical properties of Boehmite evaluated by Atomic Force Microscopy experiments and Molecular Dynamic Finite Element simulations N2 - Boehmite nanoparticles show great potential in improving mechanical properties of fiber reinforced polymers. In order to predict the properties of nanocomposites, knowledge about the material parameters of the constituent phases, including the boehmite particles, is crucial. In this study, the mechanical behavior of boehmite is investigated using Atomic Force Microscopy (AFM) experiments and Molecular Dynamic Finite Element Method (MDFEM) simulations. Young’s modulus of the perfect crystalline boehmite nanoparticles is derived from numerical AFM simulations. Results of AFM experiments on boehmite nanoparticles deviate significantly. Possible causes are identified by experiments on complementary types of boehmite, that is, geological and hydrothermally synthesized samples, and further simulations of imperfect crystals and combined boehmite/epoxy models. Under certain circumstances, the mechanical behavior of boehmite was found to be dominated by inelastic effects that are discussed in detail in the present work.The studies are substantiated with accompanying X-ray diffraction and Raman experiments. KW - AFM KW - MDFEM KW - Nanocomposite KW - Epoxy KW - X-ray diffraction KW - Raman spectroscopy KW - Young’s modulus KW - Slippage of weakly linked layers PY - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-384230 UR - https://www.hindawi.com/journals/jnm/2016/5017213/#B26 VL - 2016 IS - Article ID 5017213 SP - 1 EP - 13 PB - Hindawi Publishing Corporation AN - OPUS4-38423 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bhattacharya, Biswajit A1 - Michalchuk, Adam A1 - Silbernagl, Dorothee A1 - Rautenberg, Max A1 - Schmid, Thomas A1 - Feiler, Torvid A1 - Reimann, K. A1 - Ghalgaoui, A. A1 - Sturm, Heinz A1 - Paulus, B. A1 - Emmerling, Franziska T1 - A Mechanistic Perspective on Plastically Flexible Coordination Polymers N2 - Mechanical flexibility in single crystals of covalently bound materials is a fascinating and poorly understood phenomenon. We present here the first example of a plastically flexible one-dimensional (1D) coordination polymer. The compound [Zn(m-Cl)2(3,5-dichloropyridine)2]n is flexible over two crystallographic faces. Remarkably, the single crystal remains intact when bent to 1808. A combination of microscopy, diffraction, and spectroscopic studies have been used to probe the structural response of the crystal lattice to mechanical bending. Deformation of the covalent polymer chains does not appear to be responsible for the observed macroscopic bending. Instead, our results suggest that mechanical bending occurs by displacement of the coordination polymer chains. Based on experimental and theoretical evidence, we propose a new model for mechanical flexibility in 1D coordination polymers. Moreover, our calculations propose a cause of the different mechanical properties of this compound and a structurally similar elastic material KW - Coordination polymer KW - Flexible crystals KW - Mechanical properties KW - Plastic deformation PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-504755 VL - 59 IS - 14 SP - 5557 EP - 5561 PB - Wiley-VCH AN - OPUS4-50475 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -