TY - JOUR
A1 - Stroh, Julia
A1 - Feiler, Torvid
A1 - Ali, N. Z.
A1 - Minas da Piedade, M. E.
A1 - Emmerling, Franziska
T1 - Mechanistic Insights into a Sustainable Mechanochemical Synthesis of Ettringite
N2 - Mechanochemistry offers an environmentally benign and facile synthesis method for a variety of cement paste constituents. In addition, these methods can be used to selectively tune the properties of cement components. The mineral ettringite is an important component of cementitious materials and has additional technological potential due to its ion exchange properties.
Synthesis of ettringite via mechanochemistry is an environmentally friendly alternative to conventional wet-chemical synthesis established in industry. This contribution explores the mechanism of a two-step mechanochemical synthesis of ettringite, which was previously found to greatly improve the reaction conversion as compared with one-pot synthesis. The crystallinity of Al(OH)3 was found to decrease during the first stage of this mechanochemical synthesis. This was correlated to a significant decrease in the particle size of Al(OH)3 in this stage. No other significant changes were found for the other components, suggesting that mechanochemical activation of Al(OH)3 is responsible for the enhanced formation of ettringite by the two-step approach. The environmentally friendly approach developed for ettringite synthesis offers a versatile synthetic strategy, which can be applied to synthesise further cementitious materials.
KW - Ettringite
KW - Mechanochemistry
KW - Sustainability
KW - X-ray diffraction
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-489172
DO - https://doi.org/10.1002/open.201900215
VL - 8
IS - 7
SP - 1012
EP - 1019
PB - ChemPubSoc
AN - OPUS4-48917
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Synthesis of cyclic poly(l-lactide) catalyzed by Bismuth salicylates-A combination of two drugs
N2 - l‐lactide was polymerized in bulk at 160 or 180°C with mixtures of bismuth subsalicylate (BiSub) and salicylic (SA) as catalysts. The SA/Bi ratio and the monomer/Bi ratio were varied. The highest molecular weights (weight average, Mw) were achieved at a SA/Bi ratio of 1/1 (Mw up to 92 000 g mol−1). l‐Lactide was also polymerized with combinations of BiSub and silylated SA, and Mw values up to 120 000 g mol−1 were achieved at 180°C. MALDI‐TOF mass spectrometry and Mark‐Houwink‐Sakurada measurements proved that under optimized reaction conditions the resulting polylactides consist of cycles.
KW - Polylactide
KW - MALDI-TOF MS
KW - Cyclization
KW - Catalyst
KW - Salicylate
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-488622
DO - https://doi.org/10.1002/pola.29473
SN - 0887-624X
SN - 1099-0518
SP - 29473
PB - Wiley
AN - OPUS4-48862
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Michalchuk, Adam
A1 - Trestman, M.
A1 - Rudic, S.
A1 - Portius, P.
A1 - Fincham, P.
A1 - Pulham, C.
A1 - Morrison, C.
T1 - Predicting the reactivity of energetic materials: an ab initio multi-phonon approach
N2 - The ease with which an energetic material (explosives, propellants, and pyrotechnics) can be initiated is a critical parameter to assess their safety and application. Impact sensitivity parameters are traditionally derived experimentally, at great cost and risk to safety. In this work we explore a fully ab initio Approach based on concepts of vibrational energy transfer to predict impact sensitivities for a series of chemically, structurally and energetically diverse molecular materials. The quality of DFT calculations is assessed for a subset of the materials by comparison with experimental inelastic neutron scattering spectra (INS). A variety of models are considered, including both qualitative and quantitative analysis of the vibrational spectra. Excellent agreement against experimental impact sensitivity is achieved by consideration of a multi-phonon ladder-type up-pumping mechanism that includes both overtone and combination pathways, and is improved further by the added consideration of temperature. This fully ab initio approach not only permits ranking of energetic materials in terms of their impact sensitivity but also provides a tool to guide the targeted design of advanced energetic compounds with tailored properties.
KW - Energetic Materials
KW - Prediction
KW - Density Functional Theory
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-489328
DO - https://doi.org/10.1039/c9ta06209b
VL - 7
IS - 33
SP - 19539
EP - 19553
PB - RSC
AN - OPUS4-48932
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Belenguer, A.
A1 - Michalchuk, Adam
A1 - Lampronti, G
A1 - Sanders, J
T1 - Understanding the unexpected effect of frequency on the kinetics of a covalent reaction under ball-milling conditions
N2 - We here explore how ball-mill-grinding frequency affects the kinetics of a disulfide exchange reaction. Our kinetic data show that the reaction progress is similar at all the frequencies studied (15–30 Hz), including a significant induction time before the nucleation and growth process starts. This indicates that to start the reaction an initial energy accumulation is necessary. Other than mixing, the energy supplied by the mechanical treatment has two effects: (i) reducing the crystal size and (ii) creating defects in the structure. The crystal-breaking process is likely to be dominant at first becoming less important later in the process when the energy supplied is stored at the molecular level as local crystal defects. This accumulation is taken here to be the rate-determining step. We suggest that the local defects accumulate preferentially at or near the crystal surface. Since the total area increases exponentially when the crystal size is reduced by the crystal-breaking process, this can further explain the exponential dependence of the onset time on the milling frequency.
KW - Mechanochemistry
KW - Kinetics
KW - Diffraction
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-483361
DO - https://doi.org/10.3762/bjoc.15.120
SN - 2195-951X
VL - 15
SP - 1226
EP - 1235
PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften
CY - Frankfurt, M.
AN - OPUS4-48336
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Feiler, Torvid
A1 - Bhattacharya, Biswajit
A1 - Michalchuk, Adam
A1 - Schröder, V.
A1 - List-Kratochvil, E.
A1 - Emmerling, Franziska
T1 - Mechanochemical Syntheses of Isostructural Luminescent Cocrystals of 9-Anthracenecarboxylic Acid with two Dipyridines Coformers
N2 - Tuning and controlling the solid-state photophysical properties of organic luminophore are very important to develop next-generation organic luminescent materials. With the aim of discovering new functional luminescent materials, new cocrystals of 9-anthracene carboxylic acid (ACA) were prepared with two different dipyridine coformers: 1,2-bis(4-pyridyl)ethylene and 1,2-bis(4-pyridyl)ethane. The cocrystals were successfully obtained by both mechanochemical approaches and conventional solvent crystallization. The newly obtained crystalline solids were characterized thoroughly using a combination of single crystal X-ray diffraction, powder X-ray diffraction, Fourier-transform infrared spectroscopy, differential thermal analysis, and thermogravimetric analysis. Structural analysis revealed that the cocrystals are isostructural, exhibiting two-fold interpenetrated hydrogen bonded networks. While the O–H···N hydrogen bonds adopts a primary role in the stabilization of the cocrystal phases, the C–H···O hydrogen bonding interactions appear to play a significant role in guiding the three-dimensional assembly. Both π···π and C–H···π interactions assist in stabilizing the interpenetrated structure. The photoluminescence properties of both the starting materials and cocrystals were examined in their solid states. All the cocrystals display tunable photophysical properties as compared to pure ACA. Density functional theory simulations suggest that the modified optical properties result from charge transfers between the ACA and coformer molecules in each case. This study demonstrates the potential of crystal engineering to design solid-state luminescence switching materials through cocrystallization.
KW - Cocrystal
KW - Mechanochemical synthesis
KW - Luminescence
KW - X-ray diffraction
KW - DFT calculation
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-518226
DO - https://doi.org/10.3390/cryst10100889
VL - 10
IS - 10
SP - 889
PB - MDPI
AN - OPUS4-51822
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Pellegrino, F.
A1 - Isopescu, R.
A1 - Pellutiè, L.
A1 - Sordello, F.
A1 - Rossi, A. M.
A1 - Ortel, Erik
A1 - Martra, G.
A1 - Hodoroaba, Vasile-Dan
A1 - Maurino, V.
T1 - Machine learning approach for elucidating and predicting the role of synthesis parameters on the shape and size of TiO2 nanoparticles
N2 - In the present work a series of design rules are developed in order to tune the morphology of TiO2 nanoparticles through hydrothermal process. Through a careful experimental design, the influence of relevant process parameters on the synthesis outcome are studied, reaching to the develop predictive models by using Machine Learning methods. The models, after the validation and training, are able to predict with high accuracy the synthesis outcome in terms of nanoparticle size, polydispersity and aspect ratio. Furthermore, they are implemented by reverse engineering approach to do the inverse process, i.e. obtain the optimal synthesis parameters given a specific product characteristic. For the first time, it is presented a synthesis method that allows continuous and precise control of NPs morphology with the possibility to tune the aspect ratio over a large range from 1.4 (perfect truncated bipyramids) to 6 (elongated nanoparticles) and the length from 20 to 140 nm.
KW - Machine learning
KW - Nanoparticles
KW - Titanium dioxide
KW - Size
KW - Shape
KW - Synthesis
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-515084
DO - https://doi.org/10.1038/s41598-020-75967-w
VL - 10
IS - 1
SP - 18910
PB - Springer Nature
AN - OPUS4-51508
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kunkel, B.
A1 - Kabelitz, Anke
A1 - de Oliveira Guilherme Buzanich, Ana
A1 - Wohlrab, S.
T1 - Increasing the Efficiency of Optimized V-SBA-15 Catalysts in the Selective Oxidation of Methane to Formaldehyde by Artificial Neural Network Modelling
N2 - The present study investigates the possibility of improving the selective oxidation of methane to formaldehyde over V-SBA-15 catalysts in two different ways. In a classical approach of catalyst optimization, the in situ synthesis of V-SBA-15 catalysts was optimized with regard to the applied pH value. Among the set of catalysts synthesized, a higher amount of incorporated vanadium, a higher content of polymeric VOx species as well as a less ordered structure of the support material were observed by increasing the pH values from 2.0 to 3.0. An optimum in performance during the selective oxidation of methane to formaldehyde with respect to activity and selectivity was found over V-SBA-15 prepared at a pH value of 2.5. With this knowledge, we have now evaluated the possibilities of reaction control using this catalyst. Specifically, artificial neural network modelling was applied after the collection of 232 training samples for obtaining insight into the influence of different reaction parameters (temperature; gas hourly space velocity (GHSV); and concentration of O2, N2 and H2O) onto methane conversion and selectivity towards formaldehyde.
This optimization of reaction conditions resulted in an outstanding high space-time yield of 13.6 kgCH2O∙kgcat∙h−1
KW - Artificial neural network modelling
KW - Selective oxidation
KW - Molecular VOx catalysts
KW - Formaldehyde
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-517420
DO - https://doi.org/10.3390/catal10121411
VL - 10
IS - 12
SP - 1411
PB - MDPI
AN - OPUS4-51742
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Usmani, Shirin M.
A1 - Plarre, Rüdiger
A1 - Hübert, Thomas
A1 - Kemnitz, E.
ED - Richter, K.
ED - Van de Kulien, J.-W.
T1 - Termite resistance of pine wood treated with nano metal fluorides
N2 - Fluorides are well-known as wood preservatives. One of the limitations of fluoride-based wood preservatives is their high leachability. Alternative to current fluoride salts such as NaF used in wood protection are low water-soluble fluorides. However, impregnation of low water-soluble fluorides into wood poses a challenge. To address this challenge, low water-soluble fluorides like calcium fluoride (CaF2) and magnesium fluoride (MgF2) were synthesized as nanoparticles via the fluorolytic sol−gel synthesis and then impregnated into wood specimens. In this study, the toxicity of nano metal fluorides was assessed by termite mortality, mass loss and visual analysis of treated specimens after eight weeks of exposure to termites, Coptotermes formosanus. Nano metal fluorides with sol concentrations of 0.5 M and higher were found to be effective against termites resulting in 100% termite mortality and significantly inhibited termite feeding. Among the formulations tested, the least damage was found for specimens treated with combinations of CaF2 and MgF2 with an average mass loss less than 1% and visual rating of “1”. These results demonstrate the efficacy of low water-soluble nano metal fluorides to protect wood from termite attack.
KW - Holzschutzmittel
KW - Nanoparticles
KW - Fluorides
KW - Termites
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-514325
DO - https://doi.org/10.1007/s00107-020-01522-z
VL - 78
SP - 493
EP - 499
PB - Springer
CY - Berlin
AN - OPUS4-51432
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - Reply to the comment on “synthesis of cyclic polymers and flaws of the Jacobson-Stockmayer theory” by R. Szymanski
N2 - In a recent publication the authors have presented theoretical and experimental results indicating that the Jacobson–Stockmayer (JS) theory does not provide a correct description of reversible polycondensations for all polymers and for high conversions (e.g. polycondensation in bulk). In this context reversibility means that all condensation step whether resulting in chain growth or in cyclization are reversible and thus, part of an equilibrium. The first two sections of that paper were focused on the demonstration that small, and above all, large cycles can be formed by end-to-end (ete) cyclization in reversible like in irreversible polycondensations. A significant contribution of ete-cyclization to the course of reversible polycondensations was denied by J + S apparently as a contribution to Florýs dogma, that the end groups of long polymer chains will never meet.
KW - Polylactide
KW - MALDI-TOF MS
KW - Jacobsen-Stockmayer theory
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513985
DO - https://doi.org/10.1039/D0PY01118E
VL - 11
IS - 38
SP - 6226
EP - 6228
PB - Royal Society of Chemistry
AN - OPUS4-51398
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Wurzler, Nina
A1 - Schutter, Jan David
A1 - Wagner, R.
A1 - Dimper, Matthias
A1 - Lützenkirchen-Hecht, D.
A1 - Özcan Sandikcioglu, Özlem
T1 - Abundance of Fe(III) during cultivation affects the microbiologically influenced corrosion (MIC) behaviour of iron reducing bacteria Shewanella putrefaciens
N2 - The effect of the presence of Fe(III) during the cultivation on the electrochemical activity and corrosion behaviour of dissimilatory iron reducing bacteria Shewanella putrefaciens was studied by means of ex situ and in situ X-ray absorption near-edge spectroscopy (XANES). Stainless steel AISI 304 and thin iron films were studied as substrates. XANES analysis indicated an accelerated iron dissolution and growth of an oxide/hydroxide film for the culture grown with Fe(III) in comparison to the culture grown in absence of Fe(III). Electrochemical Analysis indicated that the biofilm resulted in acceleration of the general corrosion but provides protection against local corrosion.
KW - Stainless Steel
KW - XANES
KW - Iron
KW - Cyclic Voltammetry
KW - Microbiological Corrosion
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513788
DO - https://doi.org/10.1016/j.corsci.2020.108855
VL - 174
SP - 108855
PB - Elsevier Ltd.
AN - OPUS4-51378
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Chatti, S.
A1 - Kricheldorf, H. R.
T1 - About the transformation of low Tm into high Tm poly(L-lactide)s by annealing under the influence of transesterification catalysts
N2 - Cyclic polylactides were prepared in bulk at 170 °C, crystallized at 120 °C and then annealed at temperatures between 130 and 170 C with variation of catalyst, catalyst concentration and annealing time. The transformation of the initially formed low melting (LTm) crystallites, having melting temperatures (Tm) <180 °C into high melting (HTm) crystallites having Tm values > 189 °C was monitored by means of DSC measurements and characterized in selected cases by SAXS measurements. It was confirmed that the formation of HTm crystallites involves a significant growth of the thickness of the lamellar crystallites along with smoothing of their surface. Annealing at 170 °C for 1 d or longer causes thermal degradation with lowering of the molecular weights, a gradual transition of cyclic into linear chains and a moderate decrease of lamellar thickness. An unexpected result revealed by MALDI TOF mass spectrometry is a partial reorganization of the molecular weight distribution driven by a gain of crystallization enthalpy.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystallization
KW - Annealing
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521062
DO - https://doi.org/10.1039/d0ra10012a
VL - 11
IS - 5
SP - 2872
EP - 2883
PB - Royal Society of Chemistry
AN - OPUS4-52106
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Shipov, A.
A1 - Zaslansky, P.
A1 - Riesemeier, Heinrich
A1 - Segev, G.
A1 - Atkins, A.
A1 - Kalish-Achrai, N.
A1 - Weiner, S.
A1 - Shahar, R.
T1 - The influence of estrogen deficiency on the structural and mechanical properties of rat cortical bone
N2 - Background. Post-menopausal osteoporosis is a common health problem worldwide, most commonly caused by estrogen deficiency. Most of the information regarding the skeletal effects of this disease relates to trabecular bone, while cortical bone is less studied. The purpose of this study was to evaluate the influence of estrogen deficiency on the structure and mechanical properties of cortical bone.
Methods. Eight ovariectomized (OVH) and eight intact (control) Sprague Dawley rats were used. Structural features of femoral cortical bone were studied by light microscopy, scanning electron microscopy and synchrotron-based microcomputer-tomography and their mechanical properties determined by nano-indentation.
Results. Cortical bone of both study groups contains two distinct regions: organized
circumferential lamellae and disordered bone with highly mineralized cartilaginous islands. Lacunar volume was lower in the OVH group both in the lamellar and disorganized regions (182 ± 75 µm3 vs 232 ± 106 µm3 , P < 0.001 and 195 ± 86 µm3 vs. 247 ± 106 µm3 , P < 0.001, respectively). Lacunar density was also lower in both bone regions of the OVH group (40 ± 18 ×103 lacunae/mm3 vs. 47 ± 9×103 lacunae/mm3
in the lamellar region, P = 0.003 and 63 ± 18×103 lacunae/mm3
vs. 75 ± 13×103 lacunae/mm3 in the disorganized region, P < 0.001). Vascular canal volume was lower in the disorganized region of the bone in the OVH group compared to the same Region in the control group (P < 0.001). Indentation moduli were not different between the study groups in both bone regions.
Discussion. Changes to cortical bone associated with estrogen deficiency in rats require high-resolution methods for detection. Caution is required in the application of These results to humans due to major structural differences between human and rat bone.
KW - Estrogen
KW - Disorganized bone
KW - Rat
KW - Lacunae
KW - Ovariectomy
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520798
DO - https://doi.org/10.7717/peerj.10213
VL - 9
SP - e10213
AN - OPUS4-52079
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - ROP of L-lactide and ε-caprolactone catalyzed by tin(ii) and tin(iv) acetates–switching from COOH terminated linear chains to cycles
N2 - The catalytic potential of tin(II)acetate, tin(IV)acetate, dibutyltin-bis-acetate and dioctyl tin-bis-acetate was compared based on polymerizations of L-lactide conducted in bulk at 160 or 130C. With SnAc2 low-Lac/Cat ratios (15/1–50/1) were studied and linear chains having one acetate and one carboxyl end group almost free of cyclics were obtained. Higher monomer/catalyst ratios and lower temperatures favored formation of cycles that reached weight average molecular weights (Mw's) between 100,000 and 2,500,000. SnAc4 yielded mixtures of cycles and linear species under all reaction conditions. Dibutyltin- and dioctyl tin bis-acetate yielded cyclic polylactides under most reaction conditions with Mw's in the range of 20,000–80,000. Ring-opening polymerizations performed with ε-caprolactone showed similar trends, but the formation of COOH-terminated linear chains was significantly more favored compared to analogous experiments with lactide. The reactivity of the acetate catalysts decreased in the following order: SnAc2> SnAc4>Bu2SnAc2 Oct2SnAc2.
KW - Catalyst
KW - MALDI-TOF MS
KW - Ring-opening polymerization
KW - Tin acetates
KW - Polylactide
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520831
DO - https://doi.org/10.1002/pol.20200866
SP - 1
EP - 12
PB - Wiley Online Library
AN - OPUS4-52083
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Frisch, M.
A1 - Laun, J.
A1 - Marquardt, Julien
A1 - Arinchtein, A.
A1 - Bauerfeind, K.
A1 - Bernsmeier, D.
A1 - Bernicke, M.
A1 - Bredow, T.
A1 - Kraehnert, R.
T1 - Bridging experiment and theory: enhancing the electrical conductivities of soft-templated niobium-doped mesoporous titania films†
N2 - Theoretical calculations suggest a strong dependence of electrical conductivity and doping concentration in transition-metal doped titania. Herein, we present a combined theoretical and experimental approach for the prediction of relative phase stability and electrical conductivity in niobium-doped titania as model system.
Our method paves the way towards the development of materials with improved electrical properties.
KW - Electrical conductivity
KW - Prediction relative
KW - Transition-metal doped
KW - System method
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521371
DO - https://doi.org/10.1039/d0cp06544g
SN - 1463-9084
VL - 23
IS - 5
SP - 3219
EP - 3224
PB - Royal Society of Chemistry
AN - OPUS4-52137
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Sentker, K.
A1 - Yildirim, Arda
A1 - Lippmann, M.
A1 - Zantop, A. W.
A1 - Bertram, F.
A1 - Hofmann, T.
A1 - Seeck, O. H.
A1 - Kityk, A.
A1 - Mazza, M. G.
A1 - Schönhals, Andreas
A1 - Huber, P.
T1 - Self-assembly of liquid crystals in nanoporous solids for adaptive photonic metamaterials
N2 - Nanoporous media exhibit structures significantly smaller than the wavelengths of visible light and can thus act as photonic metamaterials. Their optical functionality is not determined by the properties of the base materials, but rather by tailored, multiscale structures, in terms of precise pore shape, geometry, and orientation. Embedding liquid crystals in pore space provides additional opportunities to control light–matter interactions at the single-pore, meta-atomic scale. Here, we present temperature-dependent 3D reciprocal space mapping using synchrotron-based X-ray diffraction in combination with high-Resolution birefringence experiments on disk-like mesogens (HAT6) imbibed in self-ordered arrays of parallel cylindrical pores 17 to 160 nm across in monolithic anodic aluminium oxide (AAO). In agreement with Monte Carlo computer simulations we observe a remarkably rich self-assembly behaviour, unknown from the bulk state. It encompasses transitions between the isotropic liquid state and discotic stacking in linear columns as well as circular concentric ring formation perpendicular and parallel to the pore axis. These textural transitions underpin an optical birefringence functionality, tuneable in magnitude and in sign from positive to negative via pore size, pore surface-grafting and temperature. Our study demonstrates that the advent of large-scale, self-organised nanoporosity in monolithic solids along with confinement-controllable phase behaviour of liquid-crystalline matter at the single-pore scale provides a reliable and accessible tool to design materials with adjustable optical anisotropy, and thus offers versatile pathways to finetune polarisation-dependent light propagation speeds in materials. Such a tailorability is at the core of the emerging field of transformative optics, allowing, e.g., adjustable light absorbers and extremely thin metalenses.
KW - Discotic Liquid Crystals
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-499601
DO - https://doi.org/10.1039/c9nr07143a
SP - 1
EP - 14
PB - RSC Royal Society of Chemistry
AN - OPUS4-49960
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Meyer, A.
A1 - Weidner, Steffen
A1 - Kricheldorf, H.
T1 - Stereocomplexation of cyclic polylactides with each other and with linear poly(L-lactide)s
N2 - Two kinds of cyclic poly(D- and L-lactide)s were synthesized, namely CI labeled samples mainly consisting of even-numbered cycles with low dispersity and CII, CIII or CIV-labeled ones consisting of equal amounts of even and odd-numbered cycles with high dispersity and igher molecular weights (Mw up to 300 000). Furthermore, linear poly L-lactide)s were prepared by initiation with ethanol and in both series the molecular weight was varied. The formation of stereocomplexes from cyclic poly(D-lactide)s and all kinds of poly L-lactide)s was performed in dichloromethane/toluene mixtures. The stereocomplexes crystallized from the reaction mixture were characterized in the virgin state and after annealing at 205 °C.
Stereocomplexes free of stereohomopolymers with crystallinities up to 80% were obtained from all experiments in yields ranging from 60 to 80%. Despite the high annealing temperature (maintained for 1 h), little transesterification was observed and the crystallinity slightly increased.
KW - Polylactide
KW - MALDI-TOF MS
KW - Stereocomplex
KW - Cyclic
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-496693
DO - https://doi.org/10.1039/c9py01236b
VL - 10
SP - 6191
EP - 6199
PB - Royal Society for Chemistry
AN - OPUS4-49669
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Henning, L. M.
A1 - Simon, U.
A1 - Gurlo, A.
A1 - Smales, Glen Jacob
A1 - Bekheet, M. F.
T1 - Grafting and stabilization of ordered mesoporous silica COK-12 with graphene oxide for enhanced removal of methylene blue
N2 - Large-pore ordered mesoporous silica (OMS) COK-12, analogous to the well-known SBA-15, but synthesized in a more environmentally friendly way and exhibiting a shorter plate-like structure, was grafted with different amounts of graphene oxide (GO) for the first time in an inexpensive and rapid process, that was successfully upscaled. Samples were examined with nitrogen sorption analysis, SAXS, Raman spectroscopy, XPS, and zeta potential analysis. Adsorption experiments with the cationic dye methylene blue (MB) were conducted on the grafted materials and on pure COK-12, taking into account the influence of initial dye concentration (30–600 mg L-1), adsorbent dosage (0.2–14 g L-1), contact time (0.3–300 min), solution pH (4 10), and influence of salts and temperature (0–1 M NaCl, 80 C) to simulate industrial dye effluent. The adsorption process was found to be represented best by the Langmuir isotherm model, i.e., adsorption is a monolayer process. The calculated maximum Adsorption capacities were found to be 20.2 and 197.5 mg g-1 at dosages of 5 and 0.5 g L-1 for pure COK-12 and COK-12 grafted with 50 wt% GO, respectively, at pH 5.65 and MB concentration of 100 mg L-1.
Adsorption kinetics were found to follow the pseudo-second order model, i.e., chemisorption is the rate controlling step. The adsorption performances could be well preserved at simulated dye effluent.
Desorption was found to be most effective with hydrochloric acid. The COK-12 grafted with GO presented in this work shows superior adsorption properties in comparison to other grafted OMS materials. In addition, grafting with GO remarkably improved the stability of COK-12 in aqueous solution.
KW - COK-12
KW - Mesoporous Silica
KW - Graphene Oxide
KW - Large-pore
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-497788
UR - https://pubs.rsc.org/en/content/articlehtml/2019/ra/c9ra05541j
DO - https://doi.org/10.1039/c9ra05541j
VL - 9
IS - 62
SP - 36271
EP - 36284
PB - Royal Society of Chemistry
AN - OPUS4-49778
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Kricheldorf, H. R.
A1 - Scheliga, F.
T1 - Ring-expansion copolymerization of L-lactide and glycolide
N2 - 1:1 Copolymerizations of glycolide (GL) and L-lactide (LA) is performed in bulk at 100°C and at 160°C with four cyclic tin catalysts. The resulting copolyesters are characterized by SEC measurements, 1H and 13C NMR spectroscopy and by MALDI TOF mass spectrometry. At 160°C and longer reaction time (22 h) nearly complete conversion of both monomers is achieved, and cyclic copolymers with nearly random sequences are formed. At shorter times (0.5-3.0 h, depending on catalyst) the conversion of LA is incomplete, and only cyclics having even numbers of lactyl units are obtained. At 100°C at 22 h again cycles mainly consisting of even numbered lactyl units are formed, but with even and odd numbers of glycolyl units. Copolymerization of lactide at 160°C with small amounts of GL show that formation of high Tm crystallites (Tm > 190°C) is hindered even when only > 2% of GL is added. For polyglycolide containing a smaller amount of lactide complete solubility in hexafluoroisopropanol is only observed around and above 20 mol% of lactide.
KW - Ring-expansion polymerization
KW - Copolymerization
KW - MALDI-TOF MS
KW - L-lactide
KW - Glycolide
KW - Crystallization
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520270
DO - https://doi.org/10.1002/macp.202000307
SN - 1022-1352
VL - 22
IS - 3
SP - 307
PB - WileyVCH
AN - OPUS4-52027
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - High molecular weight poly(l-lactide) via ring-opening polymerization with bismuth subsalicylate-The role of cocatalysts
N2 - The catalytic potential of bismuth subsalicylate (BiSub), a commercial drug, for ring-opening polymerization (ROP) of L-lactide was explored by variation of co-catalyst and polymerization time. Various monofunctional phenols or carboxylic acids, aromatic ortho-hydroxy acids and diphenols were examined as potential co-catalysts. 2,2´-Dihydroxybiphenyl proved to be the most successful co-catalyst yielding weight average molecular weights (uncorrected Mw values up to 185 000) after optimization of reaction time and temperature. Prolonged heating (>1-2h) depending on catalyst concentration) caused thermal degradation. In polymerization experiments with various commercial Bi(III) salts a better alternative to BiSub was not found. By means of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry a couple of unusual and unexpected transesterification reactions were discovered. Finally, the effectiveness of several antioxidants and potential catalyst poisons was explored, and triphenylphosphine was found to be an effective catalyst poison.
KW - Polylactide
KW - MALDI-TOF MS
KW - Ring-opening polymerization
KW - Bismuth
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-519513
DO - https://doi.org/10.1002/app.50394
SN - 0021-8995
VL - 138
IS - 19
SP - 50394
PB - Wiley
AN - OPUS4-51951
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Chewle, Surahit
A1 - Emmerling, Franziska
A1 - Weber, M.
T1 - Effect of choice of solvent on crystallization pathway of paracetamol: An experimental and theoretical case study
N2 - The choice of solvents influences crystalline solid formed during the crystallization of active pharmaceutical ingredients (API). The underlying effects are not always well understood because of the complexity of the systems. Theoretical models are often insufficient to describe this phenomenon. In this study, the crystallization behavior of the model drug paracetamol in different solvents was studied based on experimental and molecular dynamics data. The crystallization process was followed in situ using time-resolved Raman spectroscopy. Molecular dynamics with simulated annealing algorithm was used for an atomistic understanding of the underlying processes. The experimental and theoretical data indicate that paracetamol molecules adopt a particular geometry in a given solvent predefining the crystallization of certain polymorphs
KW - Crystallization
KW - Nucleation
KW - Polymorphism
KW - Raman spectroscopy
KW - Cassical nucleation theory
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520052
DO - https://doi.org/10.3390/cryst10121107
SN - 2073-4352
VL - 10
IS - 12
SP - 1
EP - 10
PB - MDPI
CY - Basel
AN - OPUS4-52005
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - High Tm linear poly(L-lactide)s prepared via alcohol-initiated ROPs of L-lactide
N2 - Alcohol-initiated ROPs of L-lactide were performed in bulk at 160 °C for 72 h with variation of the catalyst or with variation of the initiator (aliphatic alcohols). Spontaneous crystallization was only observed when cyclic Sn(II) compounds were used as a catalyst. Regardless of initiator, high melting crystallites with melting temperatures (Tm) of 189–193 °C were obtained in almost all experiments with Sn(II) 2,2′-dioxybiphenyl (SnBiph) as catalyst, even when the time was shortened to 24 h. These HTm poly(lactide)s represent the thermodynamically most stable form of poly(L-lactide). Regardless of the reaction conditions, such high melting crystallites were never obtained when Sn(II) 2-ethylhexanoate (SnOct2) was used as catalyst. SAXS measurements evidenced that formation of HTm poly(L-lactide) involves growth of the crystallite thickness, but chemical modification of the crystallite surface (smoothing) seems to be of greater importance. A hypothesis, why the “surface smoothing” is more effective for crystallites of linear chains than for crystallites composed of cycles is discussed.
KW - Polylactide
KW - MALDI-TOF MS
KW - Ring-opening polymerization
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-524330
DO - https://doi.org/10.1039/d1ra01990b
VL - 11
IS - 23
SP - 14093
EP - 14102
PB - Royal Society of Chemistry
AN - OPUS4-52433
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Weidner, Steffen
T1 - ROP of L-lactide and ε-caprolactone catalyzed by tin(ii) andtin(iv) acetates–switching from COOH terminated linear chains to cycles
N2 - The catalytic potential of tin(II)acetate, tin(IV)acetate, dibutyltin-bis-acetate and dioctyl tin-bis-acetate was compared based on polymerizations of L-lactide conducted in bulk at 160 or 130°C. With SnAc2 low-Lac/Cat ratios (15/1–50/1) were studied and linear chains having one acetate and one carboxyl end group almost free of cyclics were obtained. Higher monomer/catalyst ratios and lower temperatures favored formation of cycles that reached weight average molecular weights (Mw's) between 100,000 and 2,500,000. SnAc4 yielded mixtures of cycles and linear species under all reaction conditions. Dibutyltin- and dioctyl tin bis-acetate yielded cyclic polylactides under most reaction conditions with Mw's in the range of 20,000–80,000. Ring-opening polymerizations performed with ε-caprolactone showed similar trends, but the formation of COOH-terminated linear chains was significantly more favored compared to analogous experiments with lactide. The reactivity of the acetate catalysts decreased in the following order: SnAc2> SnAc4>Bu2SnAc2~Oct2SnAc2
KW - Polylactide
KW - MALDI-TOF MS
KW - Catalyst
KW - Ring-opening polymerization
KW - Tin acetates
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521923
DO - https://doi.org/10.1002/pol.20200866
VL - 59
IS - 5
SP - 439
EP - 450
PB - Wiley Online Library
AN - OPUS4-52192
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Michalchuk, Adam
A1 - Boldyreva, E.
A1 - Belenguer, A. M.
A1 - Emmerling, Franziska
A1 - Boldyrev, V. V.
T1 - Tribochemistry, mechanical alloying, mechanochemistry: what is in a name?
N2 - Over the decades, the application of mechanical force to influence chemical reactions has been called by various names: mechanochemistry, tribochemistry, mechanical alloying, to name but a few. The evolution of these terms has largely mirrored the understanding of the field. But what is meant by these terms, why have they evolved, and does it really matter how a process is called? Which parameters should be defined to describe unambiguously the experimental conditions such that others can reproduce the results, or to allow a meaningful comparison between processes explored under different conditions? Can the information on the process be encoded in a clear, concise, and self-explanatory way? We address these questions in this Opinion contribution, which we hope will spark timely and constructive discussion across the international mechanochemistry community.
KW - Mechanochemistry
KW - Tribochemistry
KW - Mechanical alloying
KW - Tribology
KW - Mechanical activation
KW - Nomenclature
KW - Mechanochemical pictographs
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-523291
DO - https://doi.org/10.3389/fchem.2021.685789
SN - 2296-2646
VL - 9
SP - 1
EP - 29
PB - Frontiers Media
CY - Lausanne
AN - OPUS4-52329
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zänker, Steffen
A1 - Scholz, G.
A1 - Xu, W.
A1 - Kemnitz, E.
A1 - Emmerling, Franziska
T1 - Structure and properties of fluorinated and non-fluorinated Ba-coordination polymers - the position of fluorine makes the difference
N2 - As the most electronegative element, fluorine has a strong influence on material properties such as absorption behaviour or chemical and thermal stability. Fluorine can be easily integrated into coordination polymers (CPs) via a fluorinated acetate, here trifluoroacetate in Ba(CF3COO)2, or directly via a metal fluorine bond (BaF(CH3COO)). In the present study both possibilities of fluorine integration were tested and their effect on structure and properties of barium coordination polymers was investigated in comparison with the non-fluorinated barium acetate (Ba(CH3COO)2). In addition to the study of their thermal behaviour and their decomposition temperature, the CPs structures were tested for their application as possible anode materials in lithium ion batteries and for their sorption of water and ammonia. The properties of the CPs can be traced back to the individual structural motifs and could thus trigger new design ideas for CPs in LIBs and/or catalysis.
KW - Alkaline earth metal coordination polymers
KW - Lithium-ion battery
KW - Water stability
KW - Fluorine coordination
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-524041
DO - https://doi.org/10.1002/zaac.202000360
SN - 0044-2313
VL - 647
IS - 9
SP - 1014
EP - 1024
PB - Wiley-VCH GmbH
AN - OPUS4-52404
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Zosef, M.
A1 - Fahmy, Alaa
A1 - El Hotaby, W.
A1 - Hassan, A.
A1 - Khalil, A.
A1 - Anis, B.
T1 - High performance graphene-based PVF foam for lead removal from water
N2 - The synthesis and optimization of superior and eco-friendly sorbents for Pb(II) pose a great challenge in the field of water treatment. The sorbent was developed by introducing graphene oxide (GO) into the matrix of polyvinyl formaldehyde (PVF) foam. The immobilization of GO in PVF results in significant increase in the maximum adsorption capacity (Qt) of GO powder for Pb(II), from ≈800 to ≈1730 mg g−1 in the case of GO/PVF foam. As compared with GO powder in Pb(II) aqueous solutions, PVF matrix keeps GO sheets stable without any agglomeration. The large surface area of GO sheet allows the abundant oxygenated functional groups on its surface to participate effectively in the Pb(II) adsorption process, leading to the huge increase of the Qt. Adsorption isotherms and kinetic studies indicated that the sorption process of Pb(II) on GO/PVF was done on heterogenous surface by ion-exchange reaction. The GO/PVF foam showed an excellent reusability for more than 10 cycles with almost the same efficiency and without any significant change in its physical properties.
KW - Water treatment
KW - Graphene oxide
KW - Lead ions
KW - Polyvinyl formaldehyde foam
KW - Superior sorbent
PY - 2020
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-523013
DO - https://doi.org/10.1016/j.jmrt.2020.08.011
VL - 9
IS - 5
SP - 11861
EP - 11875
PB - Elsevier B.V.
AN - OPUS4-52301
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H. R.
A1 - Scheliga, F.
A1 - Weidner, Steffen
T1 - What does conversion mean in polymer science?
N2 - The definition of the term “conversion” is discussed for a variety of polymer syntheses. It is demonstrated that in contrast to organic and inorganic chemistry several different definitions are needed in polymer science. The influence of increasing conversion on structure and topology of homo- and Copolymers is illustrated. Chain-growth polymerizations, such as radical polymerization or living anionic polymerizations of vinyl monomers, condensative chain polymerization, two and three-dimensional step-growth polymerizations, ring–ring or chain–chain equilibration and chemical modification of polymers are considered.
KW - Polymers
KW - Polymerization
KW - Conversion
KW - Polycondensation
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-523597
DO - https://doi.org/10.1002/macp.202100010
VL - 222
IS - 8
SP - 10
PB - Wiley VCH
AN - OPUS4-52359
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Akbar, S.
A1 - Hasanain, S.K.
A1 - Ivashenko, O.
A1 - Dutka, M.V.
A1 - Akhtar, N.
A1 - De Hosson, J.Th.M.
A1 - Ali, Naveed
A1 - Rudolf, P.
T1 - Defect ferromagnetism in SnO2:Zn2+ hierarchical nanostructures: correlation between structural, electronic and magnetic properties
N2 - We report on the ferromagnetism of Sn1-xZnxO2 (x < 0.1) hierarchical nanostructures with various morphologies synthesized by a solvothermal route. A room temperature ferromagnetic and paramagnetic response was observed for all compositions, with a maximum in ferromagnetism for x = 0.04. The ferromagnetic behaviour was found to correlate with the presence of zinc on substitutional Sn sites and with a low oxygen vacancy concentration in the samples. The morphology of the nanostructures varied with zinc concentration. The strongest ferromagnetic response was observed in nanostructures with well-formed shapes, having nanoneedles on their surfaces. These nanoneedles consist of (110) and (101) planes, which are understood to be important in stabilizing the ferromagnetic defects. At higher zinc concentration the nanostructures become eroded and agglomerated, a phenomenon accompanied with a strong decrease in their ferromagnetic response. The observed trends are explained in the light of recent computational studies that discuss the relative stability of ferromagnetic defects on various surfaces and the role of oxygen vacancies in degrading ferromagnetism via an increase in free electron concentration.
KW - Ferromagnetism
KW - Nanostructures
KW - Magnetic properties
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-473014
DO - https://doi.org/10.1039/c9ra00455f
SN - 2046-2069
VL - 9
IS - 7
SP - 4082
EP - 4091
PB - Royal Society of Chemistry
AN - OPUS4-47301
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gaillard, C.
A1 - Mech, A.
A1 - Wohlleben, W.
A1 - Babick, F.
A1 - Hodoroaba, Vasile-Dan
A1 - Ghanem, A.
A1 - Weigel, S.
A1 - Rauscher, H.
T1 - A technique-driven materials categorisation scheme to support regulatory identification of nanomaterials
N2 - Worldwide there is a variety of regulatory provisions addressing nanomaterials. The identification as nanomaterial in a regulatory context often has the consequence that specific legal rules apply. In identifying nanomaterials, and to find out whether nanomaterial-specific provisions apply, the external size of particles is globally used as a criterion. For legal certainty, its assessment for regulatory purposes should be based on measurements and methods that are robust, fit for the purpose and ready to be accepted by different stakeholders and authorities. This should help to assure the safety of nanomaterials and at the same time facilitate their international trading. Therefore, we propose a categorisation scheme which is driven by the capabilities of common characterisation techniques for particle size measurement. Categorising materials according to this scheme takes into account the particle properties that are most important for a determination of their size. The categorisation is exemplified for the specific particle number based size metric of the European Commission's recommendation on the definition of nanomaterial, but it is applicable to other metrics as well. Matching the performance profiles of the measurement techniques with the material property profiles (i) allows selecting the most appropriate size determination technique for every type of material considered, (ii) enables proper identification of nanomaterials, and (iii) has the potential to be accepted by regulators, industry and consumers alike. Having such a scheme in place would facilitate the regulatory assessment of nanomaterials in regional legislation as well as in international relations between different regulatory regions assuring the safe trade of nanomaterials.
KW - Nanomaterial
KW - Nanoparticles
KW - Categorisation scheme
KW - EC definition of a nanomaterial
KW - Regulatory identification of nanomaterials
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-471623
DO - https://doi.org/10.1039/C8NA00175H
SN - 2516-0230
SP - 1
EP - 11
PB - The Royal Society of Chemistry
AN - OPUS4-47162
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Domonov, D.P.
A1 - Pechenyuk, S.I.
A1 - Semushina, Y.P.
A1 - Yusenko, Kirill
T1 - Solid state transformation in inner coordination sphere of [Co(NH3)6][Fe(C2O4)3]·3H2O as a route to access catalytically active Co-Fe materials
N2 - Thermal decomposition of [Co(NH₃)₆][Fe(C₂O₄)₃]∙3H₂O in argon atmosphere, at a low heating rate (3°/min), and in large amounts of the initial complex (~0.1 mole), has been studied. It was possible to distinguish four decomposition steps upon heating: In the temperature range of 50⁻100 °C-the loss of crystal water; 100⁻190 °C-stability region of dehydrated complex; 230⁻270 °C-the range of stability of intermediate phase with the formula CoFe(NH₃)₂(C₂O₄)₂; 270⁻350 °C-thermal decomposition of the intermediate with the formation of metallic products and further air oxidation with the formation of Co1.5Fe1.5O₄. Catalytic properties of thermolysis products were tested in the decomposition reaction of H₂O₂ (inactive), oxidation of acetone (average activity), and decomposition of ammonium perchlorate (highly active).
KW - Double complex salts
KW - Catalysts
KW - Single-source precursors
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-474014
DO - https://doi.org/10.3390/ma12020221
SN - 1996-1944
VL - 12
IS - 2
SP - 221, 1
EP - 10
PB - mdpi
CY - Zürich
AN - OPUS4-47401
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Santos de Freitas, M.
A1 - Araghi, R. R.
A1 - Brandenburg, E.
A1 - Leiterer, Jork
A1 - Emmerling, Franziska
A1 - Folmert, K.
A1 - Gerling-Driessen, U. I. M.
A1 - Bardiaux, B.
A1 - Böttcher, C.
A1 - Pagel, K.
A1 - Diehl, A.
A1 - v. Berlepsch, H.
A1 - Oschkinat, H.
A1 - Koksch, B.
T1 - The protofilament architecture of a de novo designed coiled coil-based amyloidogenic peptide
N2 - Amyloid fibrils are polymers formed by proteins under specific conditions and in many cases they are related to pathogenesis, such as Parkinson’s and Alzheimer’s diseases. Their hallmark is the presence of a β-sheet structure. High resolution structural data on these systems as well as information gathered from multiple complementary analytical techniques is needed, from both a fundamental and a pharmaceutical perspective. Here, a previously reported de novo designed, pH-switchable coiled coil-based peptide that undergoes structural transitions resulting in fibril formation under physiological conditions has been exhaustively characterized by transmission electron microscopy (TEM), cryo-TEM, atomic force microscopy (AFM), wide-angle X-ray scattering (WAXS) and solid-state NMR (ssNMR). Overall, a unique 2-dimensional carpet-like assembly composed of large coexisiting ribbon-like, tubular and funnel-like structures with a clearly resolved protofilament substructure is observed. Whereas electron microscopy and scattering data point somewhat more to a hairpin model of β-fibrils, ssNMR data obtained from samples with selectively labelled peptides are in agreement with both, hairpin structures and linear arrangements.
KW - Amyloid
KW - Elektronenmikroskopie
PY - 2018
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-458713
UR - https://www.sciencedirect.com/science/article/pii/S1047847718301333
DO - https://doi.org/10.1016/j.jsb.2018.05.009
SN - 1047-8477
VL - 203
IS - 3
SP - 263
EP - 272
PB - Elsevier
AN - OPUS4-45871
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Diehn, Sabrina
A1 - Zimmermann, B.
A1 - Bagcioglu, M.
A1 - Seifert, Stephan
A1 - Kohler, A.
A1 - Ohlson, M.
A1 - Fjellheim, S.
A1 - Weidner, Steffen
A1 - Kneipp, Janina
T1 - Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) shows adaption of grass pollen composition
N2 - MALDI time-of-flight mass spectrometry (MALDI-TOF MS) has become a widely used tool for the classification of biological samples. The complex chemical composition of pollen grains leads to highly specific, fingerprint-like mass spectra, with respect to the pollen species. Beyond the species-specific composition, the variances in pollen chemistry can be hierarchically structured, including the level of different populations, of environmental conditions or different genotypes. We demonstrate here the sensitivity of MALDI-TOF MS regarding the adaption of the chemical composition of three Poaceae (grass) pollen for different populations of parent plants by analyzing the mass spectra with partial least squares discriminant analysis (PLS-DA) and principal component analysis (PCA). Thereby, variances in species, population and specific growth conditions of the plants were observed simultaneously. In particular, the chemical pattern revealed by the MALDI spectra enabled discrimination of the different populations of one species. Specifically, the role of environmental changes and their effect on the pollen chemistry of three different grass species is discussed. Analysis of the Group formation within the respective populations showed a varying influence of plant genotype on the classification, depending on the species, and permits conclusions regarding the respective rigidity or plasticity towards environmental changes.
KW - Pollen
KW - MALDI-TOF MS
KW - Classification
KW - Partial least square discriminant analysis (PLS-DA)
KW - Principal component analysis (PCA)
PY - 2018
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-465294
DO - https://doi.org/10.1038/s41598-018-34800-1
SN - 2045-2322
VL - 8
IS - 1
SP - 16591, 1
EP - 11
PB - Nature
AN - OPUS4-46529
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Greiser, Sebastian
A1 - Gluth, Gregor
A1 - Sturm, Patrick
A1 - Jäger, Christian
T1 - 29Si{27Al}, 27Al{29Si} and 27Al{1H} double-resonance NMR spectroscopy study of cementitious sodium aluminosilicate gels (geopolymers) and gel-zeolite composites
N2 - The influence of starting materials and synthesis route on the properties and the structure of cementitious sodium aluminosilicate gels is not fully understood, partly due their amorphous nature and the fact that they often contain residual reactants, which can make the results of single-pulse NMR spectroscopy applied to these materials difficult to interpret or ambiguous. To overcome some of these limitations, 29Si{27Al} TRAPDOR NMR as well as 27Al{29Si} and 27Al{1H} REDOR NMR spectroscopy were applied to materials synthesized by the one-part alkali-activation route from three different amorphous silica starting materials, including rice husk ash. The latter led to formation of a fully amorphous sodium aluminosilicate gel (geopolymer), while the materials produced from the other silicas contained amorphous phase and crystalline zeolites. Application of the double-resonance NMR methods allowed to identify hydrous alumina gel domains in the rice husk ash-based material as well as significantly differing amounts of residual silica in the three cured materials. Four-coordinated Al existed not only in the aluminosilicate gel framework but also in a water-rich chemical environment with only a small amount of Si in proximity, likely in the alumina gel or possibly present as extra-framework Al in the aluminosilicate gel. The results demonstrate how the employment of different silica starting materials determines the phase assemblage of one-part alkali-activated materials, which in turn influences their engineering properties such as the resistance against chemically/biologically aggressive media.
KW - Alkali-activated materials
KW - Solid-state NMR
KW - Aluminium hydroxide
KW - Rice husk ash
PY - 2018
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-469353
DO - https://doi.org/10.1039/C8RA09246J
SN - 2046-2069
VL - 8
IS - 70
SP - 40164
EP - 40171
PB - Royal Society of Chemistry
AN - OPUS4-46935
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gramse, G.
A1 - Schönhals, Andreas
A1 - Kienberger, F.
T1 - Nanoscale dipole dynamics of protein membranes studied by broadband dielectric microscopy
N2 - We investigate the nearfield dipole mobility of protein membranes in a wide frequency range from 3 kHz to 10 GHz. The results of our nanoscale dielectric images and spectra of bacteriorhodopsin (bR) reveal Debye relaxations with time constants of τ ∼ 2 ns and τ ∼ 100 ns being characteristic of the Dipole moments of the bR retinal and α-helices, respectively. However, the dipole mobility and therefore the protein biophysical function depend critically on the amount of surface water surrounding the protein, and the characteristic mobility in the secondary structure is only observed for humidity levels <30%. Our results have been achieved by adding the frequency as a second fundamental dimension to quantitative dielectric microscopy. The key elements for the success of this advanced technique are the employed heterodyne detection scheme, the broadband electrical signal source, a high frequency optimized cabling, development of calibration procedures and precise finite element modelling. Our study demonstrates the exciting possibilities of broadband dielectric microscopy for the investigation of dynamic processes in cell bioelectricity at the individual molecular level. Furthermore, the technique may shed light on local dynamic processes in related materials science applications like semiconductor Research or nano-electronics.
KW - Broadband dielectric microscopy
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-475230
DO - https://doi.org/10.1039/c8nr05880f
SN - 2040-3372
VL - 11
IS - 10
SP - 4303
EP - 4309
PB - RSC
AN - OPUS4-47523
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hampel, Marco
A1 - Schenderlein, Matthias
A1 - Schary, Christian
A1 - Dimper, Matthias
A1 - Özcan Sandikcioglu, Özlem
T1 - Efficient detection of localized corrosion processes on stainless steel by means of scanning electrochemical microscopy (SECM) using a multi-electrode approach
N2 - High resolution analysis of corrosion processes on stainless steels is a challenging task. The application of local electrochemical techniques such as scanning electrochemical microscopy (SECM) has opened new possibilities for the detection of corrosion products and activity on metallic surfaces. However, due to its stochastic nature, the analysis of pitting corrosion requires being at the right place at the right time. Scanning over large areas at a high resolution not only leads to long scan durations but also leaves many short-lived processes undetected. In this paper we present the combined automated operation of SECM and wire multi-electrodes connected to a multi-electrode analyzer (MMA). The inter-electrode currents between 25 wire electrodes connected via zero resistance ammeters (ZRA) are measured by the MMA at open circuit potential (OCP) and the electrodes reporting anodic currents are detected automatically to be analyzed by means of SECM. The results demonstrate the successful application of this methodology for the detection of unstable and stable pitting processes on 304 stainless steel in a corrosive aqueous environment.
KW - Scanning electrochemical microscope (SECM)
KW - Localised corrosion
KW - Corrosion monitoring
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-478646
DO - https://doi.org/10.1016/j.elecom.2019.02.019
VL - 101
SP - 52
EP - 55
PB - Elsevier B.V.
AN - OPUS4-47864
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Stroh, Julia
A1 - Ali, Naveed Zafar
A1 - Maierhofer, Christiane
A1 - Emmerling, Franziska
T1 - Ettringite via Mechanochemistry: A Green and Rapid Approach for Industrial Application
N2 - Here, we report on a first mechanochemical synthesis of ettringite, an important cement hydrate phase. The mineral compound ettringite ([Ca3Al(OH)6]2·(SO4)3·26H2O) occurs rarely in nature, but is common for cement-based materials. Ettringite has wide technical application in the ceramic and paper industry. However, its typical wet-chemical synthesis is cumbersome and produces waste water and CO2 emissions. Here, we investigate the first mechanochemical synthesis of ettringite for developing an easy and sustainable alternative for industrial application. The mechanosynthesis was monitored in situ by coupled synchrotron X-ray diffraction (XRD) and infrared thermography (IRT). The consumption of the reactants and the formation of the reaction product were monitored with time-resolved XRD. IRT showed the temperature increase based on the exothermic reaction. The reaction conversion was significantly improved changing the strategy of the mechanosynthesis from a one- to a two-step process. The latter included neat pregrinding of solid reactants followed by a delayed addition of the stoichiometric amount of water. Thus, an increase of reaction conversion from 34 to 94% of ettringite could be achieved.
KW - XRD
KW - Mechanochemistry
KW - Ettringite
KW - In situ
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-479016
DO - https://doi.org/10.1021/acsomega.9b00560
SN - 2470-1343
VL - 4
IS - 4
SP - 7734
EP - 7737
PB - ACS Publications
CY - Washington, DC
AN - OPUS4-47901
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - Syntheses of Polyglycolide via Polycondensation: A Reinvestigation
N2 - The Na salt of chloroacetic acid is condensed in suspension. Furthermore,glycolic acid is condensed in bulk or in concentrated solution by means of SnCl2 or 4-toluene sulfonic acid (TSA) as catalysts. The temperatures are varied from 160 to 200°C and the time from 1 to 5 days. Low molar mass cyclic poly(glycolic acid) (PGA) is detected by means of matrix-assisted laser desorption ionization time-of-flight (MALDI TOF) mass spectrometry in most PGAs. A predominance of certain cycles having an even number of repeat units is observed suggesting a thermodynamically favored formation of extended-ring crystals. Extremely high melting temperatures (up to 237.5°C)and high melting enthalpies are found for polycondensations with TSA in 1,2-dichlorobenzene.
KW - MALDI TOF MS
KW - Polycondensation
KW - Polyglycolide
KW - Cyclization
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-596856
DO - https://doi.org/10.1002/macp.202300397
IS - 2300397
SP - 1
EP - 7
PB - Wiley VHC-Verlag
AN - OPUS4-59685
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weidner, Steffen
A1 - Meyer, A.
A1 - Kricheldorf, H.
T1 - Cyclic polyglycolides via ring-expansion polymerization with cyclic tin catalysts
N2 - Glycolide was polymerized in bulk with two cyclic catalysts − 2,2-dibutyl-2-stanna-1,3-dithiolane (DSTL) and 2-stanna-1,3-dioxa-4,5,6,7-dibenzepane (SnBiph). The monomer/initiator ratio, temperature (140 – 180 °C) and time (1–––4 days) were varied. The MALDI TOF mass spectra exclusively displayed peaks of cyclic polyglycolide (PGA) and revealed an unusual “saw-tooth pattern” in the mass range below m/z 2 500 suggesting formation of extended ring crystallites. The DSC measurements indicated increasing crystallinity with higher temperature and longer time, and after annealing for 4 d at 160 °C a hitherto unknown and unexpected glass transition was found in the temperature range of 170–185 °C. Linear PGAs prepared by means of metal alkoxides under identical conditions did not show the afore-mentioned features of the cyclic PGAs, neither in the mass spectra nor in the DSC measurements. All PGAs were also characterized by SAXS measurements, which revealed relatively small L-values suggesting formation of thin crystallites in all cases with little influence of the reaction conditions.
KW - Polyglycolide
KW - MALDI-TOF MS
KW - Ring-expansion polymerization
KW - Crystals
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-595541
DO - https://doi.org/10.1016/j.eurpolymj.2024.112811
SN - 0014-3057
VL - 207
SP - 1
EP - 9
PB - Elsevier Ltd.
AN - OPUS4-59554
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Manzoni, Anna Maria
A1 - Dubois, F.
A1 - Mousa, M. S.
A1 - von Schlippenbach, C.
A1 - Többens, D. M.
A1 - Yesilcicek, Yasemin
A1 - Zaiser, E.
A1 - Hesse, René
A1 - Haas, S.
A1 - Glatzel, U.
T1 - On the Formation of Eutectics in Variations of the Al10Co25Cr8Fe15Ni36Ti6 Compositionally Complex Alloy
N2 - Superalloy inspired Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy is known for its gamma-gamma' microstructure and the third Heusler phase. Variations of this alloy, gained by replacing 0.5 or 1 at. pct Al by the equivalent amount of Mo, W, Zr, Hf or B, can show more phases in addition to this three-phase morphology. When the homogenization temperature is chosen too high, a eutectic phase formation can take place at the grain boundaries, depending on the trace elements: Mo and W do not form eutectics while Hf, Zr and B do. In order to avoid the eutectic formation and the potential implied grain boundary weakening, the homogenization temperature must be chosen carefully by differential scanning calorimetry measurements. A too low homogenization temperature, however, could impede the misorientation alignment of the dendrites in the grain. The influence of grain boundary phases and incomplete dendrite re-orientation are compared and discussed.
KW - High entropy alloy
KW - Eutectic
KW - Homogenization
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543504
DO - https://doi.org/10.1007/s11661-020-06091-7
VL - 52
IS - 1
SP - 143
EP - 150
PB - Springer
AN - OPUS4-54350
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
A1 - Meyer, A.
T1 - Syntheses of high molecular mass polyglycolides via ring-opening polymerization with simultaneous polycondensation(ROPPOC) by means of tin and zinc catalysts
N2 - Glycolide was polymerized in bulk by means of four different ROPPOC catalysts: tin(II) 2-ethylhexanoate (SnOct2), dibutyltin bis(pentafluoro-phenoxide) (BuSnOPF),zinc biscaproate (ZnCap), and zinc bis(pentafluoro-phenyl sulfide) (ZnSPF). The temperature was varied between 110 and 180°C and the time between 3 h and 7 days. For the few polyglycolides (PGAs) that were soluble extremely high molecular masses were obtained. The MALDI TOF mass spectra had all a low signal-to-noise ration and displayed the peaks of cyclic PGAs with a“saw-tooth pattern ”indicating formation of extended-ring crystallites in the mass range below m/z 2500. The shape of DSC curves varied considerably with catalyst and reaction conditions, whereas the long-distance values measured by SAXS were small and varied little with the polymeriza-tion conditions.
KW - MALDI TOF MS
KW - Polyglycolide
KW - Crystalinity
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-598221
DO - https://doi.org/10.1002/pat.6365
VL - 35
IS - 4
SP - 1
EP - 10
PB - John Wiley & Sons Ltd.
AN - OPUS4-59822
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Villajos Collado, José Antonio
A1 - Bienert, M.
A1 - Gugin, Nikita
A1 - Emmerling, Franziska
A1 - Maiwald, Michael
T1 - A database to select affordable MOFs for volumetric hydrogen cryoadsorption considering the cost of their linkers
N2 - Physical adsorption at cryogenic temperature (cryoadsorption) is a reversible mechanism that can reduce the pressure of conventional compressed gas storage systems. Metal–organic framework (MOF) materials are remarkable candidates due to the combination of high specific surface area and density which, in some cases, provide a high volumetric storage capacity. However, such extensive use of MOFs for this application requires the selection of affordable structures, easy to produce and made from feasible metallic and organic components. Herein, we introduce a MOF database detailing the crystallographic and porous properties of 3600 existing MOFs made from industrially relevant metals and their organic composition. The comparison of the available minimum costs of linkers allowed the creation of a database to select affordable structures with high potential for volumetric hydrogen storage by cryoadsorption, considering their composition based on individual or mixed building blocks. A user inter� face, available online, facilitates the selection of MOFs based on the properties or names of structures and linkers.
KW - MOF´s
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-583619
DO - https://doi.org/10.1039/d3ma00315a
VL - 4
IS - 18
SP - 4226
EP - 4237
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-58361
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Martins, Inês C.B.
A1 - Al-Sabbagh, Dominik
A1 - Meyer, Klas
A1 - Maiwald, Michael
A1 - Scholz, G.
A1 - Emmerling, Franziska
T1 - Insight into the Structure and Properties of Novel Imidazole-Based Salts of Salicylic Acid
N2 - The preparation of new active pharmaceutical ingredient (API) multicomponent Crystal forms, especially co-crystals and salts, is being considered as a reliable strategy to improve API solubility and bioavailability. In this study, three novel imidazole-based salts of the poorly water-soluble salicylic acid (SA) are reported exhibiting a remarkable improvement in solubility and dissolution rate properties. All structures were solved by powder X-ray diffraction. Multiple complementary techniques were used to solve co-crystal/salt ambiguities: density functional Theory calculations, Raman and 1H/13C solid-state NMR spectroscopies. In all molecular salts, the Crystal packing interactions are based on a common charged assisted +N-H SA)...O-(co-former) hydrogen bond interaction. The presence of an extra methyl group in different positions of the co-former, induced different supramolecular arrangements, yielding salts with different physicochemical properties.
All salts present much higher solubility and dissolution rate than pure SA. The most promising results were obtained for the salts with imidazole and 1-methylimidazole co-formers.
KW - Salicylic acid
KW - Imidazole
KW - Salts
KW - Powder X-ray diffraction
KW - SsNMR
KW - DFT
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-502825
DO - https://doi.org/10.3390/molecules24224144
VL - 24
IS - 22
SP - 4144
PB - MDPI
AN - OPUS4-50282
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Darvishi Kamachali, Reza
A1 - Wallis, Theophilius
A1 - Ikeda, Yuki
A1 - Saikia, U.
A1 - Ahmadian, A.
A1 - Liebscher, C.
A1 - Hickel, Tilmann
A1 - Maaß, Robert
T1 - Giant segregation transition as origin of liquid metal embrittlement in the Fe-Zn system
N2 - A giant Zn segregation transition is revealed using CALPHAD-integrated density-based modeling of segregation into Fe grain boundaries (GBs). The results show that above a threshold of only a few atomic percent Zn in the alloy, a substantial amount of up to 60 at.% Zn can segregate to the GB. We found that the amount of segregation abruptly increases with decreasing temperature, while the Zn content in the alloy required for triggering the segregation transition decreases. Direct evidence of the Zn segregation transition is obtained using high-resolution scanning transmission electron microscopy. Base on the model, we trace the origin of the segregation transition back to the low cohesive energy of Zn and a miscibility gap in Fe-Zn GB, arising from the magnetic ordering effect, which is confirmed by ab-initio calculations. We also show that the massive Zn segregation resulting from the segregation transition greatly assists with liquid wetting and reduces the work of separation along the GB. The current predictions suggest that control over Zn segregation, by both alloy design and optimizing the galvanization and welding processes, may offer preventive strategies against liquid metal embrittlement.
KW - CALPHAD
KW - Microstructure Design
KW - Grain boundary engineering
KW - Steels
KW - Density-based Model
KW - Segregation Engineering
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-584292
DO - https://doi.org/10.1016/j.scriptamat.2023.115758
SN - 1359-6462
SN - 1872-8456
VL - 238
SP - 1
EP - 5
PB - Elsevier
CY - Amsterdam
AN - OPUS4-58429
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kricheldorf, H.
A1 - Weidner, Steffen
A1 - Scheliga, F.
T1 - Polycondensation of poly(L-lactide) alkyl esters combined with disproportionation and symproportionation of the chain lengths
N2 - Ring-opening polymerizations (ROPs) of l-lactide (LA) were performed with ethyl l-lactate or 11-bromoundecanol as initiators (In) and tin(II) ethyl hexanoate (SnOct2) as catalyst (Cat) using four different LA/In ratios (20/1, 40/1, 60/1, and 100/1). One series of ROPs was conducted in bulk at 120 °C, yielding PLAs with low dispersities (Ð ~ 1.2–1.4), and a second series was conducted in bulk at 160 °C, yielding higher dispersities (Ð ~ 1.3–1.9). Samples from both series were annealed for 1 or 14 days at 140 °C in the presence of SnOct2. Both polycondensation and disproportionation reactions occurred, so that all four samples tended to form the same type of molar mass distribution below 10,000 Da, regardless of their initially different number average molar masses (Mn). Both initiators gave nearly identical results. The thermodynamic control of all reversible transesterification processes favored the formation of crystallites composed of chains with a Mn around 3500–3700, corresponding to a crystal thickness of 10–13 nm.
KW - Polylactide
KW - MALDI-TOF MS
KW - Crystalinity
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-600081
DO - https://doi.org/10.1002/pol.20240118
SN - 2642-4150
SP - 1
EP - 12
PB - Wiley
AN - OPUS4-60008
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Dalgic, Mete-Sungur
A1 - Weidner, Steffen
T1 - Solvent-free sample preparation for matrix-assisted laserdesorption/ionization time-of-flight mass spectrometry ofpolymer blends
N2 - Solvent-free sample preparation offers some advantages over solvent-based techniques, such as improved accuracy, reproducibility and sensitivity, for matrix-assisted laser desorption/ionization (MALDI) analysis. However, little or no information is available on the application of solvent-free techniques for the MALDI analysis of polymer blends. Solvent-free sample preparation by ball milling was applied with varying sample-to-matrix ratios for MALDI time-of-flight mass spectrometry analysis of various polymers, including polystyrenes, poly(methyl methacrylate)s and poly(ethylene glycol)s. The peak intensity ratios were compared with those obtained after using the conventional dried droplet sample preparation method. In addition, solvent-assisted milling was also applied to improve sample homogeneities.
Depending on the sample preparation method used, different peak intensity ratios were found, showing varying degrees of suppression of the signal intensities of higher mass polymers. Ball milling for up to 30 min was required to achieve constant intensity ratios indicating homogeneous mixtures. The use of wet-assisted grinding to improve the homogeneity of the blends was found to be disadvantageous as it caused partial degradation and mass-dependent segregation of the polymers in the vials.The results clearly show that solvent-free sample preparation must be carefully considered when applied to synthetic polymer blends, as it may cause additional problems with regard to homogeneity and stability of the blends.
KW - MALDI TOF MS
KW - Sample preparation
KW - Polymer blends
KW - Solvent-free
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-598570
DO - https://doi.org/10.1002/rcm.9756
SN - 0951-4198
VL - 38
IS - 12
SP - 1
EP - 9
PB - Wiley online library
AN - OPUS4-59857
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schlögl, Johanna
A1 - Goldammer, Ole
A1 - Bader, Julia
A1 - Emmerling, Franziska
A1 - Riedel, Sebastian
T1 - Introducing AFS ([Al(SO3F)3]x) – a thermally stable, readily available, and catalytically active solid Lewis superacid
N2 - This paper introduces the thermally stable, solid Lewis superacid aluminium tris(fluorosulfate) (AFS), that is easy-to-synthesize from commercially available starting materials. Its applicability, e.g. in catalytic C–F bond activations, is shown.
KW - Lewis Acid
KW - C-F activation
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-601001
DO - https://doi.org/10.1039/D4SC01753F
SN - 2041-6520
SP - 1
EP - 7
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-60100
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Dittmar, Stefan
A1 - Ruhl, Aki S.
A1 - Altmann, Korinna
A1 - Jekel, Martin
T1 - Settling Velocities of Small Microplastic Fragments and Fibers
N2 - There is only sparse empirical data on the settling velocity of small, non-buoyant microplastics thus far, although it is an important parameter governing their vertical transport within aquatic environments. This study reports the settling velocities of 4031 exemplary microplastic particles. Focusing on the environmentally most prevalent particle shapes, irregular microplastic fragments of four different polymer types (9–289 µm) as well as five discrete length fractions (50–600 µm) of common nylon and polyester fibers were investigated, respectively. All settling experiments were carried out in quiescent water using a specialized optical imaging setup. The method has been previously validated in order to minimize disruptive factors, e.g. thermal convection or particle interactions, and thus enable the precise measurements of the velocities of individual microplastic particles (0.003–9.094 mm/s). Based on the obtained data, ten existing models for predicting a particle’s terminal settling velocity were assessed. It is concluded that models, which were specifically deduced from empirical data on larger microplastics, fail to provide accurate predictions for small microplastics. Instead, a different approach is highlighted as a viable option for computing settling velocities across the microplastics continuum in terms of size, density and shape.
KW - Microplastics
KW - Microplastic fibers
KW - Settling velocity
KW - Sinking velocity
KW - Sedimentation
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597455
DO - https://doi.org/10.1021/acs.est.3c09602
SN - 0013-936X
VL - 58
IS - 14
SP - 6359
EP - 6369
PB - American Chemical Society (ACS)
AN - OPUS4-59745
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Sieg, Holger
A1 - Schaar, Caroline
A1 - Fouquet, Nicole
A1 - Böhmert, Linda
A1 - Thünemann, Andreas
A1 - Braeuning, Albert
T1 - Particulate iron oxide food colorants (E 172) during artificial digestion and their uptake and impact on intestinal cells
N2 - Iron oxide of various structures is frequently used as food colorant (E 172). The spectrum of colors ranges from yellow over orange, red, and brown to black, depending on the chemical structure of the material. E 172 is mostly sold as solid powder. Recent studies have demonstrated the presence of nanoscaled particles in E 172 samples, often to a very high extent. This makes it necessary to investigate the fate of these particles after oral uptake. In this study, 7 differently structured commercially available E 172 food colorants (2 x Yellow FeO(OH), 2 x Red Fe2O3, 1 x Orange Fe2O3 + FeO(OH) and 2 x Black Fe3O4) were investigated for particle dissolution, ion release, cellular uptake, crossing of the intestinal barrier and toxicological impact on intestinal cells. Dissolution was analyzed in water, cell culture medium and artificial digestion fluids. Small-angle X-ray scattering (SAXS) was employed for determination of the specific surface area of the colorants in the digestion fluids. Cellular uptake, transport and toxicological effects were studied using human differentiated Caco-2 cells as an in vitro model of the intestinal barrier. For all materials, a strong interaction with the intestinal cells was observed, albeit there was only a limited dissolution, and no toxic in vitro effects on human cells were recorded.
KW - Toxicology
KW - Nanoparticles
KW - Small-angle X-ray scattering
KW - SAXS
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-593935
DO - https://doi.org/10.1016/j.tiv.2024.105772
VL - 96
SP - 1
EP - 12
PB - Elsevier BV
AN - OPUS4-59393
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Chowdhary, S.
A1 - Schmidt, R. F.
A1 - Sahoo, A. K.
A1 - tom Dieck, T.
A1 - Hohmann, T.
A1 - Schade, B.
A1 - Brademann-Jock, Kerstin
A1 - Thünemann, Andreas
A1 - Netz, R. R.
A1 - Gradzielski, M.
A1 - Koksch, B.
T1 - Rational design of amphiphilic fluorinated peptides: evaluation of self-assembly properties and hydrogel formation
N2 - Advanced peptide-based nanomaterials composed of self-assembling peptides (SAPs) are of emerging interest in pharmaceutical and biomedical applications. The introduction of fluorine into peptides, in fact, offers unique opportunities to tune their biophysical properties and intermolecular interactions. In particular, the degree of fluorination plays a crucial role in peptide engineering as it can be used to control the characteristics of fluorine-specific interactions and, thus, peptide conformation and self-assembly. Here, we designed and explored a series of amphipathic peptides by incorporating the fluorinated amino acids (2S)-4-monofluoroethylglycine (MfeGly), (2S)-4,4-difluoroethylglycine (DfeGly) and (2S)-4,4,4-trifluoroethylglycine (TfeGly) as hydrophobic components. This approach enabled studying the impact of fluorination on secondary structure formation and peptide self-assembly on a systematic basis. We show that the interplay between polarity and hydrophobicity, both induced differentially by varying degrees of side chain fluorination, does affect peptide folding significantly. A greater degree of fluorination promotes peptide fibrillation and subsequent formation of physical hydrogels in physiological conditions. Molecular simulations revealed the key role played by electrostatically driven intra-chain and inter-chain contact pairs that are modulated by side chain fluorination and give insights into the different self-organization behaviour of selected peptides. Our study provides a systematic report about the distinct features of fluorinated oligomeric peptides with potential applications as peptide-based biomaterials.
KW - Small-angle X-ray scattering
KW - SAXS
KW - Amyloid
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-553504
DO - https://doi.org/10.1039/D2NR01648F
SN - 2040-3364
VL - 14
IS - 28
SP - 10176
EP - 10189
PB - Royal Society of Chemistry
AN - OPUS4-55350
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Dhamo, Lorena
A1 - Carulli, F.
A1 - Nickl, Philip
A1 - Wegner, Karl David
A1 - Hodoroaba, Vasile-Dan
A1 - Würth, Christian
A1 - Brovelli, S.
A1 - Resch-Genger, Ute
T1 - Efficient luminescent solar concentrators based on environmentally friendly Cd-free ternary AIS/ZnS quantum dots
N2 - Luminescent solar concentrators (LSC) allow to obtain renewable energy from building integrated photovoltaic systems. As promising efficient and long-term stable LSC fluorophores semiconductor nanocrystals like Quantum dots (QDs) with size and composition tunable optoelectronic properties have recently emerged. The most popular II/VI or IV/VI semiconductor QDs contain, however, potentially hazardous cadmium or lead ions, which is a bottleneck for commercial applications. A simple aqueous based, microwaveassisted synthesis for environmentally friendly and highly emissive AgInS2/ ZnS QDs is developed using 3-mercaptopropionic acid (MPA) and glutathione (GSH) and their incorporation into polylaurylmethacrylate (PLMA) polymer slabs integrable in LSC devices (10.4 × 10.4 × 0.2 cm3, G = 12.98).
With this simple approach, optical power efficiencies (OPE) of 3.8% and 3.6% and optical quantum efficiencies (OQE) of 24.1% and 27.4% are obtained, which are among the highest values yet reported.
KW - Solar energy
KW - Solar concentrator
KW - Quantum dots
KW - Advanced material
KW - Quantum yield
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-529735
DO - https://doi.org/10.1002/adom.202100587
SN - 2195-1071
SN - 0935-9648
VL - 9
IS - 17
SP - 1
EP - 8
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-52973
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Navarro, L.
A1 - Thünemann, Andreas
A1 - Klinger, D.
T1 - Solvent Annealing of Striped Ellipsoidal Block Copolymer Particles: Reversible Control over Lamellae Asymmetry, Aspect Ratio, and Particle Surface
N2 - Solvent annealing is a versatile tool to adjust the shape and morphology of block copolymer (BCP) particles. During this process, polar solvents are often used for block-selective swelling. However, such water-miscible solvents can induce (partial) solubilization of one block in the surrounding aqueous medium, thus, causing complex structural variations and even particle disassembly. To reduce the complexity in morphology control, we focused on toluene as a nonpolar polystyrene-selective solvent for the annealing of striped polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) ellipsoids. The selective stretching of PS chains produces unique asymmetric lamellae structures, which translate to an increase in the particle aspect ratio after toluene evaporation. Complete reversibility is achieved by changing to chloroform as a nonselective solvent. Moreover, surfactants can be used to tune block-selective wetting of the particle surface during the annealing; for example, a PS shell can protect the internal lamellae structure from disassembly. Overall, this versatile postassembly process enables the tailoring of the structural features of striped colloidal ellipsoids by only using commercial BCPs and solvents.
KW - Small-angle X-ray scattering
KW - SAXS
KW - Nanoparticle
KW - Polymer
PY - 2022
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543731
DO - https://doi.org/10.1021/acsmacrolett.1c00665
VL - 11
IS - 3
SP - 319
EP - 335
PB - American Chemical Society
AN - OPUS4-54373
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -