Current Topics in Polymer Research
Forthcoming Events
The seminars "Current Topics in Polymer Research" (Polymer and Soft Matter Seminars) will take place on Tuesdays at 4.15 pm in seminar room 1.27 at Von-Danckelmann-Platz 4.
25.06.2024 / 18.06.2024 / 11.06.2024 / 04.06.2024 / 14.05.2024 / 30.04.2024 / 23.04.2024 / 16.04.2024
Thu, 25.06.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Prof. Dr. Pieter Lemstra
Plempolco B.V. (The Netherlands)
Thu, 18.06.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Prof. Dr. Pol Besenius
Johannes Gutenberg University Mainz
Thu, 11.06.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
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Prof. Dr. Dennis Kurzbach
University of Vienna (Austria)
Di, 04.06.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Prof. Dr. Arash Nikoubashman
Leibniz-Institut für Polymerforschung Dresden and Technical University Dresden, Germany
Plastic life: What polymer physics can teach us about disordered proteins
The discovery of intrinsically disordered proteins (IDPs) has heralded a paradigm shift in molecular biology away from the principle of ”form follows function”. These IDPs can form biomolecular condensates that fulfill numerous functions in living cells, e.g., signal transduction, stress response and controlled reactions. Due to the conceptual similarities between IDPs and classical polymers, physics-based theories and computer simulations can help to understand, predict and engineer the static and dynamic properties of naturally occurring and synthetic IDPs. In this talk, I will present selected insights we have gained from coarse-grained molecular simulations, and discuss the intricacies and limitations of the underlying models. Key findings include that IDPs inherently exhibit heterogeneous interactions that are weak and distributed along the chain contour, and that IDPs collapse at the condensate-water interface and are tangentially oriented. Further, we discovered that the phase behavior and materials properties of condensates can be deducted with great accuracy from the conformations of single IDP chains in solution.
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Thu, 14.05.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
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Prof. Dr. Stephen Schrettl
Technical University of Munich
Thu, 30.04.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
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Jun.-Prof. Dr. Valerian Hirschberg
Clausthal University of Technology
Synthesis, rheology and constitutive modelling of complex polymer model systems
Understanding the effect of branching on the melt rheological properties in shear and elongation is of fundamental interest since the dawn of polymer science and allows to engineer material properties, with the classical example for Polyethylene of HDPE and LDPE. Besides the number and the molecular weight of the arms, the exact location of the branching points, i.e., the exact architecture of the polymer (its topology) is key to control shear and extensional rheological properties.
Continuing the pom-pom story from a purely theoretical approach, about twenty low-disperse, polystyrene samples with a pom-pom topology were synthesized with optimized synthetic routes via a combination of anionic polymerization and grafting onto, in the scale of up to 300 g per model system. The molecular parameters of the pom-poms such as molecular weight of the backbone (MW,bb = 100 - 400 kg/mol), of the arms (MW,a = 2.5 – 300 kg/mol) and the arm number at each end (q = 5-30) are systematically varied. The shear and elongational behaviour are investigated experimentally and modelled with the pom-pom and the Hierarchical Multi-mode Molecular Stress Function (HMMSF) model.
Shear thinning is found in small amplitude oscillatory shear (SAOS) measurements, depending on MW,a, the backbone volume fraction and backbone self-entanglement. The zero-shear viscosity and the diluted modulus as a function of the backbone volume fraction are analysed. Additionally, criteria to predict backbone self-entanglement based on the effective backbone entanglement are investigated and compared with double reputation theory. The results of the pom-poms are compared with literature data of combs. In elongational flow, very high strain hardening factors > 100 are found. Following the pom-pom model and the Considère criterium, the SHF can be predicted based exclusively on the arm number q if the backbone is self-entangled by a factor of . For combs and pom-poms with similar molecular properties, similar SHF are obtained in elongational flow.
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Thu, 23.04.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
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Prof. Dr. Johannes C. Brendel
University of Bayreuth
Tailored design of reactive polymers and nanostructures
Nature presents numerous examples for responsive structures, which react to subtle changes in their environment. In our group, various functional monomers and polymers are synthesized which react selectively to specific stimuli such as an oxidative environment or changes in pH. In the latter case, we realized amino-based polymers, which are selectively protonated in the biological most interesting range of pH 5-8. In another example, we utilize thioether groups to trigger a time-delayed release and degradation under oxidative conditions.
Another focus of our research is the controlled assembly of these functional polymers into nanostructures of specific shapes. Therefore, we investigate approaches such as polymerization induced self-assembly (PISA) or directed supramolecular interactions to guide the assembly of the functional polymer building blocks into different nanostructures. In the latter case, directing hydrogen bonds are employed to drive the assembly of funcionalized polymers into supramolecular bottlebrush-like fibres. The assembly follows a nucleation-growth mechanism which allows to tune the length of the fibers.
Meeting-ID: 2780 086 2329
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Tue, 16.04.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
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Prof. Dr. Sijbren Otto
Centre for Systems Chemistry, Stratingh Institute, University of Groningen (The Netherlands)
Oligomerization and Self-Assembly in the De-Novo Synthesis of Life
How the immense complexity of living organisms has arisen is one of the most intriguing questions in contemporary science. We have started to explore experimentally how organization and function can emerge from complex molecular networks in aqueous solution. 1 We focus on networks of molecules that can interconvert, to give mixtures that can change their composition in response to external or internal stimuli. Noncovalent interactions within molecules in such mixtures can lead to the formation of foldamers.2,3 In contrast, molecular recognition between molecules in such mixtures leads to their mutualstabilization, which drives the synthesis of more of the privileged structures (Figure 1). As the assembly process drives the synthesis of the very molecules that assemble, the resulting materials can be considered to be self-synthesizing. Intriguingly, in this process the assembling molecules are replicating themselves, where replication is driven by self-recognition of these molecules in the dynamic network.4 The selection rules that dictate which (if any) replicator will emerge from such networks are starting to become clear. 5 We have also witnessed spontaneous differentiation (a process akin to speciation as it occurs in biology) in a system made from a mixture of two building blocks.6 When such systems are operated under far-from-equilibrium flow conditions, adaptation of the replicators to a changing environment can occur. Replicators that are able to catalyse reactions other than their own formation have also been obtained, representing a first step towards metabolism.7,8 Rudimentary Darwinian evolution of purely synthetic molecules has also been achieved 9 and the prospect of synthesizing life de-novo is
becoming increasingly realistic. 10
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87
Past Events
Thu, 23.01.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
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Prof. Dr. Seema Agarwal
Faculty of Biology, Chemistry and Earth Science, Macromolecular Chemistry, University of Bayreuth
Plastic pollution: Role of sustainable biodegradable polymers
The extreme stability of polymers has challenged society with the accumulation of plastic waste and its management worldwide. Whether biodegradable polymers can be one of the solutions to the problem of plastic waste is a question very often raised in this context. The answer is not straightforward as several aspects need to be considered regarding environmental sustainability, acceptability, and degradability in the complex natural environment. The present talk will discuss the present scenario of the environmental acceptability of biodegradable polymers and the opportunities and challenges they offer regarding solving the problem of plastic pollution and their impact on the environment.
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87
Thu, 16.01.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Jun.-Prof. Dr. Christian Franke
Friedrich Schiller University Jena, Germany
Nanometer Resolution and Single-Molecule Sensitivity -
Super-Resolution Microscopy for Polymer Research
Fluorescence based super-resolution microscopy methods, such as single-molecule localization microscopy (SMLM), have emerged as the prime tool to investigate structure-function relationships of cellular organelles with three-dimensional nanometer resolution and single-molecule sensitivity. The unique nature of SMLM, i.e. pinpointing molecular identities, has allowed a huge array of discoveries in the life sciences. Besides the often prominently featured ‘pretty pictures’ with unmatched spatial resolution of down to 10 nm, SMLM offers the unique feature of analyzing the localization data itself, which is commonly applied to cluster analyses, thus probing spatial inhomogeneities in the target structure with distinct molecular identities based on their spectral fingerprint, including anisotropy.
Although the main field of application of SMLM and related super-resolution techniques lies in cell biology and connected clinical research, its unique features regarding the multi-colour, nanometric sampling of the target structure, topology and homogeneities in large fields of view and volumes yield huge potential in polymer research. For instance, we currently apply SMLM to study the nanoscale structure-function relationship of polymeric nanoparticles, utilized for drug delivery. Here, the goal is to correlate the properties of the polymeric particle to their intracellular fate, to yield a feedback loop to finally design nanoparticles of highest efficacy and lowest toxicity.
Recently, we also started to apply SMLM to more fundamental polymeric systems, e.g. the nanoscale architecture of polymeric hydrogels in different states of hydration. SMLM usually requires aqueous environments, due to the demanding requirements regarding the photo-physical properties of commonly used dyes. We thus established a novel approach, at the same time enabling SMLM in solid state polymeric, i.e. dry, environments, and utilizing these structures as novel reference structures for super-resolution microscopy. This opens up entirely new avenues for SMLM analyses of visualizing polymer matrices with nanometer resolution and changes therein in context of potential ligands or changing environmental conditions.
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87
Thu, 09.01.2024
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
PD Dr. Robert Göstl
DWI – Leibniz Institute for Interactive Materials, Aachen, Germany
and RWTH Aachen University, Germany
From force-reporting to force-resistant: using mechanochemistry to understand polymer materials
One of the grand scientific challenges of our time is how the remarkable properties of matter emerge from the complex correlations of their molecular constituents. We perform research adhering to this principle by following the results of mechanical stress and strain on macromolecular materials, which often requires to survey large samples with molecular level resolution due to the multiscale nature of force.
To do so, we firstly design and synthesize molecular optical force probes and the respective macromolecular materials made from them in a transdisciplinary approach.[1] We mainly employ Diels-Alder adducts of π-extended anthracenes and maleimides reporting over covalent bond scission events due to their sensitive nature and facile tunability of their optical properties.[2,3]
Secondly, we use these mechanofluorophores to investigate the mechanical behavior of complex and non-uniform high-performance polymers, such as rubbers and composites, and soft matter, e.g., hydrogels and colloidal hydrogel networks, in detail developing novel methodologies. From these experiments, we aim to draw conclusions over the behavior of these materials under force.[4,5]
Eventually, we strive to use the insights gained from this to develop materials with improved mechanical properties by, e.g., introducing pathways to dissipate stresses at the locations where they are most critical or to self-reinforce or by the activation of latent functional motifs to perform mechanically activated chemical reactions.[6]
References
[1] S. He, M. Stratigaki, S. P. Centeno, A. Dreuw, R. Göstl, Chem. Eur. J. 2021, 27, 15889–15897.
[2] D. Yildiz, C. Baumann, A. Mikosch, A. J. C. Kuehne, A. Herrmann, R. Göstl, Angew. Chem. Int. Ed. 2019, 58, 12919–12923.
[3] C. Baumann, M. Stratigaki, S. P. Centeno, R. Göstl, Angew. Chem. Int. Ed. 2021, 60, 13287–13293.
[4] E. Izak-Nau, S. Braun, A. Pich, R. Göstl, Adv. Sci. 2022, 9, 2104004.
[5] S. He, S. Schog, Y. Chen, Y. Ji, S. Panitz, W. Richtering, R. Göstl, Adv. Mater. 2023, 35, 2305845.
[6] D. Campagna, R. Göstl, Angew. Chem. Int. Ed. 2022, 61, e202207557.
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87
Thu, 14.12.2023 - Special date
14:15 Uhr im Seminarraum 1.02 Von-Seckendorff-Platz 1, 06120 Halle
Prof. Dr. Alexey V. Lyulin
Soft Matter and Biological Physics, Department of Applied Physics and Science Education, Technische Universiteit Eindhoven, 5600 MB, Eindhoven, The Netherlands and Center for Computational Energy Research, Technische Universiteit Eindhoven, 5600 MB, Eindhoven, The Netherlands
Multiscale modelling of the glass transition in Nafion membranes for
perspective flow and fuel batteries
Nafion is a commonly used polyelectrolyte membrane (PEM) in fuel cells and flow batteries. Nanocomposites of Nafion are used to enhance temperature resistance and proton conductivity. The properties of hydrated membranes, and the water influence on Nafion glassy behavior is very important. We first report molecular-dynamics simulations of Nafion films of different thicknesses between two potential walls of variable wettability [1]. The water cluster sizes showed an increase with film thickness for the high wettability cases, in agreement with SAXS experiments. The in-plane water diffusion was considerably enhanced for the high wettability walls. We report the modelling of the annealing effects on both structure, dynamics and electric conductivity of the membranes. We observe [2] strong antiplasticization effect and increase in the glass-transition temperature upon hydration. The hydrophilic channels evolution upon annealing and associated changes in ion diffusion and electric conductivity will be discussed. Large scale Dissipative Particle Dynamics simulations were carried out as well to study the temporal evolution of the water-PEM interface as a function of the PEM side-chain length.
Acknowledgements
This work was done as a part of the FOM-SHELL 15CSER13 research project and was carried out on the Dutch national e-infrastructure with the support of SURF Cooperative. AVL and AV both thank DUO-India Fellowship Program for the possibility to visit and work at IISER Pune and TU Eindhoven, correspondingly. Arun Venkatnathan thanks DST Nanomission Thematic Unit (SR/NM/TP-13/2016(G)).
References
[1] S. Sengupta, A. V. Lyulin, J. Phys. Chem. B, 122, 6107-6119, 2018.
[2] A. V. Lyulin S. Sengupta, A. Varghese, P. Komarov and A. Venkatnathan, ACS Appl. Polym. Mater., 2, 5058-5066, 2020.
Tue, 12.12.2023
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Prof. Dr. Andreas Herrmann
Leibniz Institute for Interactive Materials DWI, Aachen, Germany
RWTH Aachen, Germany
Sonopharmacology and Sonogenetics: Activating drugs, proteins and genes by ultrasound
Remote controlling biological systems is an exciting endeavour because it is the offspring for new therapies and allows answering fundamental biological questions. In this context, the field of optogenetics has enabled the understanding of neural circuits and disorders.[1,2] However, current optogenetic techniques are hampered by the low penetration of light into tissue and hence often require invasive surgical procedures to deliver photons to target cells. Therefore, ultrasound (US) was used as alternative trigger since US can deeply penetrate tissue with high spatiotemporal control and has been safely applied in the clinic for many decades.[3] Our group has developed general molecular technologies to activate drugs, proteins and nucleic acids by US employing principles from polymer mechano-chemistry.[4,5] Two types of mechano-sensitive carriers have been discovered, i.e. high molar mass polynucleic acid aptamers and colloidal hydrogel microbubbles. Polynucleic acids fabricated by enzymatic reactions undergo covalent and non-covalent bond cleavage induced by shear forces originating from US-induced cavitation bubbles. These nucleic acid carriers harbouring different bioactive payloads allow the activation of small bioactive molecules and drugs that can initiate gene expression, kill pathogens or cure diseases.[4,5] Moreover, the activation of thrombin by US allows the general control over protein activity in combination with split inteins.[6] A particular emphasis is paid to reducing US energies to make these sonogenetic and sonopharmacological systems compatible with living matter.[7] In this realm, microbubbles containing a hydrogel shell with embedded mechanophores were developed.[8]
References:
[1] Haubensak W, Kunwar PS, Cai H, Ciocchi S, Wall NR, Ponnusamy R, Jonathan Biag, Dong H-W, Deisseroth K, Callaway EM, Fanselow MS, Lüthi A, Anderson DJ, Nature (2010) 468: 270.
[2] Kravitz AV, Freeze BS, Parker PR, Kay K, Thwin MT, Deisseroth K, Kreitzer AC, Nature (2010) 466: 622.
[3] Wang T, Wang H, Pang G, He T, Yu P, Cheng G, Zhang Y, Chang J, ACS Appl. Mat. & Interf. (2020) 12: 56692.
[4] Paul A, Warszawik EM, Loznik M, Boersma AJ, Herrmann A, Angew. Chem. Int. Ed. (2020) 59, 20328.
[5] Huo S, Zhao P, Shi Z, Zou M, Yang X, Warszawik E, Loznik M, Göstl G, Herrmann A, Nat. Chem. (2021) 13: 131.
[6] Zhao P, Huo S, Fan J, Chen J, Kiessling F, Boersma AJ, Göstl R, Herrmann A, Angew. Chem. Int. Ed. (2021) 60, 14707.
[7] Yildiz D, Göstl R, Herrmann A, Chem. Sci. (2022) 13: 13708.
[8] Xuan M, Fan J, Ngoc Khiêm V, Zou M, Brenske KO, Mourran A, Vinokur R, Zheng L, Itskov M, Göstl R, Herrmann A, Adv. Mat. (2023) published online doi.org/10.1002/adma.202305130.
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87
Tue, 05.12.2023
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Prof. Dr. Felix H. Schacher
Friedrich Schiller University Jena, Germany
Can polymers do magic? - The role(s) of polymeric templates in light-driven catalysis
Polymers are a versatile class of materials with almost unlimited combinations of functional groups being present in close proximity. This in combination with a widely tunable solubility has enabled quite a range of examples where building blocks for light-driven catalysis (i.e., photosensitizers and catalysts) are immobilized using either covalent anchoring or non-covalent interactions. During recent years, we have developed different soft matter matrices for either light-driven hydrogen evolution (HER) or water oxidation (WOC) based on unimolecular graft copolymers, block copolymer micelles, hydrogels, or nanoporous block copolymer membranes. In all cases, close proximity of the immobilized building blocks facilitated light-driven reactivity, but we also observed additional effects during our studies, such as prolonged lifetime of photosensitizers, altered degradation pathways, or the possibility to repair / exchange catalysts or sensitizers. In addition, some effects imply that – especially in case of polyampholytic graft copolymers – the polymeric matrix is also involved in charge transport, presumably due to the high charge density present along the polymer backbone. Altogether, in this contribution we try to derive some general guidelines for the design of (charged) soft matter matrices for light-driven catalysis.
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87
Tue, 28.11.2023
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
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Dr. Mehdi D. Davari
Leibniz Institute of Plant Biochemistry, Germany
Synergizing Science and Innovation: Developing Sustainable Detergents with Computational Modeling and Experiments
The modern laundry detergents present a complex interplay of diverse components - enzymes, surfactants, builders, bleaching agents, and minor additives, all synergistically engineered to remove stains. A fundamental comprehension of the molecular interactions between these components stands as a pivotal avenue for advancing the formulation, performance, and sustainability of detergent industry products.
In this presentation, I will delve into the research conducted within the Henkel Innovation Campus for Advanced and Sustainable Technologies (HICAST) between 2014 and 2019 at RWTH Aachen University. HICAST's primary focus was on developing novel, sustainable laundry detergents by unlocking the mysteries surrounding interactions among detergent components. Our primary objective was to deeply probe the molecular dynamics governing the boosting of protease activity in detergent enzymes when interacting with polymers and surfactants. Our multidisciplinary approach, integrating computational modeling (atomistic and coarse-grained molecular dynamic simulations), alongside colorimetric analysis and biophysical characterization methods (CD, FCS, ITC, and DLS), and innovative enzyme engineering, outlined a promising workflow. This methodology provided us with profound molecular insights into the mechanisms that govern this enhancement and effectively elevate detergent performance. Importantly, the profound understanding of the fundamental principles underpinning increased protease performance holds promise for applications across diverse detergent enzymes. It is poised to revolutionize the engineering of enzymes, polymers, and surfactants compositions in the realm of modern laundry detergents.
This presentation offers a glimpse into a realm where computational modeling, enzyme engineering, and soft matter engineering converge, opening the door to an era of more sustainable, high-performing detergent formulations.
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87
Tue, 21.11.2023
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Prof. Dr. Karsten Mäder
Martin Luther University Halle-Wittenberg, Institute of Pharmacy, Germany
Biodegradable polyesters for drug delivery: materials and performance
Biodegradable polyesters are important materials for controlled drug delivery. Until now, mainly polylactide (PLA) and poly-(lactide-co-glycolide) (PLGA are used to deliver the drug molecules over several weeks to months. The talk will discuss how material properties and processes, but also the size (nano- vs. micron range) are linked with the control of drug delivery. Despite PLA and PLGA dominate the field until now, they have several drawbacks. The formation of the acidic monomers lactic and glycolic acid leads to the formation of highly acidic microenvironments in vitro and in vivo 1–3 and might cause acylation and degradation of drug molecules prior release 4. It also triggers autocatalytic polymer degradation which leads to the paradox of a faster degradation of larger particles and implants. Acidic microenvironments can be prevented by the use of PEG-PLGA block polymers. Block polymers permit also and better release of hydrophilic drugs, because a zero-order release with no lag time can be achieved 5. The presentation will discuss the monitoring of the polymer microenvironment by EPR spectroscopy and optical imaging. It will also highlight the need for the development of alternative polymers for drug delivery purposes.
References:
1. Mäder, K., Gallez, B., Liu, K. J. & Swartz, H. M. Non-invasive in vivo characterization of release processes in biodegradable polymers by low-frequency electron paramagnetic resonance spectroscopy. Biomaterials17, 457–461 (1996).
2. Liu, Y. & Schwendeman, S. P. Mapping microclimate pH distribution inside protein-encapsulated PLGA microspheres using confocal laser scanning microscopy. Mol. Pharm.9, 1342–1350 (2012).
3. Schädlich, A., Kempe, S. & Mäder, K. Non-invasive in vivo characterization of microclimate pH inside in situ forming PLGA implants using multispectral fluorescence imaging. J. Control. Release179, 52–62 (2014).
4. Lucke, A., Kiermaier, J. & Göpferich, A. Peptide Acylation by Poly(α-Hydroxy Esters). Pharm. Res. 2002 19219, 175–181 (2002).
5. Elena de Souza, L. et al. Has PEG-PLGA advantages for the delivery of hydrophobic drugs? Risperidone as an example. J. Drug Deliv. Sci. Technol.61, 102239 (2020).
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87
Tue, 14.11.2023
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Dr. Martina Delbianco
Max Planck Institute of Colloids and Interfaces, Postdam-Golm, Germany
Synthetic carbohydrate-based materials
Natural biopolymers have inspired the development of synthetic analogues capable of adopting defined conformations and forming programmable three-dimensional architectures. These compounds are mainly based on peptides and nucleic acids, that are well understood at the molecular level. In contrast, the complexity of carbohydrate synthesis and structural analysis have prevented access to synthetic carbohydrates capable of adopting defined geometries. In the Delbianco group, we prepare well-defined oligosaccharides to understand how the primary sequence affects the carbohydrate conformation.1 With multiple analytical techniques, we study the conformation of single carbohydrate chains2 and explore how several carbohydrate molecules aggregate to form a material3. Building on this fundamental knowledge, we present the rational design and synthesis of a glycan adopting a stable secondary structure,4 challenging the common belief that glycans are not capable of folding due to their flexibility. The ability to control the conformation of glycans could lead to the generation of programmable 3-D architectures, with applications in catalysis and nanotechnology.
References:
1. Y. Yu, T. Tyrikos-Ergas, Y. Zhu, G. Fittolani, V. Bordoni, A. Singhal, R. J. Fair, A. Grafmüller, P. H. Seeberger, M. Delbianco, Angew. Chem., Int. Ed. 2019, 58, 1433-7851
2. X. Wu, M. Delbianco, K. Anggara, T. Michnowicz, A. Pardo-Vargas, P. Bharate, S. Sen, M. Pristl, S. Rauschenbach, U. Schlickum, S. Abb, P. H. Seeberger, K. Kern, Nature 2020, 582, 375-378.
3. G. Fittolani, D. Vargová, P. H. Seeberger, Y. Ogawa, M. Delbianco, J. Am. Chem. Soc. 2022, 144, 12469-12475.
4. G. Fittolani, T. Tyrikos-Ergas, Y. Yu, N. Yadav, P.H. Seeberger, J. Jiménez-Barbero, M. Delbianco, Synthesis of a glycan hairpin, Nat. Chem., 2023, 15, 1461
Tue, 07.11.2023
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Dr. Eva von Domaros
Friedrich Schiller University Jena, Germany
Can polymer properties be predicted from theory?
The material class of polymers is not only extremely large and complex. Polymers are important parts of our daily lives as plastics or biopolymers like sugars or the DNA backbone. The theoretical understanding---let alone the prediction---of polymer properties is very demanding. The reason therefore is a combination of polymer characteristics. Very large system sizes that easily reach thousands of repeating subunits are hardly feasible for accurate electronic structure methods such as DFT. Furthermore, in contrast to crystalline compounds, polymers are amorphous and lack periodic symmetry, which can be exploited for crystals in periodic calculations. Theoretical models which are capable of treating these systems necessarily apply approximations such as parameterized force fields and, hence, are less accurate and reliable.
In this presentation, a novel approach to understand and later on predict macroscopic properties of this diverse material class is presented. The so-called Quantum Cluster Equilibrium (QCE) method is based on a statistical approach which allows to transfer highly reliable electronic structure data to macroscopic phases. The QCE method will be introduced and demonstrated at the example of liquid systems. Afterwards, the extension to amorphous systems such as polymers will be demonstrated, and promising applications will be presented. Finally, it will be shown which properties are within the reach of this method and the limitations will be discussed.
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87
Tue, 24.10.2023
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Prof. Dr. Chris McNeill
Monash University, Melbourne, Australia
Resonant Tender X-ray Scattering of Conjugated Polymers
Semiconducting polymers are being developed for application in a wide range of optoelectronic devices including solar cells, LED and transistors. Being polymeric materials they offer advantages over traditional semiconductors including ease of processing and mechanical flexibility. Most semiconducting polymers are semicrystalline, and the way in which polymer chains pack strongly affects their optoelectronic performance. Unlike small molecule crystals whose structure can be directly solved using established crystallographic methods, semiconducting polymers are more disordered meaning that there are not enough diffraction peaks available. To squeeze more information from the diffraction peaks that are present, we have turned to resonant tender X-ray diffraction: By varying the X-ray energy across an elemental absorption edge, variations in diffraction intensity are observed that can provide additional information about molecular packing. Also known as anomalous diffraction, this technique has been applied in other fields such as protein crystallography. As many semiconducting polymers utilise sulfur as heteroatoms, we have studied resonant diffraction effects at the sulfur K-edge in the tender X-ray regime. By performing high resolution energy scans across the sulfur K-edge, we show that spectroscopic information relating to specific bonds and molecular orientation can be discerned in the resonant X-ray diffraction profiles.
Indeed, by understanding the anisotropic X-ray absorption properties of these materials we are able to interpret this data allowing us to distinguish between different crystalline polymorphs and resolve the tilting of the polymer backbone with respect to the unit cell axes. In general our work highlights how the fields of crystallography and spectroscopy can be combined to provide new insights into the molecular packing of weakly ordered soft materials.
Meeting-ID: 2731 781 6143
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Tue, 17.10.2023
16:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
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Prof. Dr. Rameshwar Adhikari
Central Department of Chemistry and Research Centre for Applied Science and Technology (RECAST), Tribhuvan University, Kathmandu, Nepal
Structure-Properties Correlations in poly(butylene adipate -co-terephthalate) Based Compostable Composites
We shed light on the structure-properties correlation of composite materials comprising a biodegradable polymer, the poly(butylene adipate-co-terephthalate) (PBAT), and some natural fibers (such as lignocelluloses, chitosan processed via different routes) and nanofillers (such as multiwalled carbon nanotubes), particularly focusing on mechanical, morphological and electrical properties as well as degradation under soil burial conditions. It was shown that the morphology and mechanical properties of the composites can be tailored over a wide range although the materials were found to be suited for low load bearing applications.
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87
Tue, 10.10.2023
4.15 pm in seminar room 1.27 Von-Danckelmann-Platz 4, 06120 Halle
We try to offer the hybrid option, but cannot guarantee it!
Prof. Dr. Ralf B. Wehrspohn
Microstructure-based Materials Design, Martin Luther University Halle-Wittenberg
(Towards) bio-intelligent materials
The wetting behavior on 2D and 3D surfaces for e.g. polymer processing or nanostructuring is still in detail unknown and difficult to measure since inner surfaces are difficult to characterize. Similarly, hierarchically structured polymer nanostructures or metamaterials with improved mechanical properties exhibit similar problem understanding their detailed behavior.
For understanding wetting behavior as inner polymer nanostructures,
3D microscopy is of utmost importance. Since about 10 years now, 3D X-Rays Microscopy with nanometer resolution is available for
university research. With our microscopic technology, we are able
to understand for the first time the wetting kinetics and the principles of hierarchically structured polymers.
At the end of the seminar, the limits in resolution are discussed and possible ways to circumvent them are presented such as expansion
microscopy.
Meeting-ID: 2731 781 6143
Passwort: bVhRTe5C?87