Invited Talks

Friederike Adams

University of Stuttgart, Germany
Friederike Adam’s webpage

Rare-earth metal-mediated polymerization techniques as versatile tools towards tunable copolymers

Due to their impressive diversity, the application horizon of thermoplastics is extending far beyond the use as ordinary consumer goods. With the shift from commodity plastics to polymers used in high-tech applications, the precise tuning and modification of these materials is a key requirement. Therefore, the optimization of polymerization catalysts plays a significant role in modern polymer chemistry to efficiently produce different polymer architectures and microstructures for fine-tuning of material properties. Well-investigated rare-earth metal (REM) complexes can act as highly active catalysts in two different coordination polymerization types: Ring-opening polymerization (ROP) of lactones and group-transfer polymerization (GTP) of Michael-type vinyl monomers. Modifications of the complexes were performed to enhance catalyst activity, stereoselectivity and to enable the synthesis of functional block copolymers with versatile end-groups. With the development of these new polymers various aspects of modern polymer chemistry were targeted: Biobased and biodegradable, metal-functionalized, and stimuli-responsive, amphiphilic polymers for drug and nucleic acid delivery.

Paolo Arosio

ETH Zürich, Switzerland

Paolo Arosio’s webpage

Kostas Daoulas

Max Planck Institute for Polymer Research Mainz, Germany

Kostas Daoulas’s webpage

Ultra coarse-grained modelling of near-crystalline functional polymers: what can we learn?

Inevitably, large-scale computational studies of structure-property relationships in polymers require simplified models, which achieve the necessary efficiency by mapping large groups of actual atoms on single interaction centers. However, the implementation of ultra coarse-grained models can be also very challenging: the significant simplification of the molecular structure can eliminate features that are, in fact, crucial for structure formation. One important class of materials, where such problems are expected, are functional polymers with backbones comprising aromatic rings and small side chains ─ conjugated polymers are a typical case.

Nevertheless ─ and this is one of the main ideas we plan to convey ─ the perspectives of simplified models in studies of such “board-like” polymers are better than one might initially expect. One reason is that these polymers commonly exhibit pronounced structural disorder [1].  Even their crystalline phases can have large para-crystallinity, whereas one often observes [1,2] only small-scale molecular aggregation and liquid-crystalline mesophases. This structural “noise”, combined with the collective nature of the ordering processes, might mitigate the reduction of microscopic details, rendering simplified models useful for addressing certain questions.

First, we will summarize some simplified models used in generic studies of polymer order, crystallization in particular. We will argue why these approaches are insufficient for board-like functional polymers and highlight some simplified models that have been developed for these materials. Next, we will focus on an approach [3,4] where near crystalline, sanidic, mesophases are described by combining a minimalistic representation of polymer architecture with generic anisotropic potentials. As an application, we will present new simulation results related to studies of texture of P3HT films [5] where face-on and edge-on orientation of crystalline lamellae is favored at the bottom and top surface, respectively. These results highlight the need for understanding the elastic properties of highly ordered, almost crystalline, mesophases.

References

[1] Noriega et al, Nature Mat. 2013, 12, 1038-1044.
[2] Stingelin N., Polym. Int. 2012, 61, 866-873.
[3] Greco C., Melnyk A., Kremer K., Andrienko D., Daoulas K. Ch. Macromolecules 2019, 52, 968-981.
[4] Wood E. L., Greco C., Ivanov D. A., Kremer K., Daoulas K. Ch. J. Phys. Chem. B. 2022, 126, 2285-2298.
[5] Dolynchuk O., Schmode P., Fischer M., Thelakkat M., Thurn-Albrecht T. Macromolecules 2021, 54, 5429-5439.

Oleksandr Dolynchuk

University of Halle, Germany

Oleksandr Dolynchuk’s webpage

Interface-Induced Crystallization in Polymers: From Model Systems to Functional Semiconducting Polymers

Ilja Gunkel

Adolphe Merkle Institute Fribourg, Switzerland

Ilja Gunkel’s webpage

Crystallization helps self assembly: Visualizing grain boundaries in block copolymers

Wolfgang Hoyer

University Düsseldorf, Germany

Wolfgang Hoyer’s webpage

Meytal Landau

Israel Institute of Technology, Israel

Meytal Landau’s webpage

Virulent and Antimicrobial Amyloids in Infections and Neurodegeneration

Amyloids are protein oligomers and fibers which are known mainly in the context of neurodegenerative diseases yet are secreted by species across kingdoms of life to carry out physiological function and help survival and activity. Their function as key virulence factors in microbes has rendered them attractive candidates for structural characterization aimed at discovering novel antivirulence therapeutics. Our laboratory pioneered the atomic-level analysis of bacterial amyloids and eukaryotic functional fibrils involved in cytotoxicity, biofilm structuring, and antibacterial activity. Our findings thus far exposed an extreme structural diversity, extending beyond canonical amyloid cross-β structures, and encoding different activities. In particular, the discovery of a novel class of cross-α amyloid fibrils of toxic peptides presented a unique protein architecture, offered drug targets and leads, and opened a fresh perspective to study amyloid-related toxicity. Moreover, we revealed that amyloids secreted by bacteria show similarities in molecular structures to human amyloids involved in neurodegenerative diseases such as Alzheimer’s and Parkinson’s. This might raise concerns about the involvement of microbes in facilitating these diseases, similar to prion proteins transmitted by contaminated meat that elicit the Creutzfeldt-Jakob disease. In addition, we identified peptides produced across species that provide antimicrobial protection that form amyloid fibrils and determined their first high resolution structures. This amyloid-antimicrobial link proposes a physiological role in neuroimmunity for human amyloids. Such antimicrobial fibrils can facilitate the design of functional and stable nanostructures to serve as a stable coating for medical devices or implants, industrial equipment, food packing and more.

Sébastien Lecommandoux

Bordeaux Institute of Technology, France

Sébastien Lecommandoux’s webpage

Karen Lienkamp

Saarland University, Germany

Karen Lienkamp’s webpage

Bioinspired Polymer Surfaces: From Structure-Property Relationships to Biomedical Applications

Sara Linse

Lund University, Sweden

Sara Linse’s webpage

Secondary nucleation in amyloid formation

Secondary nucleation is a critical step in many self- assembly processes including crystallization and amyloid fibril formation. In several systems, including amyloid β peptide and protein tau from Alzheimer’s disease, α-synuclein from Parkinson’s disease and IAPP from diabetes type II, the process is associated with the generation of toxic species. A molecular level understanding of secondary nucleation may thus be important towards the design of inhibitors to combat these devastating human diseases. Our studies aim find the molecular driving forces that govern secondary nucleation and to understand this process in terms of its composite steps and structural transitions. The talk will give an overview of our current knowledge and unknown aspects about secondary nucleation and aims to open a discussion on how to address this using experiments, simulations and theory.

Georg Meisl

University of Cambridge, United Kingdom

Georg Meisl’s webpage

Rate-limiting processes in protein self-assembly: from the test tube to living systems

In the past decades, the central role of aberrant protein self-assembly has been established in many neurodegenerative diseases. The molecular mechanisms that underlie this process of protein aggregate formation have been studied in detail under controlled in vitro conditions. However, connecting the fundamental physical properties of protein self-assembly to the formation and proliferation of protein aggregates in the brains of affected individuals remains a key challenge in the field. I will show how, starting from a knowledge of the underlying physics, we build simple coarse-grained mathematical models that are able to describe the temporal and spatial distribution of aggregates in the brains of lab animals and human patients, linking back to the underlying molecular processes. These minimal models not only provide a qualitative understanding of the ranges of possible behaviors but also allow quantification of the relative importance of different classes of processes in protein self-assembly in vivo. I will show how the application of these models can establish the mechanism of prion self-replication in mice and identify the rate-limiting process in the appearance of tau aggregates in Alzheimer’s disease.

Günter Reiter

University of Freiburg, Germany

Günter Reiter’s webpage

Stacks of Correlated Lamellar Polymer Crystals

Based on the mechanism of self-induced nucleation, the orientation of polymers in the basal lamellar crystal can propagate to other lamellae growing on top [1,2]. As a result, stacks of crystalline lamellae all having a uniquely oriented shape, referred to as “3D (three-dimensional) single crystals”, can be obtained [3]. Using a rationally designed two-step crystallization approach, we were able to induce the formation of stacks of superposed and uniquely oriented flat-on polymer lamellae exclusively and controllably at the periphery of mono-lamellar polymer crystals [4]. We employed this approach for the formation of a “fence” of stacks of lamellar crystals at the periphery of mono-lamellar stereocomplex single crystals of poly(l-lactide) and poly(d-lactide). The resulting morphology resembled a “pseudo hollow crystal” with an almost empty interior of a size controllable by crystallization time. We believe that the presented growth mechanisms leading to “3D single crystals” can be observed for all crystallizable polymers including block copolymers.

References

[1] H. Zhang, M. Yu, B. Zhang,R. Reiter, M. Vielhauer, R. Mülhaupt, J. Xu, and G. Reiter, Phys. Rev. Lett. 112, 237801 (2014). https://doi.org/10.1103/PhysRevLett.112.237801
[2] S. Majumder, R. Reiter, J. Xu, and G. Reiter, Macromolecules  52, 9665– 9671 (2019).  https://doi.org/10.1021/acs.macromol.9b02120
[3] Z. Guo, S. Yan, and G. Reiter, Macromolecules  54, 10, 4918–4925 (2021). https://doi.org/10.1021/acs.macromol.1c00081
[4] W. Chen, B. Bessif, R. Reiter, J. Xu, and G. Reiter, Macromolecules 54, 8135–8142 (2021).  https://doi.org/10.1021/acs.macromol.1c01390

Alicyn Rhoades

Penn State Behrend, USA

Alicyn Rhoades’s webpage

Leire Sangroniz

University of Minnesota, USA

Leire Sangroniz’s webpage

Melt memory of semicrystalline polymers

Birgit Strodel

Heinrich Heine University Düsseldorf, Germany

Birgit Strodel’s webpage

Effects of in vivo conditions on protein aggregation:computational approaches

The aggregation of proteins into β-sheet structures has been extensively studied in vitro underconditions that are far from the physiological ones. There is need to extend these investigationsto in vivo conditions where protein aggregation is affected by a myriad of biochemical interac-tions. As a hallmark of numerous diseases, these self-assembly processes need to be under-stood in detail to develop novel therapeutic interventions. The aim of our work is to elucidate theeffects of various in vivo components and conditions, such as the presence of metal ions, oxida-tive stress, an acidic environment mimicking tissue inflammation, the presence of cell mem-branes and the brain extracellular matrix on the conformational dynamics and aggregation of theAlzheimer’s disease-related amyloid-β peptide. To this end, we develop multiscale simulationapproaches, perform large-scale molecular dynamics simulations, and establish novel analysistools allowing us to unravel the aggregation pathways under varying external conditions. Themost recent and enlightening results from these simulations will be presented in my talk.

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