Contemporary attempts to study defects in soft matter rely mainly on optical (e.g., widefield microscopy, fluorescence microscopy, etc.) or electron and X-ray imaging techniques. These methods mainly focus on structural imaging and defect localization rather than their dynamic processes such as migration or transformation of soft matter defects.

An entirely new technique is required for studying defect dynamics, which would enable sufficiently fast detection of ultra-low electrical currents with high resolution, down to the level of single defects. The main goal of our project is the real-time investigation of nanoscale dynamic processes inside single self-assembling peptide nanofibers and their formation mechanisms using nanodiamonds with color centers.This project aims to answer fundamental questions related to nanofiber and nanogel formation.

Doping systems of small molecules and polymers with additives has been shown to be a highly efficient method for varying the charge carrier density over multiple orders of magnitude. While the implications on the charge but also thermal transport within these materials systems are currently being studied extensively, the impact on the hybridization at the interface between the molecules and metallic layers and spin transport mechanisms within the organic semiconductors (OSCs) remains to be unveiled. Recently, hybrid molecule/magnet interfaces have gained significant interest in the field of spintronics. The precise control of structure via synthesis and tunability of electronic properties by structural design make molecules a compelling materials system for systematic studies with unprecedented control of structural and electronic properties. The aim of this project is to utilize the tunability of molecular systems to systematically study spintronic phenomena in hybrid magnetic metal/ OSC devices.

A disadvantage of using organic semiconductors for displays and lighting is their relatively broad emission spectrum due to inhomogeneous broadening. The emission spectrum can be considerably narrowed by blending a blue-emitting organic host with a green or red-emitting dye or sensitizer with narrow linewidth. In polymer-based LEDs (PLEDs) it has been demonstrated that due to efficient energy transfer from the host to the sensitizer already for 1% sensitizer concentration 95% of the blue excitons are transferred to a red dye.^[1] For efficient energy transfer the absorption spectrum of the sensitizer has to overlap with the emission spectrum of the host, such that by definition sensitizers have a smaller bandgap as compared to the host. With regard to charge transport these sensitizers will therefore act as defects that will severely trap charge carriers.

[1] Virgili, T.; Lidzey, D. G.; Bradley, D. D. C. Efficient Energy Transfer from Blue to Red in Tetraphenylporphyrin‐Doped Poly (9, 9‐dioctylfluorene) Light‐Emitting Diodes. Adv. Mater. 2000, 12, 58-62.

The generation of molecular hydrogen with visible light typically relies on multi-component systems and the absorption of two photons per catalytic turnover. Single-molecule photocatalysts are highly desirable, but they suffer from very low hydrogen evolution rates. Based on our prior work on two-photon mechanisms for efficient photoreductions in water [1–4], we aim to explore novel hydrogen generation pathways via single-molecule catalysts (and inexpensive sacrificial electron donors) with the hydrogen atom as key species. The latter will be produced through direct proton reduction by hydrated electrons [2,4,5] or via an essentially unexplored proton-coupled electron transfer to the solvent.

[1] Pfund, B.; Steffen, D. M.; Schreier, M. R.; Bertrams, M.-S.; Ye, C.; Börjesson, K.; Wenger, O. S.; Kerzig, C. UV Light Generation and Challenging Photoreactions Enabled by Upconversion in Water. J. Am.
Chem. Soc. 2020, 142 (23), 10468–10476. https://doi.org/10.1021/jacs.0c02835.

[2] Kerzig, C.; Guo, X.; Wenger, O. S. Unexpected Hydrated Electron Source for Preparative Visible-Light Driven Photoredox Catalysis. J. Am. Chem. Soc. 2019, 141 (5), 2122–2127. https://doi.org/10.1021/jacs.8b12223.

[3] Kerzig, C.; Wenger, O. S. Sensitized Triplet–Triplet Annihilation Upconversion in Water and Its Application to Photochemical Transformations. Chem. Sci. 2018, 9 (32), 6670–6678.
https://doi.org/10.1039/C8SC01829D.

[4] Kerzig, C.; Goez, M. Combining Energy and Electron Transfer in a Supramolecular Environment for the “Green” Generation and Utilization of Hydrated Electrons through Photoredox Catalysis. Chem.Sci. 2016, 7 (6), 3862–3868. https://doi.org/10.1039/C5SC04800A.

[5] Kerzig, C.; Wenger, O. S. Reactivity Control of a Photocatalytic System by Changing the Light Intensity. Chem. Sci. 2019, 10 (48), 11023–11029. https://doi.org/10.1039/C9SC04584H.

Supramolecular materials that are composed of small building blocks interacting through non-covalent interactions offer promising applications in various fields.^1-2 The dynamic nature of supramolecular polymers, which contributes to their highly desirable adaptive and responsive behavior, is believed to stem from defects in the monomer packing. Defect engineering is a well-established strategy in hard materials to control properties and achieve emergent characteristics. While extensive research has focused on achieving precise structures in supramolecular polymers,^3-6 the potential of incorporating defects in the realm of supramolecular polymers has been unexplored.

This project addresses a central question in SFB1552, namely: Are there intrinsic defects present in supramolecular polymers? How can we identify defects? Are these defects static or dynamic? How can defects be engineered in supramolecular polymers? It will not only give insight into fundamental aspects of defect and defect engineering in supramolecular polymers but will also provide tools to create new supramolecular materials.

[1] Temporally Controlled Supramolecular Polymerization, Dhiman, S. J. George, Bull. Chem. Soc. of Jpn., 2018, 91, 687-699. https://doi.org/10.1246/bcsj.20170433

[2] ATP‐Driven Synthetic Supramolecular Assemblies: From ATP as a Template to Fuel, A. Mishra,^ǂ Dhiman,^ǂ S. J. George, Angew. Chem. Int. Ed., 2021, 60, 2740-2756. https://doi.org/10.1002/anie.202006614

[3] Adenosine-Phosphate-Fueled, Temporally Programmed Supramolecular Polymers with Multiple Transient States, S. Dhiman, A. Jain, M. Kumar, S. J. George, Am. Chem. Soc., 2017, 139, 16568-16575. https://doi.org/10.1002/anie.202006614

[4] Transient Helicity: Fuel‐Driven Temporal Control over Conformational Switching in a Supramolecular Polymer, Dhiman, A. Jain, S. J. George, Angew. Chem. Int. Ed., 2017, 56, 1329-1333. https://doi.org/10.1002/anie.201610946

[5] Chemical fuel-driven living and transient supramolecular polymerization, A. Jain, S. Dhiman, A. Dhayani, P. K. Vemula, S. J. George, Commun., 2019, 10, 450. https://doi.org/10.1038/s41467-019-08308-9

[6] Redox-Mediated, Transient Supramolecular Charge-Transfer Gel and Ink, Dhiman, K. Jalani, S. J. George, ACS Appl. Mater. Interfaces, 2020, 12, 5259-5264. https://doi.org/10.1021/acsami.9b17481

Supramolecular polymer networks consist of mono-, oligo-, or polymeric building blocks that are linked by transient, non-covalent bonds. In this project, we intend  to derive a conceptual mechanism for the defect-assisted building block migration in transient model networks that allows for quantitative predictions of their relaxation on micro- and macroscopic time and length scales. For this purpose, we will further develop our model-network platform to hetero-complementary precursor-polymer interconnection to obtain truly model-type defect-free networks as a reference state, and then to purposely impart local connectivity flaws and track the motion of the building blocks that cause them. The perspective of that work is to facilitate the design of transient networks with adjustable local penetration properties and restructuring capabilities.

Multidomain peptide materials combine the structural precision of natural oligopeptide sequences with the scalability of synthetic polymers. They serve as modular building blocks for supramolecular polymerization in water, in order to prepare synthetic mimics of extracellular matrices, cytoskeletal mimics or silk-like biomaterials. Here, our aim is to develop segmented oligopeptide motifs that allow control over the ratio of intra- to inter-particle folding and therefore the branching (the defect) in 1D supramolecular polymers.

In consequence, the rational design of the peptide subunits, hydrophilic polymer length allows to modulate the kinetics of supramolecular polymerization, uptake of the defect sites and ultimately tune the assembly protocol for the multicomponent hierarchal structures. Compared to covalent hydrogels, dynamic supramolecular networks remain poorly understood. The application of multicomponent supramolecular polymers enables the design of molecular defects and investigate their role in network formation.

In this project, we want to make the first step towards the design of control mechanisms to realize homeostatic self-regulating behavior into self-assembling systems and first materials so as to be able to engineer resilience against defects. To this end, we will design dormant self-regulatory mechanisms in material systems that become activated by an external trigger, whereby the external trigger changes a system/destroys a function, and the dormant self-regulation mechanisms allow for a return to the initial system. We focus on precise chemical defects and precise chemical self-regulation mechanisms, applied to systems based on peptide self-assemblies, polymer hydrogels, and DNA-based systems. Our external triggers will focus exclusively on light-based photo-oxidative and photo-reductive triggers enabling the release of chemicals that act on the system (photo-redox agents, photo-protected reducing agents). Our internal control systems will be based on counteracting dormant redox systems and enzymatic reaction networks that can counterbalance and repair these defects.

Proteins are solvated by water molecules which form water shells around the protein surface. Still water molecules can also penetrate protein cavities such as the binding pocket and are then termed “bound water”. Such bound water molecules can form networks built up by several bound water molecules. The binding of a ligand to a protein cavity or the chemical modification (including post-translational modification) of a protein or its ligands can either displace an individual bound water molecule or the entire network: we regard such a displacement as “defect” of soft matter.

In our project we will combine experimental physical chemistry, machine-learning approaches and full-atomistic and implicit solvent computer simulations to understand how defects in the water networks in protein cavities are driven by small molecules with the long-term aim of engineering these defects specifically. We will study well-characterized protein-ligand systems to design ligands leading to a specific change in the thermodynamic profile. Ultimately, we aim to rationalize design principles for novel ligands to better understand the molecular recognition process and guide the design of novel ligands.

For decades, membrane-forming amphiphiles have proven its importance as building components of versatile carrier and model systems. Even though liposomal carrier systems have been investigated in clinical applications since the 1990s, central questions regarding release mechanisms or the controlling of membrane permeability remain open until today. The permeability of bio membranes is set by additional molecules such as membrane proteins and ionic channels that create “defects” in the membrane. The effects of such defects are not adequately investigated neither for natural lipid membranes of biological origin nor for artificial membranes composed of polymers and surfactants. However, complex mechanisms and phenomena such as local microphase separation and de-mixing,clustering and domain formation are of great importance in controlling the self-assembly process of membranes.

Therefore, this project aims to control the self-assembly process of amphiphiles in the presence of colloidal nanostructures in order to improve the understanding on defect generation and its effects on the integrity and permeability of engineered vesicular membranes.

Topological defects are omnipresent in nanostructured materials made of block copolymers, and can have a critical influence on mechanical or transport properties of the materials. The goal of this project is to explore and analyse ways to control the structure and distribution of such defects by numerical simulations on different scales. Specifically, we will investigate the effect of blending in small fractions of dopant molecules such as star copolymers, or dopant particles such as polymer-grafted colloids, which are designed such that they might promote defect formation and/or stabilize defects.

In this project we aim to break new ground in the fundamental design and in conceptual approaches for understanding and predicting ATP-driven DNA-based reaction networks using dynamic ligation/restriction networks orchestrated through T4Ligase and restriction enzymes. As a particular challenge, we will set out to integrate structural point defects into the sticky ends of our DNA tiles, which not only influence the kinetics (e.g. of ligation), but which also gives rise to autonomous reconfiguration of the structures.

To address this challenge, we forge a team between Walther (chemistry, DNA nanoscience, systems chemistry) with Gerber (biology/medicine, systems biology, bioinformatics and machine learning) to address both experimental challenges and mathematical modelling.

At first glance, biological membranes that constitute cytoplasmic membranes and separate organelles from the surrounding cytoplasm, seem to be simple and passive barriers. A closer look reveals that membranes are composed of a plethora of different lipid species and contain integral or peripherally attached proteins. Although mixtures of the basic membrane building blocks, the membrane lipids (mainly phospholipids), predominantly form a disordered two-dimensional liquid, complex phenomena such as ordering, local lipid de-mixing, lipid domain formation, and formation of non-canonical membrane structures can occur.

In this project, we will investigate the “behavior” of a membrane in the vicinity of a membrane defect, which has been generated using different triggers. Membrane defects will be introduced in a controlled way using i) small molecules, ii) lipid modifying enzymes and iii) membrane-binding proteins. Furthermore, (iv) we will develop novel photoswitchable phospholipid systems that can be incorporated into model membranes.

Active matter systems are driven out of equilibrium by a local influx and dissipation of energy, in many cases leading to self-propelled particle motion. The collective dynamics of active matter systems is characterized by a variety of notable phenomena that are impossible in equilibrium thermodynamics.  In recent years, it has been found that topological defects occurring in active matter are very useful for characterizing these collective phenomena, and in particular also for controlling them. This has been widely studied in the physics of active nematics, but much less in systems of particles with self-propelled constituents. In this project, we plan to study the emergence and dynamics of topological defects in systems of ellipsoidal active particles moving orthogonal to their symmetry axis.

The idea of this project is that, as part of the SFB, we have a multidisciplinary expert team in the area of sensing and spectroscopy. The team’s expertise includes, as a major constituent, quantum sensing based on color centers in diamond, but it goes significantly beyond that, extending to areas like ultrafast nonlinear optical spectroscopy and ultrasensitive atomic magnetometry, among others.In the course of the preliminary work on the SFB proposal, we have identified a number of specific characterization challenges across the range of SFB subprojects that the Q01 expert team will help address in close collaboration with the individual subproject teams.

Standard tools to study defects in soft matters systems are based on optical methods (e.g., fluorescence microscopy and spectroscopy (1), dynamic light scattering), electron microscopy, and X-ray imaging techniques. However, the spatial resolution of conventional optical microscopy, one of the most widely used tools, is diffraction-limited to, at best, 200 nm laterally and 600 nm axially in the visible range and thus restricts the visualization of the small size of single soft matter defects, typically in the range of ~1 nm.

In this proposed project, we intend to develop and investigate new correlative optical microscopy and spectroscopy methods with the aims to 1) image soft matter systems with improved (sub-20 nm) imaging resolution across a wide range of different environments (e.g., aqueous solution at different pH values, organic solvents, air), and 2) determine the orientation of molecules at improved imaging speed (within ~100 ms) and resolution up to single-molecule level while excluding spontaneous fluorescence effects.

This cross-sectional Q-project will investigate static and dynamical properties of different polymer networks using X-ray photon correlation spectroscopy (XPCS). Combined with other techniques such as Neutron spin echo or dynamic light scattering this will provide us comprehensive information on the defect-induced network dynamics over many time- and length scales.

As an experimental cross-link project, we will further support all projects in terms of X-ray scattering techniques. This is, we intend to use both our in-house facilities at MPI-P (Powder diffraction and small angle X-ray scattering) as well as large scale facilities such as storage rings and X-ray free electron lasers (XFEL).