Martin-Luther-Universität Halle-Wittenberg

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We strive to generate and apply polymer materials, both via synthetic and biological methodologies, equipped with both, dynamic and adaptive properties. Focus areas are the molecular design of functional polymers (synthesis, novel functionalization strategies) via control of inter/intramolecular interactions. Our generated materials address self-healing polymers, biomimetic diagnostic/delivery systems (artificial membranes, protein/polymer conjugates) and concepts for charge-storage-materials (ionic liquids, batteries, fuel cell membranes).

Research fields with selected recent publications

  • Generate biomimetic, renewable and self-healing polymers1-3 (research area II)
  • Synthesis and novel analytical methods for the preparation of complex macromolecular architectures4-8 (research area I)
  • Design of nanoscaled medical imaging systems and drug-delivery systems9-11 (research area V)
  • Develop novel electrolytes for battery and transistor systems7, 12 (research area IV)
  • Transfer self-healing concepts into thermoplastic materials, elastomers and electrode-materials3, 13-17 (research area II)
  • Study biological folding, aggregation- and chirality transfer-principles4, 18-20 (research area III)
  • 3D-printing of polymers21 (research area V)
Research Areas Overview

Research Areas Overview

Research Areas Overview

Develop novel electrolytes for battery and transistor systems

Transfer self-healing concepts into thermoplastic materials, elastomers and electrode-materials
Nanopatterning
Block copolymers
Supramolecular polymers
Nanoparticles
Charge-storage materials
Design of nanoscaled medical imaging systems and drug-delivery systems

Study biological folding, aggregation- and chirality transfer-principles
Nanoporosity
Catalysis
Biomaterials
Biomembranes
Synthesis and novel analytical methods for the preparation of complex macromolecular architecturesLiving radical polymerization (ATRP, NMP, RAFT)
Living cationic polymerization
ROMP, ADMET, ROP
Polycondensation methods
Resin Materials
Generate biomimetic, renewable and self-healing polymersNanocomposites/Nanofillers
Resin materials
Self healing materials, Vitrimers
Polymer technology
3D-printing of polymers
Polymer analyticsNMR-Analysis (1D-, 2D)
Mass spectrometry (MALDI, ESI-TOF)
Hyphenated Techniques (SEC-MALDI, ESI-TOF)
Chromatography (LC, SEC)
Surface analysis

Macromolecules are key molecules, indispensable for modern society. They are not only present as widely known structural materials in eg. automobiles or aeroplanes, but are found in biomedicine, modern energy- or information technology22. Research focus in our group is the preparation of functional polymers and their application in modern technology, designing polymers for medicine, as advanced structural materials, or for novel batteries and transistors. Based on the polymer’s structural complexity we use all known living polymerization (such as ATPR, RAFT, NMP, ROMP, LCCP, LAP and ROP-methodologies)23-25 and modern functionalization strategies known from synthetic organic chemistry, including "click"-based methods26-31. Novel polymeric architectures (functional graft-, cyclic-, star-polymers)32-34 and the site-specific integration of supramolecular interactions (such as hydrogen bonds, ionomers, mechanophores)35-39 into tailored macromolecules allow to generate advanced materials in the areas of biomedicine40-44, modern imaging technology, batteries45, transistors or self-healing-features40, 46-50. Using modern high resolution mass spectrometry (LC/ESI-MS and GPC/LC-MALDI-methods) and complex hyphenated technologies (two-dimensional chromatography (2D-LC/GPC)), advanced functions of macromolecules can be integrated by use of 3D-printing technologies.

For details see one of our review papers22, 26-30, 32-37, 40-44, 46-49, 51-58 and books-sections15, 23-25, 45, 51-52, 59-64.

Literature Research Overview
Literature_Research_Overview.pdf (172 KB)  vom 18.06.2020

Synthetic polymer science and click-chemistry
(Research focus I)

Modified from the reference54 with permission. Copyright 2019©, American Chemical Society.

Modified from the reference54 with permission. Copyright 2019©, American Chemical Society.

Modified from the reference54 with permission. Copyright 2019©, American Chemical Society.

One traditional focus of our research group is directed to novel polymers, novel monomers and novel synthetic methodologies. Principles of organic synthesis, macromolecular chemistry and catalyst-design are addressed, aiming to precisely engineer a macromolecules’ chemical identity.1-8 To this endeavor precise chain length, low polydispersities, and the desired composition and arrangement of monomers are embedded into the desired architecture. Therefore a major focus is directed on living polymerization methods, where significant effort is placed on living carbocationic polymerization (LCCP), RAFT-polymerization, nitroxide mediated polymerization (NMP), living ring-opening polymerization (ROP), ring-opening metathesis polymerization (ROMP) and anionic polymerization (LAP). Besides endgroup- and side-chain modifications of synthetic polymers and proteins, effort has been placed for “click”-based methodologies in polymer science.

CuAAc Principles

CuAAc Principles

CuAAc Principles

Being among the first ever in 20049 to apply CuAAc (copper catalyzed “click”-chemistry) in combination with living polymerization (see our first landmark paper in this field) we have developed and used CuAAc extensively during the past decades (see our selected reviews from 20076, 20085 and 20193 as examples). Based on its extremely high functional group tolerance, its robustness due to autoacceleration-effects10-11 and chelation-assistance,12 CuAAc is currently the only truly useful click-chemistry in Barry Sharpless definition, widely applied in polymer science. It is this knowledge which ensures fast, efficient, and also reliable transformations before, during and even after polymerization. Novel developments of our research group deal with the “thio-bromo-click”-chemistry”13-15, being advantageous if biomolecules and the conjugation of polymers onto biomolecules is desired15. Significant effort is spent to generate biohybrid-molecules, where polymer science and proteins/peptides meet, may it be as polymer-peptide-conjugates14-15, as polymer-protein-conjugates16-17, or as artificial beta-turn-mimetics18-20

Reproduced from the reference58 with permission. Copyright 2012©, American Chemical Society.

Reproduced from the reference58 with permission. Copyright 2012©, American Chemical Society.

Reproduced from the reference58 with permission. Copyright 2012©, American Chemical Society.

The synthesis of complex supramolecular architectures, able to assemble via hydrogen bonds is a longlasting topic in our group. Based on early work, where end-group-modified polymers were synthesized via LCCP-chemistry21-23, the approaching RAFT-, ROP-, ADMET, and ROMP-polymerization-methods have allowed to prepare highly complex polymer architectures. It must be mentioned that now, in combination with CuAAC and “thiobromo-click”-chemistry,14 nearly any functional group can be connected onto a desired polymer backbone. Recent examples are related to combinations of RAFT-polymerization bearing complex hydrogen bonds24-31 and ionomers32-33, ROMP-8-9, 34-41, combinations of ROP (N-carboxyanhydrides, 1,3-oxazolines, caprolactones/caprolactames)19, 42-48 with/without ADMET43, 49-53, NMP10, 54-56. Only the proper combination of high-resolution mass spectrometry (ESI/MALDI-TOF), often combined with liquid chromatography is then able to proof purity of these samples and resolve their precise structure. Coupled and hyphenated techniques have been developed to this endeavor in our group (ESI/MALDI-TOF – 2D-chromatrography)57-58 to achieve information on complex architecture and substitution patterns or crossover-chemistries59-60.

living carbocationic polymerization

living carbocationic polymerization

living carbocationic polymerization

There has been - and still is - a longlasting tradition in living carbocationic polymerization (LCCP) in our research-group, where polyisobutylene (PIB) is prepared by living carbocationic polymerization (LCCP). PIB is one of the few and only polymers only addressable by cationic polymerization. Being one of the few truly biocompatible polymers, defined architectures of PIB-polymers (linear-21-23, block-61, star-,12, 61-63 endgroup-functionalized64-65, sidegroup-functionalized66, hyperbranched-,67 cyclic68, grafting-from-SiO269) are addressed in our group via LCCP, used for subsequent (biomimetic) materials18, 70-75, self-healing elastomers25, 65, 76-77and  ionic liquids78-79. We are further developing novel PIB-polymers for advanced applications in biomedicine and technology, as biocompatible polymers, surfaces, and as self-healing materials.

Literature Research Area I
References_Resarch_AreaI.pdf (182,5 KB)  vom 18.06.2020

Biomimetic, renewable and self-healing polymers
(Research focus II)

Modified with permission from the references.7,8,61 Copyright ©2013, John Wiley and Sons and Copyright 2018©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Modified with permission from the references.7,8,61 Copyright ©2013, John Wiley and Sons and Copyright 2018©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Modified with permission from the references.7,8,61 Copyright ©2013, John Wiley and Sons and Copyright 2018©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Reuse and life-cycle-enhancement of polymers is among the most pressing societal needs. We address novel concepts for reusing thermoplastics and thermosets based on vitrimers1, self-healing materials2 and reusable rubbers, funded by the graduate school AGRIPOLY, DFG- and EU-projects. Both, chemical synthesis and enzymatic degradation are studied to generate polymers with improved life-cycle as modern, environmentally friendly materials3.

Modified with permission from the references.2,7 Copyright ©2013, John Wiley and Sons and Copyright 2018©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Modified with permission from the references.2,7 Copyright ©2013, John Wiley and Sons and Copyright 2018©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Modified with permission from the references.2,7 Copyright ©2013, John Wiley and Sons and Copyright 2018©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Self-healing is among the great desires in materials, especially if accomplished autonomous and at room temperature conditions – only then an application in everyday life, such as coatings, smartphones, electronics is possible. One focus is placed on the embedding of multiple hydrogen-bonds,4-6 able to introduce self-healing into any desired polymeric materials.2, 7-9 Based on our longstanding tradition in hydrogen-bonds,6 their assembly, their phase-behavior10 and strength in polymers,4, 11-13 we are able to adapt the required strength and properties for the effect needed.7, 14 Proper choice of the hydrogen bond6, 15-17 in relation to the polymer allows to tune the healing-response, the healing time, and the healing conditions.18-19

Reproduced with permission from the reference.11 Copyright 2017©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reproduced with permission from the reference.11 Copyright 2017©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reproduced with permission from the reference.11 Copyright 2017©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multiple-H-bonds based on barbiturates and complex, chelate-type H-bonds13, 20 in particular are prone to reversible assembly, useful for room-temperature self-healing.18, 21-22 Different methodologies of synthetic (polymer) chemistry are used to address the incorporation of the H-bonds into the final polymers, such as RAFT, ATRP, NMP, living carbocationic polymerization (LCCP), or living anionic polymerization (LCP). Thermoplastic, elastomeric and also thermoset/composite-materials18, 21-25 are equipped with self-healing properties, the latter using dynamic disulfide-bonds, introducing vitrimeric properties26. We can achieve self-healing at ambient conditions, technologically important when transferred to structural materials and coatings.24-25, 27 Since in all cases the intrinsic dynamics of the hydrogen bond is important and often different from the solvated state,28 their dynamics4 within the solid material are studied via various physical methodologies, among them melt-rheology,29-31 X-ray scattering,19, 32-33 or solid state NMR-spectroscopy11 to reveal mechanistic details of such self-healing processes.29

Reproduced with permission from the reference.34 Copyright 2017©, American Chemical Society.

Reproduced with permission from the reference.34 Copyright 2017©, American Chemical Society.

Reproduced with permission from the reference.34 Copyright 2017©, American Chemical Society.

Our second approach uses encapsulation methods, coupled to a triggered “click”-chemistry to sense and subsequently heal the material.34 Based on the enormous versatility of the CuAAc (copper-catalyzed-click-reaction)34-37 as developed by Meldal in 2001  and its extreme robustness mainly due to autoacceleration-effects38-39 and chelation-assistance,40 this chemistry can easily be used in stress-induced, catalytic systems. We still work on the improvement of this highly valued self-healing materials using modern multicomponent 3D-printing-technologies.

Modified with permission from the reference.43 Copyright 2016©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modified with permission from the reference.43 Copyright 2016©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modified with permission from the reference.43 Copyright 2016©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Embedding nanosized capsules into the polymers, wherein reactive components are stored, a stress-triggered signal releases the components and activates the catalyst.41-42 Various self-healing nanocomposites and thermoset-systems, able to heal cracks at ambient temperature within several minutes have been developed.39, 41-46 Graphene-47 and CNT-based Cu-catalyst48-50 are specifically attractive for this purpose due to their high stability and excellent dispersibility. With specially designed bis-N-heterocyclic Cu(I)-complexes as mechanophores a direct activation by stress can be achieved,51-54 allowing to sense and quantify stress inside thermoplastic- and thermoset polymers and biomaterials such as elastin-like peptides.55-56

Current research activities in this area are using 3D-printed multicomponent materials57 to embed all types of self-healing and self-sensing properties58-59 in coatings, elastomers, biomaterials, together with the exact quantification of the molecular force required to activate the mechanophores60-61 via SFMS-methods.

References_Research_AreaII
References_Resarch_AreaII.pdf (166,9 KB)  vom 18.06.2020

Study biological folding-, assembly and chirality transfer-principles (Research focus III)

amyloid-proteins

amyloid-proteins

amyloid-proteins

Secondary-structure of proteins and peptides is crucial for their function in living systems, in its undesired assembly being responsible for e. g. Alzheimer’s or Parkinsons’ disease.1 Within the DFG-funded collaborative research project SFB TRR 102 two projects deal with amyloid-proteins to understand and prevent disease-relevant aggregation via synthetic polymers, able to fold- and unfold during aggregation. Main aim is to understand, control, and inhibit fibrillation by concepts of polymer-science and a deeper understanding of the fibrillation processes. Concepts of synthetic chemistry are combined with proteins to generate hybrid-systems, able to fold and aggregate similar to the native peptide systems. Both, peptide- and polymer chemistry are researched in this area.

precision-hybrid-polymers

precision-hybrid-polymers

precision-hybrid-polymers

Synthesis via ring-opening (ROP) and ADMET-polymerization generates precision-hybrid-polymers consisting of polyamino-acids and repetitive middle segments displaying a defined flexibility/rigidity2-4. They allow to study refolding and cooperative phenomena, similar to protein folding and amyloid assembly.5-8 Recent activities are directed to understand the influence of distance, endgroups and numbers of the folding elements on the final three-dimensional structure of the assemblies. Photoswitchability,9-11 assembly with embedded constrained folding elements,2-3 and dynamic secondary structure-elements (such as beta-folds, alpha-helices)5, 7 were successfully introduced into the polymer chains, acting as biomimetics for larger proteins5-8. Currently, the concept is extended onto polymer/amyloid-molecules to design, understand and influence the folding and aggregation pathways of new such detrimentally aggregating proteins12-14.

Reproduced with permission from the reference.16 Copyright 2017©, American Chemical Society.

Reproduced with permission from the reference.16 Copyright 2017©, American Chemical Society.

Reproduced with permission from the reference.16 Copyright 2017©, American Chemical Society.

Chirality is among the chemical principles required for life. We generate  molecules with switchable chirality, where the transfer of chirality onto nonchiral side-chains is probed. As probed in helically chiral polymers,15-16 the transfer of only one chiral group can have influence on many tens of monomers, linked into a polymer chain to yield either right- or left-handed helices, induced just by one chiral moiety17. We employ precisely engineered polymers based on achiral polyisocyanides, polyisocyanates and achiral polyaminoacids to study the influence of a singular chiral-element embedded in the polymer chain. It demonstrates that only one single chiral moiety can display large chirality-transfer-effects, also termed chiral amplification, taken place presumptively in the early times of the universe.

Reproduced with permission from the reference.17 Copyright 2020©, American Chemical Society.

Reproduced with permission from the reference.17 Copyright 2020©, American Chemical Society.

Reproduced with permission from the reference.17 Copyright 2020©, American Chemical Society.

References_Research_AreaIII
References_Resarch_AreaIII.pdf (142,8 KB)  vom 18.06.2020

Novel electrolyte-polymers for battery and transistor systems (Research focus IV)

Self Healing

Self Healing

Self Healing

Improved charge-transport and the compensation of volume-changes is crucial in technology of modern batteries, fuel-cells and transistors. Several EU/DFG-funded projects (Bat4ever within Horizon-2020, DFG) do address the chemical synthesis of novel ionomers and ionogels, used as electrolytes within large international consortia. Novel long living batteries and transistors with self-healing functions are prepared and studied as future technologies. Novel polymeric ionic liquids1-8 are studied aiming to increase ionic conductivity,1-2 charge-transfer to the electrodes and enable a longer lifetime of the final batteries. Knowledge of ionic mobilities is transferred to interfacial transport processes such as ionic liquid gating,9-10 where the underlying interface and its structural changes are studied.

Reproduced with permission from the reference.9 Copyright 2018©, American Chemical Society.

Reproduced with permission from the reference.9 Copyright 2018©, American Chemical Society.

Reproduced with permission from the reference.9 Copyright 2018©, American Chemical Society.

References_Research_AreaIV
References_Resarch_AreaIV.pdf (111,5 KB)  vom 18.06.2020

Drug-Delivery, Bio-Imaging and 3D-printing of materials (Research focus V)

Reproduced with permission from the reference.2 Copyright 2019©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reproduced with permission from the reference.2 Copyright 2019©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reproduced with permission from the reference.2 Copyright 2019©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The development on novel materials is directed to on novel battery-electrodes, drug-release systems, stress-sensing-1 and (bio)-degradable soft/hard interfaces. Three dimensional (3D)-printing technology has become societies leading method to form materials for many applications. Prominent examples are the 3D- printing of self-healing polymer systems, pharmaceutical delivery materials and capsule-based multicomponent materials. Printing biodegradable polymers, capsules and materials for triggered time-release with defined long term delivery profiles represents an important challenge, currently addressed by proper design and synthesis of 3D-printable (co)-polyesters. We use multimode 3D-printing methods to prepare modern materials, with embedded self-healing-, mechanochromic- and pharmaceutical function.2

Reproduced with permission from the reference.3 Copyright 2015©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reproduced with permission from the reference.3 Copyright 2015©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reproduced with permission from the reference.3 Copyright 2015©, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Delivery of pharmaceutical cargo as nanosized particles, vesicles or aggregates has become a prominent and medical useful endeavor.3-4 Polymers and lipids, equipped with modern STEALTH-technology are particularly interesting in this context, termed vesicles or polymersomes.5-13 Especially in view of site-specific delivery and imaging technology small, STEALTH-like particles with embedded functionalities are important, mediating both, biocompatibility and delivery of drugs, dyes and recognition sites. Based on our longstanding experience on artificial and biological membranes,3-4, 9, 14 we are currently developing ultra-small nanoparticles for high resolution imaging technology. Polymeric carrier-molecules consisting of a single chain are used in photoacoustic spectroscopy, displaying prolonged circulation times and excellent imaging properties.

References_Research_AreaV
References_Resarch_AreaV.pdf (114,9 KB)  vom 18.06.2020

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