Research Field I

Synthetic polymer science and click-chemistry

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.

Reproduced from the reference31 by permission of The Royal Society of Chemistry.
Modified with permission from the reference24. Copyright 2015©, WILEY-VCH Verlag GmbH & Co.  KGaA, Weinheim.

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.

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,14nearly 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.

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.

References

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