Stefan Mommer

Last Name

Mommer

First Name

Stefan

ORCID

0000-0003-1400-5681

Organisational unit

09472 - Tibbitt, Mark / Tibbitt, Mark

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Publications 1 - 5 of 5

Photoresponsive Slide-Ring Gels Enable Modulation of Sliding Dynamics
Cafagno, Dalila; Silvi, Serena; Tibbitt, Mark W.; et al. (2025)
Angewandte Chemie. International Edition
Cyclodextrin-based slide-ring gels (SRGs) have emerged as a promising class of materials owing to their unique topology. Upon mechanical loading, the slidable cross-links of the polymer network freely translocate along the polymer backbone enabling pronounced energy dissipation in the material, which is associated with exceptional ductility and toughness. Despite the critical role of sliding dynamics in defining SRG mechanical properties, attempts to control them have primarily been limited to tuning the overall loading of macrocycles. Further, SRGs that can be triggered via an external stimulus have yet to be reported. In this work, we present light-responsive SRGs based on azobenzene-containing polymers. Reversible photoswitching of the azobenzenes modulates the sliding dynamics of the threaded α-cyclodextrin (α-CD) macrocycles. By using UV–Vis and circular dichroism spectroscopy, we show that α-CDs readily bind to the azobenzenes along the polymer backbone in the E configuration. Upon light irradiation, and thus isomerization to the Z isomer, the macrocycles no longer interact with the azobenzenes, allowing them to freely translocate along the polymer backbone. As a result of this E to Z isomerization and difference in sliding dynamics, the mechanical properties of the SRGs reversibly alternate between a stiff and a soft state.
γ-Functional Iminiumthiolactones for the Single and Double Modification of Peptides
Mommer, Stefan; Warner, Nina; Lienert, Caroline (2023)
Bioconjugate Chemistry
Thiolactones (TL) can be readily incorporated into polymeric materials and have been extensively used as a ligation strategy despite their limited reactivity toward amine-containing substrates. Comparatively, iminiumthiolactones (ITL) are much more reactive, yet to this day, only the nonsubstituted ITL known as Traut’s reagent is commercially available and used. In this work, we advance current TL/ITL chemistry by introducing reactive side groups to the ITL heterocycle in the γ-position, which can be orthogonally modified without affecting the ITL heterocycle itself. To study the reactivity of γ-functional ITLs, we subject one of our derivatives (γ-allyl-functional ITL 3b) to model reactions with several peptides and a chosen protein (lysozyme C). Using mild reaction conditions, we successfully demonstrate that the γ-functional ITL exhibits orthogonal and enhanced reactivity in a single or double modification while introducing a new functional handle to the biological substrate. We believe that γ-functional ITLs will advance the original Traut chemistry and open promising opportunities for the bioconjugation of biological building blocks to existing functional molecules, polymers, and materials.
Photoswitchable Bis(amidopyrroles): Modulating Anion Transport Activity Independent of Binding Affinity
Villarón, David; Bos, Jasper E.; Kohl, Fabien; et al. (2023)
The Journal of Organic Chemistry
Toward photocontrolof anion transport across the bilayermembrane,stiff-stilbene, which has dimethyl substituents in the five-memberedrings, is functionalized with amidopyrrole units. UV-vis and H-1 NMR studies show high photostability and photoconversionyields. Where the photoaddressable (E)- and (Z)-isomers exhibit comparable binding affinities, as determinedby H-1 NMR titrations, fluorescence-based transport assaysreveal significantly higher transport activity for the (Z)-isomers. Changing the binding affinity is thus not a necessityfor modulating transport. Additionally, transport can be triggered in situ by light.
Tough Hydrogels for Load-Bearing Applications
Petelinšek, Nika; Mommer, Stefan (2024)
Advanced Science
Tough hydrogels have emerged as a promising class of materials to target load-bearing applications, where the material has to resist multiple cycles of extreme mechanical impact. A variety of chemical interactions and network architectures are used to enhance the mechanical properties and fracture mechanics of hydrogels making them stiffer and tougher. In recent years, the mechanical properties of tough, high-performance hydrogels have been benchmarked, however, this is often incomplete as important variables like water content are largely ignored. In this review, the aim is to clarify the reported mechanical properties of state-of-the-art tough hydrogels by providing a comprehensive library of fracture and mechanical property data. First, common methods for mechanical characterization of such high-performance hydrogels are introduced. Then, various modes of energy dissipation to obtain tough hydrogels are discussed and used to categorize the individual datasets helping to asses the material's (fracture) mechanical properties. Finally, current applications are considered, tough high-performance hydrogels are compared with existing materials, and promising future opportunities are discussed.
Ultrahigh-Molecular-Weight Polymer Gels in Aqueous Media Using Cucurbit[8]uril-Assisted Radical Polymerization
Ansart, Elise; Hosch, Rebekka; Tibbitt, Mark W.; et al. (2025)
Macromolecules
Ultrahigh-molecular-weight (UHMW) polymer materials show enhanced material properties due to entanglements and reduced polymer dynamics that occur at extreme degrees of polymerization. While various living controlled polymerizations have been explored for the synthesis of UHMW polymers, free-radical polymerization (FRP) remains limited for this application, given low initiation efficiencies and poor reproducibility. In this work, we exploit host–guest interactions between Cucurbit[8]uril and the thermoinitiator VA-044 to down-regulate the number of active radicals during the radical polymerization of acrylamide (AAm). This approach produces UHMW polymers (up to 5.5 MDa) that form hydrogels in situ. We investigate various reaction parameters (e.g., the concentration of CB[8] and ratio of CB[8] to VA-044) and apply this strategy to other water-soluble monomers. Additionally, detailed rheological analyses of the materials show how upon exceeding a molecular weight of Mn = 3 MDa, the stiffness of the hydrogels increases and becomes frequency-independent. Due to the simplicity of this method, UHMW polymers and hydrogels in aqueous media can be easily accessed by using minimal amounts of the CB[8] macrocycle as an additive to an otherwise standard FRP procedure.

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Stefan Mommer

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