Over the past decades, hydrogels and microgels have attracted increasing interest due to their wide range of applications, spanning from biomedical sciences to agriculture. Both hydrogels and microgels are crosslinked polymer networks; however, while hydrogels form macroscopic gel-like structures swollen with water, microgels exist as discrete colloidal particles dispersed in a solvent. Their highly tunable structures make them promising candidates for various functional applications.
Depending on the desired properties, hydrogels and microgels can be either chemically or physically crosslinked, where permanent bonds ensure stability, while transient supramolecular bonds enable reversibility. In this context, we developed a supramolecular cross-linker based on terpyridine-metal complexes, which can be incorporated into stimuli-responsive hydrogels and microgels through a one-pot synthesis in water.
This supramolecular crosslinker endows both hydrogels and microgels with remarkable responsive properties, including a polyelectrolyte effect, alongside temperature responsiveness in thermoresponsive PNIPAM-based systems. Moreover, the crosslinking points are cleavable by oxidation, allowing controlled degradation of the polymer networks on demand.
This metallo-supramolecular strategy enables dynamic and reversible interactions, offering precise control over the structural and functional properties of polymer networks under external stimuli.

Solid polymer electrolytes (SPEs) are important in advancing lithium-ion battery technology due to their potential to address safety concerns, enhance mechanical stability, and improve performance. However, challenges such as limited self-healing and recyclability, and poor interfacial adhesion with lithium metal remain significant barriers. Incorporating self-healing and recycling properties into SPEs can extend their lifespan and reduce waste, while strong interfacial adhesion ensures better contact between the electrolyte and lithium metal, improving ionic transport and battery efficiency. For this purpose, we used imine chemistry in combination with metal organic complex as a route to create dynamic and sustainable reversible adhesives, while reinforcing the polymer with lithium salts to enhance ionic conductivity. . We synthesized imine functional polydimethylsiloxane (PDMS) through the reaction of amine terminated PDMS and 2,5-thiopehene dicaborxaldehyde via Schiff base reaction and cross-linked the resulting polymer with different metal salts (Fe, Zn. Ni) in a single pot chemistry approach. The dynamic nature of the metal-ligand and to a minor extent imine bonds enhances adhesiveness, as well as self-healing and recyclability. We demonstrate that nickel complex is the best in terms of properties such as mechanical strength, healing, recycling and ionic conductivity, compared to the polymers with iron and zinc complexes. With excellent healing and recycling properties, along with promising ionic conductivity, these polymers demonstrate strong potential as solid electrolytes for lithium-ion batteries, offering a safer, more durable, and sustainable solution for next-generation energy storage.

Complex coacervates are liquid phases that form in water upon mixing suitable polyelectrolytes of opposite charge, through spontaneous liquid-liquid phase separation (LLPS). They are potentially biocompatible and biodegradable; their properties depend on the ionic strength of the solution (and therefore they are salt-responsive, and can be processed using salt as a plasticiser); and they sequester organic molecules from solution due to increased solubility. Because of this combination of properties, coacervate droplets have found a variety of applications: such as the compartmentalization of active ingredients for food and cosmetics, the preparation of protocells, or the mimicking of membranelles organelles (MLOs), subcellular compartments involved in biological processes.

The use of coacervates for compartmentalization has two main drawbacks. First, their interfacial tension with water is extremely low, making them very prone to coalescence. Second, coacervates are typically structures in thermodynamic equilibrium (or kinetically trapped), which do not show aging, movement, or transient formation, as MLOs or protocells do.

Recent results in my laboratory have shown that weak electric fields (< 3 V/cm) can be used to energize coacervates, resulting on their splitting, emulsification, and controlled coalescence. The conditions for these processes are much milder than those previously reported for both coacervates and other aqueous phases. Furthermore, by introducing redox-sensitive groups into the polyelectrolyte chains, coacervates can be made responsive to electrochemical reactions, leading to their transient formation, movement, and destruction over length scales of up to centimeters.

3D printing of hydrogels usually relies on a combination of fine-tuned material chemistry and polymer chain architecture to produce inks with adequate yield-stress flow, shear-thinning and self-healing behavior. [1] Recently, granular hydrogel inks made of jammed microgels have shown great potential due to their intrinsic yield-stress behavior and highly tunable compositions. [2] To afford their long-term dimensional stability, a curing process that connects the microgels together after printing is necessary, however this process must be accurately and timely controlled. [3]
Herein, a novel approach that combines in a single system the rheological yield-stress behavior of granular hydrogels together with the tunable interactions strength of polyelectrolyte complexes is proposed to develop a 3D printable granular hydrogel ink that exhibits long-term stability and responsive dimension changes in liquid medium without further curing. [4] Hybrid microgels made of hyaluronic acid – chitosan (HAMA-CHIMA) oppositely charged polyelectrolytes were first prepared at a high enough salt concentration to shield the electrostatic interactions. They were subsequently jammed to obtain a granular hydrogel that is 3D printable through extrusion printing. By decreasing the salt concentration of the medium below the critical concentration for electrostatic association between the polyelectrolytes, microgels with decreasing size leading to hydrogels with tunable stiffness, packing density and size were obtained. The 3D printed scaffolds exhibit long-term stability without need of chemical crosslinking and post-printing modulation of the resolution is also rendered possible. This approach opens up the way to the design of more functional 3D hydrogel constructs with dynamic, biocompatible and recyclable properties.

Chemiluminescence is a phenomenon, consisting in the chemical formation of the excited molecule, which returns to its ground state with the emission of the photon. Luminol (3-aminophthalylhydrazide) is a known example of a chemiluminogen molecule. In the presence of hydrogen peroxide, luminol transforms to amino phthalic acid with an emission of blue light (λmax ≈ 420 nm). The high sensitivity of this reaction determines the effectiveness of the luminol chemiluminescence in bioimaging for the detection of reactive oxygen species.

Here we present the first chemiluminescent poly(2-oxazoline)s, bearing luminol units. Using the post-polymerization modification strategy, we created a library of well-defined statistical and block-copolymers with a variable luminol content. Chemiluminescence emission studies confirm the high sensitivity of obtained copolymers to the reactive oxygen species (H₂O₂) in aqueous solution, comparable to free luminol.
Apart from that, we investigated the ability of the excited luminol units on the polymer to transfer their energy to the model acceptor compound without emission of the photon - chemiluminescent resonance energy transfer (CRET).

The above-described studies display the prospectiveness of luminol-containing poly(2-oxazoline)s for designing ROS-responsive materials for diagnostics and therapy.

Acknowledgment
This research was supported by the Alexander von Humboldt Foundation.

Supramolecular polymers (SMPs) have garnered significant interest due to their inherent stimuli-responsiveness, which imparts advanced properties such as self-healing, reprocessability, and shape memory. However, synthesizing these materials typically requires de novo synthesis, limiting their mechanical properties. Recent developments in our lab aim to streamline the synthesis of responsive materials by modifying commercial polymers.
Creating supramolecular materials from commercially available polymers is a promising strategy to implement responsiveness into widely used materials, thereby increasing applicability and expanding their range of properties. In our first approach, we depolymerized glycol-modified polyethylene terephthalate (PETG) and end-capped it with the 2,6-bis(1′-methylbenzimidazolyl)pyridine (Mebip) tridentate ligand, in one or two steps. Metallosupramolecular polymerization yielded glassy polymers that displayed comparable stiffness to the parent polymer and excellent optical and thermal healability. Similarly, we created supramolecular networks by grafting azide-modified 6-(1′-methylbenzimidazolyl)pyridine (MBP)5 bidentate ligand onto polybutadiene in a single step. The addition of metal ions (Zn²⁺, Ni²⁺, and Mg²⁺) yielded metallosupramolecular rubbers whose properties could be tuned by varying the metal center and the metal-to-ligand ratio.
With these novel approaches to creating supramolecular polymers, we aim to simplify and expand the applicability of this class of materials by enhancing their modularity and broadening the range of their properties.