Noble Metal-Free Light-Driven Hydrogen Evolution Catalysis in Polyampholytic Hydrogel Networks.

Future technologies to harness solar energy and to convert this into chemical energy strongly rely on straightforward approaches to prepare versatile soft matter scaffolds for the immobilization of catalysts and sensitizers in a defined environment. In addition, particularly for light-driven hydrogen evolution, a transition to noble metal-free photosensitizers and catalysts is urgently required. Herein, we report a fully organic light-harvesting soft matter network based on a polyampholyte hydrogel where both photosensitizer (a perylene monoimide derivative) and a H2 evolution catalyst ([Mo3S13]2-) are electrostatically incorporated. The resulting material exhibits sustained visible-light-driven H2 evolution in aqueous ascorbic acid solution, even at rather low loadings of photosensitizer (0.4%) and catalyst (120 ppm). In addition, we provide initial insights into the long-term stability of the hybrid hydrogel. We believe that these results pave the way for a generalized route toward the incorporation of noble metal-free light-driven catalysis in soft matter networks.

Organ-on-chip models for infectious disease research.

Research on microbial pathogens has traditionally relied on animal and cell culture models to mimic infection processes in the host. Over recent years, developments in microfluidics and bioengineering have led to organ-on-chip (OoC) technologies. These microfluidic systems create conditions that are more physiologically relevant and can be considered humanized in vitro models. Here we review various OoC models and how they have been applied for infectious disease research. We outline the properties that make them valuable tools in microbiology, such as dynamic microenvironments, vascularization, near-physiological tissue constitutions and partial integration of functional immune cells, as well as their limitations. Finally, we discuss the prospects for OoCs and their potential role in future infectious disease research.

Tailoring the Degradation Time of Polycationic PEG-Based Hydrogels toward Dynamic Cell Culture Matrices.

Poly(ethylene glycol)-based (PEG) hydrogels provide an ideal platform to obtain well-defined and tailor-made cell culture matrices to enhance in vitro cell culture conditions, although cell adhesion is often challenging when the cells are cultivated on the substrate surface. We herein demonstrate two approaches for the synthesis of polycationic PEG-based hydrogels which were modified to enhance cell-matrix interactions, to improve two-dimensional (2D) cell culture, and catalyze hydrolytic degradation. While the utilization of N,N-(bisacryloxyethyl) amine (BAA) as cross-linker for in situ gelation provides degradable scaffolds for dynamic cell culture, the incorporation of short segments of poly(N-(3-(dimethylamino)propyl)acrylamide) (PDMAPAam) provides high local cationic charge density leading to PEG-based hydrogels with high selectivity for fibroblastic cell lines. The adsorption of transforming growth factor (TGF-ß) into the hydrogels induced stimulation of fibrosis and thus the formation of collagen as a natural ECM compound. With this, these dynamic hydrogels enhance in vitro cell culture by providing a well-defined, artificial, and degradable matrix that stimulates cells to produce their own natural scaffold within a defined time frame.

Poly(dehydroalanine)-Based Hydrogels as Efficient Soft Matter Matrices for Light-Driven Catalysis.

Soft matter integration of photosensitizers and catalysts provides promising solutions to developing sustainable materials for energy conversion. Particularly, hydrogels bring unique benefits, such as spatial control and 3D-accessibility of molecular units, as well as recyclability. Herein, the preparation of polyampholyte hydrogels based on poly(dehydroalanine) (PDha) is reported. Chemically crosslinked PDha with bis-epoxy poly(ethylene glycol) leads to a transparent, self-supporting hydrogel. Due to the ionizable groups on PDha, this 3D polymeric matrix can be anionic, cationic, or zwitterionic depending on the pH value, and its high density of dynamic charges has a potential for electrostatic attachment of charged molecules. The integration of the cationic molecular photosensitizer [Ru(bpy)3 ]2+ (bpy = 2,2'-bipyridine) is realized, which is a reversible process controlled by pH, leading to light harvesting hydrogels. They are further combined with either a thiomolybdate catalyst ([Mo3 S13 ]2- ) for hydrogen evolution reaction (HER) or a cobalt polyoxometalate catalyst (Co4 POM = [Co4 (H2 O)2 (PW9 O34 )2 ]10- ) for oxygen evolution reaction (OER). Under the optimized condition, the resulting hydrogels show catalytic activity in both cases upon visible light irradiation. In the case of OER, higher photosensitizer stability is observed compared to homogeneous systems, as the polymer environment seems to influence decomposition pathways.

Two-Color Spatially Resolved Tuning of Polymer-Coated Metasurfaces.

For the realization of truly reconfigurable metasurface technologies, dynamic spatial tuning of the metasurface resonance is required. Here we report the use of organic photoswitches as a means for the light-induced spatial tuning of metasurface resonances. Coating of a dielectric metasurface, hosting high-quality-factor resonances, with a spiropyran (SPA)-containing polymer enabled dynamic resonance tuning up to 4 times the resonance full-width at half-maximum with arbitrary spatial precision. A major benefit of employing photoswitches is the broad toolbox of chromophores available and the unique optical properties of each. In particular, SPA and azobenzene (AZO) photoswitches can both be switched with UV light but exhibit opposite refractive index changes. When applied to the metasurface, SPA induced a red shift in the metasurface resonance with a figure of merit of 97 RIU-1, while AZO caused a blue shift in the resonance with an even greater sensitivity of 100 RIU-1. Critically, SPA and AZO can be individually recovered with red and blue light, respectively. To exploit this advantage, we coated a dielectric metasurface with spatially offset SPA- and AZO-containing polymers to demonstrate wavelength-dependent, spatially resolved control over the metasurface resonance tuning.

Asymmetric Block Extension of Star-Shaped [PEG-SH]4 - toward Poly(dehydroalanine)-Functionalized PEG Hydrogels for Catch and Release of Charged Guest Molecules.

With the incorporation of polyampholytic segments into soft matter, hydrogels can serve as a reservoir for a variety of charged molecules which can be caught and released upon changes in pH value. Asymmetric block extension of one arm for star-shaped poly(ethylene glycol) [PEG26 -SH]4 using short segments of polyampholytic poly(dehydroalanine) (PDha) is herein demonstrated while maintaining the functional thiol end groups for network formation. For subsequent hydrogel synthesis with up to 10 wt.% PDha a straightforward and biocompatible photoinitiated thiol-ene click reaction is exploited. The investigation of the swelling properties of the hydrogel revealed responsive behavior toward ionic strength and variations in pH value. Moreover, the reversible adsorption of the model dyes methylene blue (MB) and acid orange 7 (AO7) is investigated by UV-vis measurements and the procedure can be successfully transferred to the adsorption of the adhesion peptide RGDS resulting in an uptake of 1.5 wt% RGDS with regard to the dry weight of the hydrogel.

Self-Degrading Multifunctional PEG-Based Hydrogels-Tailormade Substrates for Cell Culture.

The use of PEG-based hydrogels as cell culture matrix to mimic the natural extracellular matrix (ECM) has been realized using a range of well-defined, tunable, and dynamic scaffolds, although they require cell adhesion ligands such as RGDS-peptide (Arg-Gly-Asp-Ser) to promote cell adhesion. Herein the synthesis of ionic and degradable hydrogels is demonstrated for cell culture by crosslinking [PEG-SH]4 with the zwitterionic crosslinker N,N-bis(acryloxyethyl)-N-methyl-N-(3-sulfopropyl) ammonium betaine (BMSAB) and the cationic crosslinker N,N-bis(acryloxyethyl)-N,N-dimethyl-1-ammonium iodide (BDMAI). Depending on the amount of ionic crosslinker used in gel formation, the hydrogels show tunable gelation time and stiffness. At the same time, the ionic groups act as catalysts for hydrolytic degradation, thereby allowing to define a stability window. The latter could be tailored in a straightforward manner by introducing the non-degradable crosslinker tri(ethylene glycol) divinyl ether. In addition, both ionic crosslinkers favor cell attachment in comparison to the pristine PEG hydrogels. The degradation is examined by swelling behavior, rheology, and fluorescence correlation spectroscopy indicating degradation kinetics depending on diffusion of incorporated fluorescent molecules.

Polyoxometalate-Modified Amphiphilic Polystyrene-block-poly(2-(dimethylamino)ethyl methacrylate) Membranes for Heterogeneous Glucose to Formic Acid Methyl Ester Oxidation.

Herein, we present a new heterogeneous catalyst active toward glucose to formic acid methyl ester oxidation. The catalyst was fabricated via electrostatic immobilization of the inorganic polyoxometalate HPA-5 catalyst H8[PMo7V5O40] onto the pore surface of amphiphilic block copolymer membranes prepared via non-solvent-induced phase separation (NIPS). The catalyst immobilization was achieved via wet impregnation due to strong coulombic interactions between protonated tertiary amino groups of the polar poly(2-(dimethylamino)ethyl methacrylate) block and the anionic catalyst. Overall, three sets of five consecutive catalytic cycles were performed in an autoclave under 90 °Ð¡ and 11.5 bar air pressure in methanol, and the corresponding yields of formic acid methyl ester were quantified via head-space gas chromatography. The obtained results demonstrate that the membrane maintains its catalytic activity over multiple cycles, resulting in high to moderate yields in comparison to a homogeneous catalytic system. Nevertheless, presumably due to leaching, the catalytic activity declines over five catalytic cycles. The morphological and chemical changes of the membrane during the prolonged catalysis under harsh conditions were examined in detail using different analytic tools, and it seems that the underlying block copolymer is not affected by the catalytic process.

Self-Assembly of Core-Shell Hybrid Nanoparticles by Directional Crystallization of Grafted Polymers.

Nanoparticle self-assembly is an efficient bottom-up strategy for the creation of nanostructures. In a typical approach, ligands are grafted onto the surfaces of nanoparticles to improve the dispersion stability and control interparticle interactions. Ligands then remain secondary and usually are not expected to order significantly during superstructure formation. Here, we investigate how ligands can play a more decisive role in the formation of anisotropic inorganic-organic hybrid materials. We graft poly(2-iso-propyl-2-oxazoline) (PiPrOx) as a crystallizable shell onto SiO2 nanoparticles. By varying the PiPrOx grafting density, both solution stability and nanoparticle aggregation behavior can be controlled. Upon prolonged heating, anisotropic nanostructures form in conjunction with the crystallization of the ligands. Self-assembly of hybrid PiPrOx@SiO2 (shell@core) nanoparticles proceeds in two steps: First, the rapid formation of amorphous aggregates occurs via gelation, mediated by the interaction between nanoparticles through grafted polymer chains. As a second step, slow radial growth of fibers was observed via directional crystallization, governed by the incorporation of crystalline ribbons formed from free polymeric ligands in combination with crystallization of the covalently attached ligand shell. Our work reveals how crystallization-driven self-assembly of ligands can create intricate hybrid nanostructures.

Tailoring the Weight of Surface and Intralayer Edge States to Control LUMO Energies.

The energies of the frontier molecular orbitals determine the optoelectronic properties in organic films, which are crucial for their application, and strongly depend on the morphology and supramolecular structure. The impact of the latter two properties on the electronic energy levels relies primarily on nearest-neighbor interactions, which are difficult to study due to their nanoscale nature and heterogeneity. Here, an automated method is presented for fabricating thin films with a tailored ratio of surface to bulk sites and a controlled extension of domain edges, both of which are used to control nearest-neighbor interactions. This method uses a Langmuir-Schaefer-type rolling transfer of Langmuir layers (rtLL) to minimize flow during the deposition of rigid Langmuir layers composed of π-conjugated molecules. Using UV-vis absorption spectroscopy, atomic force microscopy, and transmission electron microscopy, it is shown that the rtLL method advances the deposition of multi-Langmuir layers and enables the production of films with defined morphology. The variation in nearest-neighbor interactions is thus achieved and the resulting systematically tuned lowest unoccupied molecular orbital (LUMO) energies (determined via square-wave voltammetry) enable the establishment of a model that functionally relates the LUMO energies to a morphological descriptor, allowing for the prediction of the range of accessible LUMO energies.

Straightforward Access to Block and Gradient Light-Responsive Poly(2-Oxazoline)S via Cationic Ring Opening Polymerization Of 2-Azobenzenyl-2-Oxazoline.

Light-responsive polymers are a prospective area of smart materials. The increasing number of potential applications of these materials require the development of new polymers sensitive to external irradiation. However, most of the polymers reported so far are represented by poly(meth)acrylates. In this work, the straightforward approach is proposed to the synthesis of light-responsive poly(2-oxazoline)s via cationic ring-opening polymerization of 2-azobenzenyl-2-oxazoline (2-(4-(phenyldiazenyl)phenyl)-2-oxazoline). Polymerization kinetics studies reveal significant activity of the new monomer in both homopolymerization and copolymerization with 2-ethyl-2-oxazoline. The difference in monomer reactivity allows obtaining both gradient and block copolymers via simultaneous or subsequent one-pot polymerization, respectively, leading to a set of well-defined gradient and block copoly(2-oxazoline)s with 10-40% of azobenzene units. Due to their amphiphilic nature, the materials self-assemble in water, which is proven by dynamic light scattering and transmission electron microscopy. The change in polarity caused by the isomerization of azobenzene fragments in response to UV light irradiation results in a change of nanoparticle size. The obtained results provide a new impulse for the development of light-responsive materials based on poly(2-oxazoline)s.

Optimization of Magnetic Cobalt Ferrite Nanoparticles for Magnetic Heating Applications in Biomedical Technology.

Using magnetic nanoparticles for extracorporeal magnetic heating applications in bio-medical technology allows higher external field amplitudes and thereby the utilization of particles with higher coercivities (HC). In this study, we report the synthesis and characterization of high coercivity cobalt ferrite nanoparticles following a wet co-precipitation method. Particles are characterized with magnetometry, X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy (TEM) and calorimetric measurements for the determination of their specific absorption rate (SAR). In the first series, CoxFe3-xO4 particles were synthesized with x = 1 and a structured variation of synthesis conditions, including those of the used atmosphere (O2 or N2). In the second series, particles with x = 0 to 1 were synthesized to study the influence of the cobalt fraction on the resulting magnetic and structural properties. Crystallite sizes of the resulting particles ranged between 10 and 18 nm, while maximum coercivities at room temperatures of 60 kA/m for synthesis with O2 and 37 kA/m for N2 were reached. Magnetization values at room temperature and 2 T (MRT,2T) up to 60 Am2/kg under N2 for x = 1 can be achieved. Synthesis parameters that lead to the formation of an additional phase when they exceed specific thresholds have been identified. Based on XRD findings, the direct correlation between high-field magnetization, the fraction of this antiferromagnetic byphase and the estimated transition temperature of this byphase, extracted from the Mössbauer spectroscopy series, we were able to attribute this contribution to akageneite. When varying the cobalt fraction x, a non-monotonous correlation of HC and x was found, with a linear increase of HC up to x = 0.8 and a decrease for x > 0.8, while magnetometry and in-field Mössbauer experiments demonstrated a moderate degree of spin canting for all x, yielding high magnetization. SAR values up to 480 W/g (@290 kHz, 69 mT) were measured for immobilized particles with x = 0.3, whit the external field amplitude being the limiting factor due to the high coercivities of our particles.

Diiodo-BODIPY Sensitizing of the [Mo3S13]2- Cluster for Noble-Metal-Free Visible-Light-Driven Hydrogen Evolution within a Polyampholytic Matrix.

We report on a photocatalytic setup that utilizes the organic photosensitizer (PS) diiodo-BODIPY and the non-precious-metal-based hydrogen evolution reaction (HER) catalyst (NH4)2[Mo3S13] together with a polyampholytic unimolecular matrix poly(dehydroalanine)-graft-poly(ethylene glycol) (PDha-g-PEG) in aqueous media. The system shows exceptionally high performance with turnover numbers (TON > 7300) and turnover frequencies (TOF > 450 h-1) that are typical for noble-metal-containing systems. Excited-state absorption spectra reveal the formation of a long-lived triplet state of the PS in both aqueous and organic media. The system is a blueprint for developing noble-metal-free HER in water. Component optimization, e.g., by modification of the meso substituent of the PS and the composition of the HER catalyst, is further possible.

Multimodal Analysis of Light-Driven Water Oxidation in Nanoporous Block Copolymer Membranes.

Heterogeneous light-driven catalysis is a cornerstone of sustainable energy conversion. Most catalytic studies focus on bulk analyses of the hydrogen and oxygen evolved, which impede the correlation of matrix heterogeneities, molecular features, and bulk reactivity. Here, we report studies of a heterogenized catalyst/photosensitizer system using a polyoxometalate water oxidation catalyst and a model, molecular photosensitizer that were co-immobilized within a nanoporous block copolymer membrane. Via operando scanning electrochemical microscopy (SECM), light-induced oxygen evolution was determined using sodium peroxodisulfate (Na2 S2 O8 ) as sacrificial electron acceptor. Ex situ element analyses provided spatially resolved information on the local concentration and distribution of the molecular components. Infrared attenuated total reflection (IR-ATR) studies of the modified membranes showed no degradation of the water oxidation catalyst under the reported light-driven conditions.

Inside Block Copolymer Micelles-Tracing Interfacial Influences on Crosslinking Efficiency in Nanoscale Confined Spaces.

Recently, several studies have demonstrated the excellent capabilities of tip-enhanced Raman spectroscopyfor in-depth investigations of structural properties of matter with unprecedented resolution and chemical specificity. These capabilities are utilized here to study the internal structure of core-crosslinked micelles, which are formed by self-assembly of the diblock terpolymer poly(ethylene oxide)-block-poly(furfuryl glycidylether-co-tert-butylglycidyl ether). Supplementing force-volume atomic force microscopy experiments address additionally the nanomechanical properties. Particularly, TERS enables investigating the underlying principles influencing the homogeneity and efficiency of the Diels-Alder core-crosslinking process in the confined hydrophobic core. While the central core region is homogenously crosslinked, a breakdown of the crosslinking reaction is observed in the core-corona interfacial region. The results corroborate that a strong crosslinking efficiency is directly correlated to the formation of a mixed zone of the glycidyl ether and PEO corona blocks reaching ≈5 nm into the core region. Concomitantly a strong exclusion of the encapsulated bismaleimide crosslinker from the interfacial region is observed. It is conceivable that a changed structure, chemical composition and altered nanomechanical properties of this interfacial region may also influence the crosslinking efficiency across the entire core region by a modification of the solubility of the crosslinker in the interfacial core-corona region.

Tuning the corona-core ratio of polyplex micelles for selective oligonucleotide delivery to hepatocytes or hepatic immune cells.

Targeted delivery of oligonucleotides or small molecular drugs to hepatocytes, the liver's parenchymal cells, is challenging without targeting moiety due to the highly efficient mononuclear phagocyte system (MPS) of the liver. The MPS comprises Kupffer cells and specialized sinusoidal endothelial cells, efficiently clearing nanocarriers regardless of their size and surface properties. Physiologically, this non-parenchymal shield protects hepatocytes; however, these local barriers must be overcome for drug delivery. Nanocarrier structural properties strongly influence tissue penetration, in vivo pharmacokinetics, and biodistribution profile. Here we demonstrate the in vivo biodistribution of polyplex micelles formed by polyion complexation of short interfering (si)RNA with modified poly(ethylene glycol)-block-poly(allyl glycidyl ether) (PEG-b-PAGE) diblock copolymer that carries amino moieties in the side chain. The ratio between PEG corona and siRNA complexed PAGE core of polyplex micelles was chemically varied by altering the degree of polymerization of PAGE. Applying Raman-spectroscopy and dynamic in silico modeling on the polyplex micelles, we determined the corona-core ratio (CCR) and visualized the possible micellar structure with varying CCR. The results for this model system reveal that polyplex micelles with higher CCR, i.e., better PEG coverage, exclusively accumulate and thus allow passive cell-type-specific targeting towards hepatocytes, overcoming the macrophage-rich reticuloendothelial barrier of the liver.

Amphiphilic Graft Copolymers for Time-Delayed Release of Hydrophobic Fragrances.

When a controlled or retarded release of perfumes is required such as in cosmetics or cleaning products, polymers can be applied as encapsulation agents. With regard to such applications, we investigated two amphiphilic graft copolymers featuring a polydehydroalanine (PDha) backbone and different hydrophobic side chains. Hereby, grafting of aliphatic octyl side chains (PDha-g-EOct) enabled the adsorption of the aliphatic fragrance tetrahydrolinalool with moderate loads, whereas benzyl side chains (PDha-g-BGE) allowed taking up aromatic fragrances, for example, amylsalicylate-n with exceptionally high loads of up to 8 g g-1. The side-chain density was studied as well but had no significant influence on the loading. In addition, the characterization and quantification of the load by NMR and thermogravimetric analysis were compared, and it was also possible to load the aromatic model fragrance into the graft copolymer with aliphatic side chains. After 3 months, the load had decreased by 40-50% and, hence, such systems are of interest for a long-term release of perfumes over months. Although this study is a proof-of-concept, we foresee that such polyampholytic graft copolymers can be tailored for the adsorption of a variety of hydrophobic perfumes simply by altering polarity and chemistry of the side chain.

In Situ SERS Sensing by a Laser-Induced Aggregation of Silver Nanoparticles Templated on a Thermoresponsive Polymer.

A stimuli-responsive (pH- and thermoresponsive) micelle-forming diblock copolymer, poly(1,2-butadiene)290-block-poly(N,N-dimethylaminoethyl methacrylate)240 (PB-b-PDMAEMA), was used as a polymer template for the in situ synthesis of silver nanoparticles (AgNPs) through Ag+ complexation with PDMAEMA blocks, followed by the reduction of the bound Ag+ with sodium borohydride. A successful synthesis of the AgNPs on a PB-b-PDMAEMA micellar template was confirmed by means of UV-Vis spectroscopy and transmission electron microscopy, wherein the shape and size of the AgNPs were determined. A phase transition of the polymer matrix in the AgNPs/PB-b-PDMAEMA metallopolymer hybrids, which results from a collapse and aggregation of PDMAEMA blocks, was manifested by changes in the transmittance of their aqueous solutions as a function of temperature. A SERS reporting probe, 4-mercaptophenylboronic acid (4-MPBA), was used to demonstrate a laser-induced enhancement of the SERS signal observed under constant laser irradiation. The local heating of the AgNPs/PB-b-PDMAEMA sample in the laser spot is thought to be responsible for the triggered SERS effect, which is caused by the approaching of AgNPs and the generation of "hot spots" under a thermo-induced collapse and the aggregation of the PDMAEMA blocks of the polymer matrix. The triggered SERS effect depends on the time of a laser exposure and on the concentration of 4-MPBA. Possible mechanisms of the laser-induced heating for the AgNPs/PB-b-PDMAEMA metallopolymer hybrids are discussed.

Rapid determination of key impurities in high purity bisphenol A with reversed phase separation and triple quadrupole mass spectrometry.

Liquid chromatography with diode array detection (DAD) or ultraviolet spectroscopic (UV) detection as the most important analytical technique for the accurate quantification of impurities in bisphenol compounds normally requires long analysis time for baseline separation of all components as well as highly concentrated sample solutions for the detection of trace levels. To expand the application possibilities to all stages of polymerisation processes, an easy and robust reversed phase separation for 7 known impurities of bisphenol-A (BPA) including 4-isopropenylphenol and its dimeric isomers, o, p-bisphenol-A and trisphenol was established in this work. The method has been validated for the detection with triple quadrupole mass spectrometry (qqqMS) and DAD. In the investigated concentration range 0.5 - 100 mg/kg, the linearity is verified for both detection techniques. The limit of quantification (LOQ) for each impurity is with 0.5 - 1.5 mg/kg for qqqMS and 15 mg/kg for DAD sufficient for the evaluation of BPA as a raw material for polymerisation processes. The separation time for all impurities is 10 min whereas earlier reported methods need a minimum of 25 to 40 min. In addition the necessary sample concentration of BPA could be reduced to 5 mg/mL compared to existing methods where the sample concentration typically is > 50 mg/mL. For all those reasons the validated method can be efficiently applied for frequent process monitoring. Furthermore, 4 additional impurities were detected and identified. Mainly these are reaction products from the isopropenylphenol structure in combination with confirmed impurities as trisphenol or chroman. The quantification of these structures was established with trisphenol as reference and two structures were detected in all BPA qualities of this study in a concentration range from 20 - 400 mg/kg.

Double hydrophilic copolymers - synthetic approaches, architectural variety, and current application fields.

Solubility and functionality of polymeric materials are essential properties determining their role in any application. In that regard, double hydrophilic copolymers (DHC) are typically constructed from two chemically dissimilar but water-soluble building blocks. During the past decades, these materials have been intensely developed and utilised as, e.g., matrices for the design of multifunctional hybrid materials, in drug carriers and gene delivery, as nanoreactors, or as sensors. This is predominantly due to almost unlimited possibilities to precisely tune DHC composition and topology, their solution behavior, e.g., stimuli-response, and potential interactions with small molecules, ions and (nanoparticle) surfaces. In this contribution we want to highlight that this class of polymers has experienced tremendous progress regarding synthesis, architectural variety, and the possibility to combine response to different stimuli within one material. Especially the implementation of DHCs as versatile building blocks in hybrid materials expanded the range of water-based applications during the last two decades, which now includes also photocatalysis, sensing, and 3D inkjet printing of hydrogels, definitely going beyond already well-established utilisation in biomedicine or as templates.