Electrochemically responsive polymer brushes that can undergo a transition between a swollen and collapsed state in response to an electrical potential hold considerable promise for incorporation into "smart devices". Despite their significant advantages, this type of switching trigger has received only minor attention. Our study demonstrates that the hexacyanoferrate redox pair induces rapid conformational changes in permanently positively charged polymer brushes due to changes in the electrode potential. These films were prepared by quaternizing poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes grafted onto gold and silicon substrates by using a robust, reproducible grafting-to approach. Insights into the electrochemically induced complexation behavior of strong polyelectrolyte brushes are gained by combining the results of static spectroscopic in situ ellipsometry measurements and dynamic measurements using an electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D). This knowledge is applied to determine the optimal hexacyanoferrate concentration for the switching of such brushes under an electric potential. Our findings reveal that switching under optimized conditions occurs within the millisecond range, showcasing the potential of this underrepresented switching trigger.

The design of vacuum-processed organic solar cells requires a balance between optimizing energetic and morphological properties for efficient photovoltaic performance. In this study, we investigate two structurally similar molecular donors, DCV-iPr and DCV-Me, which exhibit stark differences in photovoltaic performance despite their minimal chemical differences. Through a combined experimental and theoretical approach-including crystal structure prediction, vapor deposition simulations, GIWAXS measurements, and advanced electronic structure calculations-we establish how molecular packing influences optical absorption and photovoltaic efficiency. Our findings show that steric effects introduced by the isopropyl group in DCV-iPr lead to a brick-wall molecular arrangement, favoring J-like excitonic interactions and resulting in sharp optical absorption with a reduced Stokes shift. In contrast, DCV-Me forms a more H-like aggregation, leading to broadened absorption and higher voltage losses. While DCV-iPr demonstrates enhanced photovoltaic performance, we identify substantial remaining voltage losses associated with charge-transfer excitations at the donor-acceptor interface. This work provides key design guidelines linking molecular packing to optical absorption properties and highlights the need for alternative acceptor materials with steeper absorption onsets to further optimize vacuum-processed organic solar cells.

The aggregation behavior of dipyrrolonaphthyridinedione (DPND) chromophores in the solid state critically determines their optoelectronic properties. Here, we investigate how systematic variation in the side-chain geometry-specifically the branching point and steric profile-governs molecular packing and excitonic coupling. Using crystal structure prediction (CSP) combined with experimental GIWAXS and solid-state NMR, we obtain the packing geometry and crystal structure for three DPND derivatives (DPND-iPr, DPND-EtPr, and DPND-iBu). The results reveal that side-chain branching at the first carbon atom promotes herringbone packing and J-type behavior, while branching at the second carbon induces brick-wall stacking and H-type behavior in the solid state. Optical simulations based on the Holstein exciton-vibrational Hamiltonian reproduce experimental absorption and photoluminescence spectra, confirming the transition from J-like to H-like photophysics as the side-chain branching position shifts. This study demonstrates that fine-tuning alkyl side-chain geometry enables rational control of aggregation and excitonic behavior in cross-conjugated DPNDs, providing new design principles for functional organic semiconductors.

The development of nontoxic, thermally and mechanically stable, efficient, and metal-free carbonaceous materials has gained significant attention owing to their promising applications in adsorption and catalytic removal of organic pollutants. This study reports the synthesis of N-doped carbonaceous structures from chitosan-coated sand particles calcined at 500-800 degrees C. The obtained materials, integrating low cost, scalability, and environmental safety, were investigated as bifunctional composites for phenol degradation through the synergistic action of adsorption and peroxymonosulfate (PMS) activation. The structure and morphology of the composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Raman spectroscopy. Among the developed samples, the CCS-500 specimen calcined at 500 degrees C demonstrated the highest phenol adsorption and degradation efficiency, primarily due to its superior adsorption capacity. Under optimized conditions of catalyst dosage, PMS concentration, initial phenol concentration and pH, CCS-500 achieved nearly complete phenol removal. This superior performance is related to its elevated carbon content and the relatively low density of structural defects within its graphitic carbon.

In industrial parts cleaning and metal processing, there are currently no filmic model soiling’s that make it possible to generate homogeneous soiling films independent of geometry. However, this is essential for defined and reproducible cleaning tests. Polymer based coatings can close this gap. In the work presented here, a suitable optimised copolymer with carboxy groups as adhesive groups was developed and investigated for this application purpose. The polymer's cleaning behaviour, and therefore its adhesion, is adapted to that of a reference soiling. A fluorescent dye was attached to the polymer for subsequent detection and a dipping process was developed for the defined application of the copolymer. Comprehensive layer characterisation and systematic cleaning tests using ultrasound proved the reproducibility and uniformity of the generated layers. The residual layers of the polymer after each cleaning step could be quantified both by means of ellipsometry on smooth substrates and by measuring the fluorescence intensity. The process was extended to complex three-dimensional geometries and tested on cleaning systems in an industrial environment in order to validate the applicability, practicability, and efficiency of the developed method. The results show that the selected polymer concept provides a promising solution for the production of a uniform model soiling in component cleaning.

Understanding the interplay between the molecular structure of the ionic liquid (IL) subunit, the resulting nanostructure and ion transport in polymerized ionic liquids (PILs) is necessary for the realization of high-performance solid-state electrolytes required in various advanced applications. Herein, we present a detailed structural characterization of a recently synthesized series of acrylate-based PIL homopolymers and networks with imidazolium cations and chloride anions with varying alkyl spacer and terminal group lengths designed for organic solid-state batteries based on X-ray scattering. The impact of the concentrations of both the crosslinker and added tetrabutylammonium chloride (TBACl) conducting salt on the structural characteristics is also investigated. The results reveal that the length of both the spacer and terminal group influence the chain packing and, in turn, the nanophase segregation of the polar domains. Long spacers and terminal groups seem to induce denser polar aggregates sandwiched between more compact alkyl spacer and terminal group domains. However, the large inter-backbone spacing achieved seems to limit the ionic conductivity of these PILs. More importantly, our findings show that the previously reported general relationships between the ionic conductivity and the structural parameters of the nanostructure of PILs are not always attainable for different molecular structures of the IL side group.

We resolve the Schröder paradox for PNiPAAm brushes, showing experimentally that swelling at 100% relative humidity (RH) matches the liquid state. This occurs via a sharp increase in swelling above 98% RH, a behavior standard models fail to explain. Our extended mean-field theory explains this via a positive feedback between swelling and solvent quality, driven by a concentration-dependent χ parameter. The swelling isotherm quantitatively predicts the dynamic wetting crossover: the advancing contact angle at high velocities drops sharply as ambient humidity surpasses the 98% RH threshold.

Weak polyelectrolyte brushes represent a versatile class of responsive surface coatings. The adjustment of their charges by modifying the pH value and the salt content of the surrounding solution has a considerable effect on the elongation of the brush, the interaction between the chains, and the degree of swelling. Recent studies have extensively demonstrated the impact of singly charged cations through theoretical and experimental means. Analyses of the interaction between polyacids and multicharged cations remain underrepresented. Therefore, the influence of multivalent cations (Ca2+ and Ce3+) on the swelling behavior of poly(acrylic acid) (PAA) brushes is investigated as a function of salt concentration and pH. Swelling measurements show a behavior that differs significantly from the well-known case of monovalent cations. To elucidate this anomalous behavior, this study employs a combination of in situ spectroscopic ellipsometry, atomic force microscopy (AFM), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The investigations reveal a highly intricate interaction behavior, which can be ascribed to the multivalency of the cations utilized. The FTIR measurements indicate the impact of the cations on the pKa value of the brush and the dissociation behavior. This study provides insights into the charging properties of PAA brushes, highlighting the decisive additional influence of the valency of the cations in combination with their concentration. Multivalent ions have been observed to substitute for the protons of the carboxyl groups through an entropically driven process, resulting in degrees of dissociation, α > 0.5, even at a pH of 3, where PAA brushes are expected to be fully undissociated. This phenomenon leads to an increased degree of swelling at very low salt concentrations and a reduction at increasing ionic strength. Evidence was found for different types of ion/carboxylate coordination, with bridging coordination between the carboxyl groups of PAA and the cations.

Hydrophilic adaptive polymer coatings, such as poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) films, are characterized by high hydrophilicity and swelling, which is caused by unique interactions with water molecules based on their molecular structure. This specific behavior allows for the discussion of various potential applications, including easy-to-clean, protein resistance, anti-fouling or anti-fog properties. However, a major drawback in the implementation of these coatings is their stability in aqueous environments, which is a common limitation of hydrophilic polymer films, even when they are chemically grafted to the substrate. In this study, SiO2 model surfaces were used to demonstrate that it is feasible to markedly enhance the water stability of thin grafted poly(MPC) films while preserving their functionality subsequent to water treatment. To this end, a set of three copolymers of MPC with varying amounts of glycidyl methacrylate (GMA) were synthesized, in which GMA serves the dual role of crosslinker and coupling agent. The impact of copolymer composition and grafting time on film stability was examined through the implementation of water performance tests in combination with spectroscopic in situ ellipsometry measurements. The optimization of polymer composition and grafting time resulted in the development of polymer layers that exhibited stability for a minimum of 100 days in water at room temperature and for 24 h in boiling water. The optimized films retained their easy-to-clean properties subsequent to the water performance tests.

Hybrid materials composed of conducting polymers and magnetic iron oxide nanoparticles (NPs) have an expanding range of novel applications including biomedicine, shielding of electromagnetic interference, sensors, electrochemical capacitors and adsorption of dyes. In this study, we developed highly dispersed, crystalline, magnetic and conductive camphor sulfonic acid protonated polyaniline/iron oxide (PANI-CSA/IO) nanocomposite films from aqueous solution by potentiostatic electrochemical polymerization. The structural, optical, electrical, magnetic and morphological characteristics of the prepared nanocomposite films have been investigated. Interestingly, the crystallization process of the PANI chains led to the dispersion of the IO NPs suppressing their crystallization in the films. It was also observed that the pi-pi* band gap energy of the nanocomposite films increased with increasing the concentration of IO NPs. In addition, almost 2-fold increase in the magnetization of the nanocomposite film was achieved by increasing the concentration of the IO NPs from 3 to 12 wt%. In contrast, the electrical conductivity showed inverse relationship with the IO NPs concentration. This behavior is related to the interplay between a nucleating effect and molecular interaction with the PANI chains of the embedded IO NPs depending on their concentration. At low concentration, the nucleating effect of PANI crystallites is dominant, whereas the molecular interaction takes over at high concentrations. However, the increased presence of the IO NPs hinders the diffusion of the PANI chain segments during crystallization leading to limited crystal growth locally. These findings contribute to the understanding and controlling of the relationship between the self-assembly and physical properties of magnetic NPs/conducting polymer nanocomposite films.

For cleaning tests, which are important in many industrial processes, there are no test contaminations with which geometry-independent homogeneous films can be produced. Polymer films can fill this gap when they are able to mimic the properties of reference contaminants. For this purpose, acrylic acid (AA) copolymers are prepared by conventional atom transfer radical copolymerization and subsequent acidolysis of the tert-butyl acrylate (tBA) prepolymers. In this way polarity and adhesion can be adjusted by the amount of carboxy groups in the polymer. Dynamic contact angle measurements show that the advancing contact angle of acrylic acid/methyl(meth)acrylate statistical copolymer layers increase with decreasing carboxy group content. Cleaning experiments show accordingly that the amount of residual polymer of coatings made from these polymers is dependent on the absolute number of adhesive carboxy groups in the polymer. Therefore, for an adaption of the polymer layers to hydrophilic reference contaminants it is necessary to incorporate additional hydrophilic monomer components into the polymers, which lead to lower contact angles but also stronger adhesion of the layers. Hence, it is shown that the chosen polymer concept is delivering the leverages to adjust the properties of appropriate test contaminants.

Abstract The creation of novel approaches to reduce the icing of devices is of economic, technical, and ecological interest. Passive deicing approaches based on thin polymer layers show high potential. (Super)hydrophilic films, characterized by high swelling and surface energy, exhibit a self‐lubricating interfacial layer that can influence ice adhesion. For this purpose, a polymer layer consisting of zwitterionic 2‐methacryloyloxyethyl phosphorylcholine (MPC) and glycidyl methacrylate (GMA) is presented and investigated with respect to its icing behavior. The dependence of the swelling behavior of these layers on temperature and a stabilization of the swelling even at low temperatures is shown and can be directly influenced by the grafting conditions, which have a significant impact on the resulting ice thickness and deicing performance. In addition to the formation of a thinner ice layer, the polymer coatings grafted for 16 h are characterized by excellent deicing performance, resulting in consistently very low ice layer thicknesses in repeated icing–deicing cycles compared to the investigated reference SiO2. Due to these properties, the developed film has high application potential as a coating for heat exchangers, as it enables a reduction of the time between defrosting cycles and the distance between the plates, resulting in energy and material savings.

Organic, solid-state batteries require efficient solid electrolytes able to provide stable ion conduction. Here, solid electrolytes based on ionic liquid (IL) polymers with chloride counterions as electrolyte materials for batteries are presented. Acrylic monomers with imidazolium substituents with alkyl side groups that are linked by alkyl spacers to the acrylic group are employed. The IL monomers with chloride counterions are either converted by thermally initiated radical polymerization into linear homopolymers or incorporated into polymer networks by UV-initiated copolymerization utilizing a bifunctional, non-ionic cross-linker. Both procedures successfully yielded the desired materials, which is confirmed by NMR spectroscopy (linear homopolymers) or Raman spectroscopy (IL networks). The ionic conductivities at room temperature are measured by Electrochemical Impedance Spectroscopy. The ionic conductivities of the linear homopolymers are in the range of 10(-4) to 10(-6) S cm(-1), while those of the IL networks are about two orders of magnitude lower. They increase to 10(-4) S cm(-1) at 70 degrees C. The electrochemical stability is examined by Linear Sweep Voltammetry and is proven in the voltage range of -2 to +2 V. The results reveal that the materials represent promising electrolytes for potential solid-state battery applications.

The literature lacks established concrete parameters for assigning grafted chain regimes. In this context, dichroic in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and in situ ellipsometry were used complementarily, offering new opportunities for conformational analysis of end-grafted polymer chains. Especially polymer chain orientation was studied as a new parameter, among others, for proper chain regime assignment in this report. Alkyne-functionalized poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) with a molecular weight of 49.8 kg/mol and a contour length of around 80 nm was grafted to self-assembled monolayers bearing triazole end groups as reported. Different chain regimes were generated by using three different grafting densities. ATR-FTIR spectroscopy based on the ν(C═O) stretching vibration at around 1728 cm-1 provided a new direct approach to determine the GD of polymer chains. Significant shifts in the position of the ν(C═O) band comparing dry and wet states were observed, caused by increased hydrogen bonding interactions between PDMAEMA and water. Finally, the averaged orientation of PDMAEMA chains along the z-axis was determined using dichroic ATR-FTIR spectroscopy based on the dichroic ratios of the ν(C═O) band and molecular order parameters SZ,MOL calculated thereof. High SZ,MOL values were found for the wet state compared to the dry state, confirming that all GD PDMAEMA samples are in the brush regime in the swollen state.

A detailed understanding of the cell adhesion on polymeric surfaces is required to improve the performance of biomaterials. Quartz crystal microbalance with dissipation (QCM-D) as a surface-sensitive technique has the advantage of label-free and real-time monitoring of the cell-polymer interface, providing distinct signal patterns for cell-polymer interactions. In this study, QCM-D was used to monitor human fetal osteoblastic (hFOB) cell adhesion onto polycaprolactone (PCL) and chitosan (CH) homopolymer films as well as their blend films (75:25 and 25:75). Complementary cell culture assays were performed to verify the findings of QCM-D. The thin polymer films were successfully prepared by spin-coating, and relevant properties, i.e., surface morphology, ζ-potential, wettability, film swelling, and fibrinogen adsorption, were characterized. The adsorbed amount of fibrinogen decreased with an increasing percentage of chitosan in the films, which predominantly showed an inverse correlation with surface hydrophilicity. Similarly, the initial cell sedimentation after 1 h resulted in lesser cell deposition as the chitosan ratio increased in the film. Furthermore, the QCM-D signal patterns, which were measured on the homopolymer and blend films during the first 18 h of cell adhesion, also showed an influence of the different interfacial properties. Cells fully spread on pure PCL films and had elongated morphologies as monitored by fluorescence microscopy and scanning electron microscopy (SEM). Corresponding QCM-D signals showed the highest frequency drop and the highest dissipation. Blend films supported cell adhesion but with lower dissipation values than for the PCL film. This could be the result of a higher rigidity of the cell-blend interface because the cells do not pass to the next stages of spreading after secretion of their extracellular matrix (ECM) proteins. Variations in the QCM-D data, which were obtained at the blend films, could be attributed to differences in the morphology of the films. Pure chitosan films showed limited cell adhesion accompanied by low frequency drop and low dissipation.

Polymer brushes, i.e., end-tethered polymer chains on substrates, are sensitive to adaptation, e.g., swelling, adsorption, and reorientation of the surface molecules. This adaptation can originate from a contacting liquid or atmosphere for partially wetted substrates. The macroscopic contact angle of the aqueous drop can depend on both adaptation mechanisms. We analyze how the atmosphere around an aqueous droplet determines the resulting contact angle of the wetting droplet on polymer brush surfaces. Poly(N-isopropylacrylamide) (PNiPAAm)-based brushes are used due to their exceptional sensitivity to solvation and liquid mixture composition. We develop a method that reliably measures wetting properties when the drop and the surrounding atmosphere are not in equilibrium, e.g., when evaporation and condensation tend to contaminate the liquid of the drop and the atmosphere. For this purpose, we use a coaxial needle in the droplet, which continuously exchanges the wetting liquid, and in addition, we constantly exchange the almost saturated atmosphere. Depending on the wetting history, PNiPAAm can be prepared in two states, state A with a large water contact angle (∼65°) and state B with a small water contact angle (∼25°). With the coaxial needle, we can demonstrate that the water contact angle of a sample in state B significantly increases by ∼30° when a water-free atmosphere is almost saturated with ethanol, compared to an ethanol-free atmosphere at 50% relative humidity. For a sample in state A, the relative humidity has little influence on the water contact angle.

Polymeric single chloride-ion conductor networks based on acrylic imidazolium chloride ionic liquid monomers AACXImCYCl as reported previously are prepared. The chemical structure of the polymers is varied with respect to the acrylic substituents (alkyl spacer and alkyl substituent in the imidazolium ring). The networks are examined in detail with respect to the influence of the chemical structure on the resulting properties including thermal behavior, rheological behavior, swelling behavior, and ionic conductivity. The ionic conductivities increase (by two orders of magnitude from 10-6 to 10-4 S·cm-1 with increasing temperature), while the complex viscosities of the polymer networks decrease simultaneously. After swelling in water for 1 week the ionic conductivity reaches values of 10-2 S·cm-1. A clear influence of the spacer and the crosslinker content on the glass transition temperature was shown for the first time in these investigations. With increasing crosslinker content, the Tg values and the viscosities of the networks increase. With increasing spacer length, the Tg values decrease, but the viscosities increase with increasing temperature. The results reveal that the materials represent promising electrolytes for batteries, as proven by successful charging/discharging of a p(TEMPO-MA)/zinc battery over 350 cycles.

Surfaces that respond to local environmental stimuli offer intriguing possibilities for new surface-based sensing concepts to emerge. An attractive concept is to push beyond the milli- to micrometer lateral resolution limit in sensing, toward the ultimate surface-sensitive device; one capable of real-time sensing of the nanoscopic, or molecular "touch." This sensing needs an approach that is capable of spatially transducing information on nanotouch. Polymer brushes are a class of surface that provides dramatic changes in surface properties depending on stimuli that affect the conformation of end-tethered polymer chains. However, the brush response is typically quantified by measuring changes in polymer brush "height". That is, the ensemble average distance over which polymer density exists away from the anchoring surface (i.e., a single parameter to describe the surface). Moving beyond this conceptual paradigm of quantifying the ensemble average height in a single dimension over the entire surface under applied stimuli, developing methods for spatially resolving chain conformation has the very real potential to lead to extraordinary possibilities in the applied sciences. In this perspective, the current paradigms and methods forward for extracting rich details on polymer brush conformational dynamics that is spatially resolved, which can lead to new understandings of surface contact, are discussed and pointed out.

The combination of different wetting states, such as hydrophilic and oleophobic, in an adaptive polymer layer provides new opportunities in the field of easy-to-clean and anti-fog coatings. In this work, the synthesis of new end-functionalized well-defined block copolymers consisting of a hydrophilic poly(acrylic acid) (PAA) block and an oleophobic poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate) (PHFIPMA) block of different block length was investigated. This was achieved by parallel synthesis of the single blocks separately using atom transfer radical polymerization (ATRP), and subsequent block coupling by copper(I)-catalyzed click chemistry. A hydroxy end-group functionalization allowed these polymers to be assembled into dense polymer brushes via a grafting-to approach. The architecture of theses brushes and the orientation of the chains within the films were studied using angle-resolved X-ray photoelectron spectroscopy (ARXPS). To study the influence of the lengths and ratio of the two blocks on the switching of the wettability, contact angle measurements were performed demonstrating the correlation between structure and functionality. It was found that an increasing length of the hydrophilic block, while keeping the length of the oleophobic block constant, leads to an increase of the switching amplitude. Molecular Dynamic Simulations, which gave deeper insights into changes of the brush architecture during switching, enabled in combination with chemical analysis at the nanometer scale (ARXPS) conclusions about the influence of molecular rearrangements inside the brush on macroscopic changes at the outer surface of the brush due to external stimuli. Finally, oil spray-off experiments demonstrated the potential of these new adaptive polymer brushes as easy-to-clean coatings.