ABSTRACT Covalent adaptable networks are an emerging class of polymer networks that exhibit high potential for recyclability. For industrial applications, the robustness of material properties and predictable dynamic behavior are highly desirable. In this study, diepoxides of varying purity were used to prepare hybrid CANs. Hybrid CANs are based on dynamic vinylogous urethane bonds and permanent bonds formed by the reaction of amines and epoxides. The robustness of the materials dynamic exchange behavior against impurities that impair or modify the network characteristics was specifically investigated. Stress relaxation experiments reveal that the dynamic behavior remains relatively stable up to ca. 23% monomer impurity. At higher impurity levels, we observe pronounced changes of the exchange dynamics. All materials, regardless of purity, exhibit incomplete stress relaxation because of the significant fraction of permanent bonds. As a consequence, visible defects (old fragment boundaries) remain visible after reprocessing of the nominally purest materials. We found that the network density and glass transition temperature decrease with increasing impurity, while overall the thermal stability remains largely unaffected. The results demonstrate that hybrid CANs based on vinylogous urethane exchange chemistry can tolerate moderate monomer impurities without losing key dynamic properties, offering insights for industrial‐scale processing and material design.

Life cycle assessment (LCA) was used, next to green chemistry concepts, to compare the full environmental impacts of the epoxidation of a bio-based monomer, which can be used for the synthesis of vitrimers. On a laboratory scale, the synthesis of the monomer can either be done via a petrochemical route or via an enzymatic reaction pathway. Both reaction pathways were initially optimized to minimize the impact of suboptimal routes on the sustainability evaluation. The subsequent assessment of the enzymatic routes shows lower impact factors for most criteria compared to the petrochemical routes. A significant drawback of the enzymatic reaction, however, is its electricity consumption. The yields of the respective reactions also proved to be crucial; realistic changes in yields revealed the petrochemical reaction to be more sustainable in some cases. LCA is therefore a valuable tool for the preliminary evaluation of the developed synthesis pathways and to identify the critical adjustments needed to increase the sustainability of each reaction.

The interaction of microcroplastics (MP) with dissolved organic matter, especially humic substances, is of great importance in understanding the behavior of microplastics in aquatic ecosystems. Surface modification by humic substances plays an essential role in transport and interaction of MP with abiotic and biotic components. Previous studies on the interaction between MP and humic substances were largely based on a model compound, humic acid (Sigma-Aldrich). In our work, we therefore investigated the interaction of natural organic matter (NOM) sampled from a German surface water with low-density polyethylene particles (LDPE). High-pressure size exclusion chromatography (HPSEC) and UV/vis absorption and fluorescence spectroscopy were used to characterize the incubation solutions after modifications due to the presence of LDPE, and Raman spectroscopy was used to characterize the incubated microplastics. While the studies of the solutions generally showed only very small effects, Raman spectroscopic studies allowed clear evidence of the binding of humic fractions to MP. The comparison of the incubation of NOM and a lignite fulvic acid which also was tested further showed that specific signatures of the humic substances used could be detected by Raman spectroscopy. This provides an elegant opportunity to conduct broader studies on this issue in the future.

The influence of a defined impurity on the network characteristics of vitrimers made from an epoxidized eugenol derivative and various dicarboxylic acids is reported. One major characteristic of the monomer is the fact that it is not “clean” but rather is a mixture of the mono and diepoxidized eugenol derivatives. Mixtures like this could be thought to be representative of many technical grade compounds and the current system therefore serves as a model system to evaluate the effect of epoxide mixtures on the synthesis and the properties of the final vitrimers. The vitrimer preparation is found to be not affected by the different epoxy fractions, but in terms of the properties, there is an effect on the glass transition temperature both with the type of dicarboxylic acid but also with the level of epoxy functionalities present in the system. In spite of this, the ability of the vitrimer to perform the exchange reaction is not affected and all vitrimers can be reshaped or reprocessed showing that the processing is not affected by the changes in epoxy purity.

Silicone-based elastomers are widely in use as a housing material for composite insulators, e.g., for high-voltage outdoor applications. Especially, their outstanding hydrophobic properties make them suitable for high-voltage applications since conductive electrolytic paths on the surface that result in short circuits need to be avoided. While static hydrophobicity can be analyzed by contact-angle measurements, the analysis is more difficult for moving droplets. In this paper, we show that not only dynamic contact-angle measurements should be used to evaluate the hydrophobic properties of insulator materials, but also the occurrence of the so-called pearling effect must be considered. This effect describes the instability of accelerated drops resulting in small, pinned droplets on a material surface. We observed that occurrence of the pearling effect is dependent not only on external parameters (such as droplet volume) but also on the network density of the silicone elastomer. We have synthesized variable silicone elastomers with tunable network structures by reacting vinyl-terminated poly(dimethylsiloxane) and tetrakis(dimethylsiloxy)silane via hydrosilylation. The network properties are varied by controlling the stoichiometric balance between the monomers. The well-defined materials obtained that way allowed a careful examination of the impact of network densities (i.e., mechanical properties) and low-molecular-weight residues (sol) on the hydrophobic behavior in terms of dynamic wetting.

A new micro/mesoporous hybrid clay nanocomposite prepared from kaolinite clay, Carica papaya seeds, and ZnCl2 via calcination in an inert atmosphere is presented. Regardless of the synthesis temperature, the specific surface area of the nanocomposite material is between ≈150 and 300 m2/g. The material contains both micro- and mesopores in roughly equal amounts. X-ray diffraction, infrared spectroscopy, and solid-state nuclear magnetic resonance spectroscopy suggest the formation of several new bonds in the materials upon reaction of the precursors, thus confirming the formation of a new hybrid material. Thermogravimetric analysis/differential thermal analysis and elemental analysis confirm the presence of carbonaceous matter. The new composite is stable up to 900 °C and is an efficient adsorbent for the removal of a water micropollutant, 4-nitrophenol, and a pathogen, E. coli, from an aqueous medium, suggesting applications in water remediation are feasible.

Technological interventions aimed at addressing medication non-adherence have shown some promise but do not deliver the full potential of an Internet of Things based Adherence Decision Support (ADS) system due, in part, to a lack high-resolution definition and measure of adherence. This paper presents a novel methodology and pilot study aimed at collecting data to support an AI-based measure of adherence. The pilot study results demonstrate the viability of the methodology and that a full-scale study could provide meaningful data to support to an AI-based ADS system.

Abstract The present paper deals with the minima of conductivity in aqueous solutions, which occur due to the hydrolysis reaction with added bases. The minima show lower conductivities than the intrinsic conductivity of pure water. The minimum is a function of the molar conductivity of the added ions. There exists a limiting condition of <75.825 ⋅ 10−4 S ⋅ m2 ⋅ mol−1 for the occurrence of a minimum in the real (positive) concentration area. Values higher than 75.825 ⋅ 10−4 S ⋅ m2 ⋅ mol−1 lead to minimas in the virtual (negative) concentration area. Connecting all the minima, a curve with a maximum is observed. This point is given by 75.825 ⋅ 10−4 S ⋅ m2 ⋅ mol−1 and the intrinsic conductivity of pure water. The effect is independent of whether the added substances come from a strong or weak base. So far, the phenomenon should not influence measurements of conductivity under usual circumstances, but might be more of academic interest. Interestingly, we found that the effect for Rubidium and Cesium ions is different compared to other alkali metal ions. No minimum conductivity is predicted for these ions.

Capture and conversion of CO2 are of great importance for environment-friendly and sustainable development of human society. Poly(ionic liquid)s (PILs) combine some unique properties of ILs with those of polymers and are versatile materials for CO2 utilization. In this contribution, we briefly outline innovative PILs emerged over the past few years, such as polytriazoliums, deep eutectic monomer-based PILs, and polyurethane PILs. Additionally, we discuss their advantages and challenges as materials for carbon capture and storage and the fixation of CO2 into useful materials.

The State Composer Algorithm enables a Level-Shifted PWM Modulator to achieve an equal power distribution among the cells of a Cascaded Multicell converter (or similar). This paper reports the implementation and validation of a LS-PWM modulator based on a State Composer Algorithm for a Medium Frequency Railway Traction Converter, supporting up to 10 cells. The results were obtained using a Real Time Simulator.

Narrow-dispersed and nanoporous poly(melamine-formaldehyde) particles were prepared by aqueous dispersion polymerization using silica particles as template. The synthesis parameters were optimized towards uniform particles sizes and ideal template performance toward high surface areas. Nitrogen sorption measurements confirmed the 12 nm sized mesopores and a specific surface area of up to 400 m(2) g(-1). The particles sizes and the template distribution were investigated by SEM, TEM, and laser diffraction measurements. The particles were investigated for their oxyanion adsorption properties in dependency of the pH in the water. The preliminary results obtained from the adsorption experiments make nanoporous poly(melamine-formaldehyde) particles a promising candidate for the capture of oxyanions and potentially also for other ions in waste water.

Polymeric outdoor insulation material provides the properties of hydrophobicity, which has an important effect on the functionality in the application. The retention of the hydrophobicity depends on various factors, whereby the combined electric and electrolytic stress is close to the application. In this paper, all of the investigations are focused on silicones. The retention and the recovery of the hydrophobicity is provided by different processes. One of them is attributed to the low molecular weight (LMW) contents of the silicones. For this reason, the retention of the hydrophobicity behavior after different chemical treatments is evaluated. For the measurement of the retention of the hydrophobicity the Dynamic Drop Test (DDT) is used. The DDT has proven to be a suitable test method and the investigations are intended to improve the test with respect to repeatability and reproducibility. In this paper, after a short introduction to the topic, the investigation process is described, the measuring setup and the measurement results are shown and discussed.

Mesoporous poly(melamine-formaldehyde) (MF) particles with surface areas of up to 200m2g−1 were synthesized by an inverse emulsion polymerization using dodecane and Span80® as continuous phase. The finer details of the shape control (using emulsion techniques) and the porosity control (using silica nanoparticles as hard-template) are discussed. The impact of phase-separation processes on the observable porosity of the 20–200µm sized spherical particles is analysed by gas sorption methods and electron microscopy. The high density of amine and triazine functional groups in the porous MF particles make the material a promising adsorber for heavy metal ions and methylene blue. In a preliminary column experiment, the synthesized material exhibited a total capacity of 2.54mmol/g (≙ 812.4mg/g) for the adsorption of methylene blue.

This paper describes briefly the modeling of the modular multilevel converter, which was introduced by Rainer Marquardt [1]. The mathematical model is used to calculate the average losses and junction temperature of the semiconductor devices in dependence on the converter output power. The junction temperature, the semiconductor losses and their several components are shown in order to compare a converter with IGCTs and a converter with IGBTs as switches. The comparison is made to show in which operating point the one or the other has its advantages.

The design and synthesis of novel microporous. materials have received tremendous attention in both CO2 storage and sequestration (CSS) and electrochemical energy storage (EES). We report molecular design and synthesis of conjugated :microporous polycarbazole networks as new precursors for nitrogen-enriched porous carbons. As-prepared porous carbons exhibit a high nitrogen content (6.1 wt %), ulttamicropore size (0.7-1 nm), and large surface area (1280 m(3) g(-1)). As a result, these novel nitrogen-enriched carbons show highly efficient, and reversible CO2 capture (can store 20.4 wt % at I. bar and 11.1 wt % at 0:15 bar and at 273 K, while maintaining 100% CO2 uptake capacity after five cycles). Moreover, they can be applied as electrodes and enable high-performance EES devices with a fast charge/discharge rate (8 s), high electrochemical capacity (558 F g(-1)), and good cycle ability (retain 95% capacity after 1000 cycles).

Porous polyimides were synthesized fast and easily in water by combining the hydrothermal synthesis with the use of an amphiphilic block copolymer, Pluronic F-127 (HT-PF method) and were fully characterized. Their properties were compared with those of polyimides with the same chemical structure synthesized using m-cresol as solvent and isoquinoline as catalyst. Two of the polyimides synthesized by the HT-PF method were used as supports to obtain heterogenized palladium or iron catalysts (Pd-(HT-PF), Fe-(HT-PF); both metal-polyimides showed good catalytic activity Suzuki CC coupling reactions and alkylation of amines with alcohols, respectively without metal leaching detected during the reaction.

The effective and safe capture and storage of radioactive iodine (I or I) is of significant importance during nuclear waste storage and nuclear energy generation. Here we present detailed evidence of highly efficient and reversible iodine capture in hexaphenylbenzene-based conjugated microporous polymers (HCMPs), synthesized via Buchwald−Hartwig (BH) cross-coupling of a hexakis(4-bromophenyl)benzene (HBB) core and aryl diamine linkers. The HCMPs present moderate surface areas up to 430 m g−1, with narrow pore size distribution and uniform ultramicropore sizes of less than 1 nm. Porous properties are controlled by the strut lengths and rigidities of linkers, while porosity and uptake properties can be tuned by changing the oxidation state of the HCMPs. The presence of a high number of amine functional groups combined with microporosity provides the HCMPs with extremely high iodine affinity with uptake capacities up to 336 wt %, which is to the best of our knowledge the highest reported to date. Two ways to release the adsorbed iodine were explored: either slow release into ethanol or quick release upon heating (with a high degree of control). Spectral studies indicate that the combination of microporosity, amine functionality, and abundant π-electrons ensured well-defined host−guest interactions and controlled uptake of iodine. In addition, the HCMPs could be recycled while maintaining 90% iodine uptake capacity (up to 295%). We envisage wider application of these materials in the facile uptake and removal of unwanted oxidants from the environment.

The effective and safe capture and storage of radioactive iodine (1291 or 1311) is of significant importance during nuclear waste storage and nuclear energy generation. Here we present detailed evidence of highly efficient and reversible iodine capture in hexaphenylbenzene-based conjugated microporous polymers (HCMPs), synthesized via Buchwald-Hartwig (BH) cross-coupling of a hexakis(4-bromophenyl)benzene (HBB) core and aryl diamine linkers. The HCMPs present moderate surface areas up to 430 m(2) g(-1), with narrow pore size distribution and uniform ultramicropore sizes of less than 1 nm. Porous properties are controlled by the strut lengths and rigidities of linkers, while porosity and uptake properties can be tuned by changing the oxidation state of the HCMPs. The presence of a high number of amine functional groups combined with microporosity provides the HCMPs with extremely high iodine affinity with uptake capacities up to 336 wt %, which is to the best of our knowledge the highest reported to date. Two ways to release the adsorbed iodine were explored: either slow release into ethanol or quick release upon heating (with a high degree of control). Spectral studies indicate that the combination of microporosity, amine functionality, and abundant pi-electrons ensured well-defined host-guest interactions and controlled uptake of iodine. In addition, the HCMPs could be recycled while maintaining 90% iodine uptake capacity (up to 295%). We envisage wider application of these materials in the facile uptake and removal of unwanted oxidants from the environment.

Although, current preparation methods for microporous organic polymers (MOP) based on coupling or condensations reactions are simple and flexible, they suffer from the requirement of additional modification steps for introducing properties for specific purposes. In the present work, we have developed a simple and rapid synthetic strategy to prepare MOP possessing reactive sites to incorporate any molecules of interest by “Click Chemistry”. The clickable MOP with high surface area was readily synthesized through Schiff base chemistry using propargylated anthraquinone and melamine in the catalyst free, one-pot process. The versatility of the click coupling on the acetylene functional MOP was demonstrated on a model reaction using independently prepared fluorescent azido-pyrene.