ABSTRACT The versatility of vat photopolymerization additive manufactured (VPAM) elastomers garners much interest in the production of medical supplies and microfluidic devices. However, little research has characterized the liquid barrier properties and chemical resistance specifically related to these emerging acrylate‐based VPAM polymers. Herein, we describe a systematic approach to studying the structure–property relationships for a series of 3D printable elastomers from commonly used monomers and crosslinkers, including n‐butyl acrylate (BA) and 2‐hydroxyethyl acrylate (HEA). Polymer samples showed elongations‐to‐break between 200%–400% and Young's moduli between 0.4–0.6 MPa. The study helps to develop a picture of the chemical space inhabited by these model systems via permeability experiments and relation to Hansen solubility parameters (HSPs). The permeability of the tested solvents dimethyl sulfoxide (DMSO), dimethylformamide (DMF), pyridine, isopropanol (IPA), and tetrahydrofuran (THF) was related to the composition and increased water uptake of the materials. As the weight percent of HEA increased in the polymer composition, the permeability of all solvents increased. The magnitude of the permeability depended on solvent interactions with water, quantified by HSPs, and was independent of polymer composition. THF exhibited the highest permeability through the polymer membranes due to its low HSP. The formulated elastomers represent modular VPAM materials accessible with current commercial 3D printing technology that can be deployed for specific applications.

Bipolar membranes (BPMs) are increasingly recognized as a promising electrolyte option for water electrolysis, attributable to their distinctive properties derived from the membrane's layered structure, which consists of an anion exchange (AEL) and a cation exchange layer (CEL). This study investigates four different BPMs and the influence they have on the performance of a water electrolysis cell under two different feed configurations: (1) a symmetric deionized water feed to both anode and cathode compartments and (2) an asymmetric feed with a 0.5 mol/L NaCl catholyte feed and a deionized water anolyte feed. The BPMs were also investigated for total chlorine (Cl) species (e.g., Cl-, Cl2, HOCl, and ClO-) in the anolyte due to Cl- crossover from the catholyte during water electrolysis with the asymmetric feed, at an applied current density of 250 mA/cm2. The best-performing BPM with the asymmetric feed was an E98-05 (CEL)/FAS-50 (AEL) membrane with a TiO2 water dissociation catalyst at the BPM junction. This membrane had the lowest measured Cl species crossover and lowest cell voltage at a given current density under asymmetric conditions compared to the other BPMs studied. It was also found that under asymmetric conditions the CEL facing the catholyte feed determined the amount of total Cl species crossover due to anion exclusion (Donnan exclusion) of the CEL, reducing the amount of Cl- in the CEL where it crossed over to the AEL and the anolyte compartment.

This work presents the assembly of 48 papers, representing 74 different compounds and blends, into a machine-readable database of nonaqueous proton-conducting materials. SMILES was used to encode the chemical structures of the molecules, and we tabulated the reported proton conductivity, proton diffusion coefficient, and material composition for a total of 3152 data points. The data spans a broad range of temperatures ranging from -70 to 260 °C. To explore this landscape of nonaqueous proton conductors, DFT was used to calculate the proton affinity of 18 unique proton carriers. The results were then compared to the activation energy derived from fitting experimental data to the Arrhenius equation. It was found that while the widely recognized positive correlation between the activation energy and proton affinity may hold among closely related molecules, this correlation does not necessarily apply across a broader range of molecules. This work serves as an example of the potential analyses that can be conducted using literature data combined with emerging research tools in computation and data science to address specific materials design problems.

Additive manufacturing (AM), known as three-dimensional (3D) printing, uses computer-controlled materials deposition to fabricate 3D objects by selectively depositing materials, usually in a layer-wised fashion, to build a 3D object using free-form fabrication. Integrating silicone elastomers with AM deposition strategies has been of interest due to the important application characteristics of silicones such as excellent mechanical properties, thermal resistance, and chemical inertness. This work presents a study on the shear-thinning properties of thermally-curable liquid silicone feedstocks to describe ideal flow and shape-retention properties for direct ink writing of liquid silicone rubbers. To complement the direct ink writing process developed in this work for silicone AM, flow properties of various silicone feedstocks were identified through measurement of rheological properties using the AM fluid dispenser under various pressures, supported by parallel plate oscillatory shear rheology. A systematic process for evaluating and investigating the AM performance of seven different grades of silicones is introduced. The shape retention, overhang, and dimensional accuracy of these silicones in 3D printing process have been compared and summarized. This systematic evaluation methodology can be applied for silicone material selection and printing of silicone parts with complicated architectures.

Growing concerns regarding clean water scarcity have spurred significant interest in desalination technologies. While reverse osmosis membranes can efficiently remove salt and impurities, they typically consume high amounts of electrical energy due to their reliance on applied pressure. Moreover, conventional flat membranes often face issues such as fouling that leads to performance deterioration in the desalination process. Here, we report a 3D-structured advanced layered nanocomposites (ALN) aerogel for continuous desalination powered by solar energy (i.e., without requiring electrical energy, as is required by pressure-driven membrane desalination). This ALN incorporates hydrothermally synthesized LDH@MXene, and in combination with the TEMPO-mediated oxidation of delignified biomass (TODB), the ALN showcases exceptional photothermal performance (reaching temperatures of 85 degrees C) under sunlight irradiation (1 kWm- 2). This performance, which is superior to that achieved by other MXene-based SE, can be attributed to its high surface area and UV-Vis-NIR absorption capacity, and it ultimately results in a high water evaporation rate. Further, the internal aligned channels, which are fabricated through freeze-casting, play a crucial role in preventing salt crystallization, and they therefore enhance the continuous desalination performance of the system. Our findings ultimately suggest that ALN aerogels with controllable aligned channels represents a promising energy-efficient and sustainable alternative for clean water production.

Bipolar membranes (BPMs) are a unique construction of ion exchange membranes with anion exchange and cation exchange layers in series. Due to the unique transport processes in BPMs, they are becoming an increasingly attractive option for many electrochemical devices, especially in water electrolysis and carbon dioxide reduction. However, because a large number of anion and cation exchange membranes are available, it can be difficult to select the layers for BPM fabrication, particularly when targeting specific properties for use in a device. In this study, a survey of nine anion and nine cation exchange membranes was conducted to assess their steady-state ion transport properties. The primary application of this work is seawater electrolysis; therefore, measurements of salt flux and area resistance in 0.5 mol/L sodium chloride solutions were performed. These measurements displayed a trade-off behavior, with membranes displaying higher area resistance and having a lower salt flux. Conversely, membranes with lower area resistance had a higher salt flux. From these individual membrane results, a methodology was formulated to select component membranes for BPM fabrication, primarily considering their transport characteristics. Three BPMs were fabricated using this methodology. A model was developed to integrate the parameters and ion transport properties measured from individual membranes to predict salt flux and area resistance values for a BPM. Values produced from the model were then compared with experimental salt flux and area resistance BPM measurements. Both the model and experimental salt flux and area resistance BPMs exhibited an area resistance-flux trade-off, like that of the component membranes.

Proton exchange membranes (PEMs) with high conductivity are of critical importance for the development of fuel cells, electrolyzers, and other electrochemical technologies. In this research, poly(1,1,2,2-tetrafluoro-2-phenoxyethane-1-sulfonic acid) (PTPS) with an aromatic polymer main chain and a perfluorinated superacidic polymer side chain was synthesized. The water dynamics of PTPS were characterized across various length scales using a combination of Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) and compared with Nafion, a standard perfluorinated PEM, and sulfonated poly(ether sulfone) (SPES 40), an aromatic PEM without perfluorinated superacid side chains. The T 1 and T 2 relaxation times of water in the samples probed by NMR increase from SPES 40 to PTPS to Nafion, indicating that the local motion of the water molecules becomes faster. This trend corresponds well with the relative fraction of bulk-like water determined using FTIR. At larger length scales, the diffusion coefficient of water was characterized using pulsed-field gradient NMR (PFG-NMR). At a longer diffusion time (Δ = 100 ms), PTPS has a smaller diffusion coefficient compared with both Nafion and SPES 40, due to restricted diffusion, and this effect is also evident in the proton conductivity of the hydrated membranes. From this comparison, it is apparent that the aromatic backbone and side chain type greatly influence the water dynamics in PEMs at various length scales and the water dynamics significantly impact the bulk proton conductivity. These insights will lead to new designs for aromatic PEMs and help to identify bottlenecks in current materials.

Hydrogen gas evolution using an impure or saline water feed is a promising strategy to reduce overall energy consumption and investment costs for on-site, large-scale production using renewable energy sources. The chlorine evolution reaction is one of the biggest concerns in hydrogen evolution with impure water feeds. The "alkaline design criterion" in impure water electrolysis was examined here because water oxidation catalysts can exhibit a larger kinetic overpotential without interfering chlorine chemistry under alkaline conditions. Here, we demonstrated that relatively inexpensive thin-film composite (TFC) membranes, currently used for high-pressure reverse osmosis (RO) desalination applications, can have much higher rejection of Cl- (total crossover of 2.9 ± 0.9 mmol) than an anion-exchange membrane (AEM) (51.8 ± 2.3 mmol) with electrolytes of 0.5 M KOH for the anolyte and 0.5 M NaCl for the catholyte with a constant current (100 mA/cm2 for 20 h). The membrane resistances, which were similar for the TFC membrane and the AEM based on electrochemical impedance spectroscopy (EIS) and Ohm's law methods, could be further reduced by increasing the electrolyte concentration or removal of the structural polyester supporting layer (TFC-no PET). TFC membranes could enable pressurized gas production, as this membrane was demonstrated to be mechanically stable with no change in permeate flux at 35 bar. These results show that TFC membranes provide a novel pathway for producing green hydrogen with a saline water feed at elevated pressures compared to systems using AEMs or porous diaphragms.

Additive manufacturing (AM) is a disruptive manufacturing process that gives designers freedom to create highly complex shapes through free-form fabrication. The majority of polymers used in extrusion AM are thermoplastics because they are easy to process in affordable machines. While there are a number of moderate modulus thermoplastics in regular use in AM, thermoplastics are known to weaken with increases in temperature or exposure to solvents and many commodity thermoplastics used in AM are brittle. On the other hand, there are few elastomers, and even fewer elastomer reinforcement schemes, that are accessible using standard AM technologies. In this work, we report a novel dual extrusion process that integrates elastomeric silicone with reinforcing thermoplastic. By developing and demonstrating a dual extrusion 3D printer that can process common thermoplastics with commercially available thermosetting silicones, new types of composite elastomers are reported with good mechanical performance. The 0(degrees)/20(degrees)/-20(degrees) grid pattern thermoplastic reinforced samples achieved 2.5 MPa tensile strength in low extension region (0.5 strain), which improves the initial stiffness of the composite component. Desired mechanical responses of composite structures can be realized by tuning the reinforcement volume ratio and infill percentages, and applying various types of reinforcement mesh patterns and thermoplastics.Highlights A dual extrusion process integrates fus filament fabrication and direct ink writing technologies. Thermoplastic reinforced silicone composite with stiff/soft properties. Tunable volume ratio, infill percentage, mesh pattern, and material option.

A survey of 23 commercially available cation exchange membranes was performed for the downselection of membranes for use in a polysulfide-permanganate redox flow battery (pS-Mn RFB). The survey measured the flux of permanganate ions across a 0.1 mol L−1 concentration gradient as well as the membrane resistance in a 0.5 mol L−1 sodium chloride solution. The membranes exhibited the characteristic flux/resistance trade-off observed in most classes of membranes. To connect the individual membrane testing to how the membranes will perform in a device, cell performance data in a pS-Mn RFB was collected for three membranes from the survey. The coulombic, voltaic, and energy efficiency at low cycle counts aligned with the predictions from the membrane flux and resistance survey results. The study also identified three membranes—Fumapem F-930-RFS, Fumapem FS-715-RFS, and Aquivion E98-09S—that outperformed most other membranes regarding their position on the flux-resistance trade-off curve, indicating them to be good candidates for further testing.

The design of small molecules is crucial for technological applications ranging from drug discovery to energy storage. Due to the vast design space available to modern synthetic chemistry, the community has increasingly sought to use data-driven and machine learning approaches to navigate this space. Although generative machine learning methods have recently shown potential for computational molecular design, their use is hindered by complex training procedures, and they often fail to generate valid and unique molecules. In this context, pre-trained Large Language Models (LLMs) have emerged as potential tools for molecular design, as they appear to be capable of creating and modifying molecules based on simple instructions provided through natural language prompts. In this work, we show that the Claude 3 Opus LLM can read, write, and modify molecules according to prompts, with an impressive 97% valid and unique molecules. By quantifying these modifications in a low-dimensional latent space, we systematically evaluate the model’s behavior under different prompting conditions. Notably, the model is able to perform guided molecular generation when asked to manipulate the electronic structure of molecules using simple, natural-language prompts. Our findings highlight the potential of LLMs as powerful and versatile molecular design engines.

Azole molecules are investigated as potential candidates for proton conductors under anhydrous conditions. Since 1,2,3-triazole has the lowest melting point (T m = 17 degrees C), it was blended with three phosphonic acid-containing molecules (small molecules with one and two phosphonic acids per molecule and a phosphonic acid polymer) to provide a source of excess protons to enhance the proton conductivity of the blends. We study a wide range of compositions in each system to find that these three mixtures show a maximum proton conductivity at moderate doping compositions, approximately 5-10 azole molecules per phosphonic acid group. Using NMR diffusometry, we show that the protons bonded to nitrogen move faster than the protons bonded to carbons of 1,2,3-triazole, suggesting proton hopping between azole proton carriers. Given the high proton conductivity at 90 degrees C of the best mixtures, in the range of 20-60 mS/cm, this work provides a path forward for future work in anhydrous proton-conducting polymer membranes. Additionally, Raman spectroscopy was used to accurately determine the molar percentage of protonated 1,2,3-triazole. Combining that with the proton diffusion results, we find that the phosphonic acid polymer shows the most proton hopping at low acid content.

Increasing the internal light extraction efficiency of organic light-emitting diodes (OLEDs) is key to improving their performance for solid-state lighting applications; however, it is challenging to do this in a way that is compatible with high volume manufacturing. Here, it is shown that the outcoupling efficiency of OLEDs can be improved by diluting their hole transport layer (HTL) with the low refractive index material trifluoropropyl oligomeric silsesquioxane (F-POSS). Specifically, co-evaporating 40 vol.% F-POSS in the HTL of single and multi-stack phosphorescent OLEDs decreases its refractive index by Delta n approximate to 0.2, which in turn yields a approximate to 12% increase in their outcoupling efficiency with no impact on electrical performance or operational lifetime. This result is significant because F-POSS is a small molecule that sublimes cleanly, does not aggregate, and is compatible with state-of-the-art HTL materials, making it a realistic path to increase light extraction in commercial OLEDs manufactured on existing production lines. Co-evaporating a low refractive index small molecule in the hole transport layer of organic light-emitting diodes is shown to increase their light extraction efficiency without sacrificing electrical performance or operational lifetime.image

Bipolar membranes (BPMs) are asymmetric, layered ion exchange membranes that are increasingly being explored for use in electrochemical devices. This study aims to investigate the effect that the direction of a diffusive driving force across a salt solution concentration gradient has on the flux through a BPM due to its asymmetric nature. BPMs were fabricated using PiperION poly(aryl piperidinium) A40 as the anion exchange layer (AEL) and Nafion 212 as the cation exchange layer (CEL) with no interfacial junction catalyst. The permeability of sodium chloride through the BPM membranes was measured across a 0.5molL-1 concentration differential for both orientations of the membrane, e.g. AEL facing the 0.5molL-1 NaCl solution versus the CEL facing the 0.5molL-1 NaCl solution. A flux differential of (76.3 ± 4.8)% was measured for the BPM depending on the direction of the driving force. A model based on Fick’s law and the Donnan equilibrium was developed and used to show that the flux differential results from changes in the ionic environment at the AEL–CEL junction due to differences in the ion diffusion coefficients and fixed charge concentrations of the two layers.

Low-temperature heat (T<130 degrees C) can be utilized by thermally regenerative batteries (TRBs) for power production, allowing the thermal energy to be converted to storable chemical potential energy. However, TRBs suffer from high ohmic losses and ammonia crossover, which has slowed their development. In this study, we examined how the use of six different membranes influenced TRB performance, determined the most influential membrane parameters, and identified promising membrane candidates that cost-effectively increase TRB performance. Of the six membranes examined, an inexpensive, hydrocarbon CEM (Selemion CMVN) had low ammonia crossover without compromising resistance, resulting in good performance across all metrics studied. A thin anion exchange membrane (Sustainion, 50 microns) showed a high peak power density of 82 mW cm(-2) due to low resistance, but the average power density and energy density were low due to high ammonia flux. Full discharge curves using Selemion CMVN provided an average power density of 26 +/- 7 mW cm(-2) with an energy density of 2.9 Wh L-1, which were large improvements on previous TRBs. A techno-economic analysis showed that Selemion CMVN had the lowest levelized cost of storage ($410 per MWh) at an applied current density of 50 mA cm(-2).

Vat photopolymerization (VP), or stereolithography, is rapidly being adopted as an additive manufacturing (AM) technique that yields parts with high precision and feature sizes below 100 mu m. As such, the development of materials for VP is essential for extending this printing technology into a variety of application spaces. In this work, we describe a thermoset acrylate polymer system suitable for fabricating sophisticated parts via vat polymerization (VP) with excellent strength (E = 1500 MPa) and toughness (strain to break = 13%-46%). The printed parts can be formulated to be completely water-soluble for cavity molding applications. While the material does not dissolve in neutral or acidic aqueous conditions, it rapidly dissolves in the presence of base, a property afforded by using methacrylic anhydride as a hydrolytically cleavable cross-linker. Additionally, adjustment of the monomer ratio and cross-linker content in the resin formulation tunes the mechanical properties of the printed polymer. The resulting material is readily processed with vat polymerization additive manufacturing techniques, allowing for direct and rapid construction of intricate and complex parts for applications such as tissue engineering or lost-wax casting.

Redox flow batteries (RFBs), a promising technology for large-scale power grid energy storage, utilize a membrane separator to facilitate an ionic current while preventing mixing of the anolyte and catholyte solutions. The anolyte and catholyte of an RFB each contain an electroactive species, and usually an additional supporting electrolyte to charge balance the anode and cathode redox reactions and reduce overall ohmic losses. This study investigates the impact of the supporting electrolyte concentration and composition on Nafion’s transport properties using permanganate as the permeant. The permanganate concentration was kept constant at 0.1m, while sodium chloride and sodium hydroxide were both studied as supporting electrolytes. The sodium chloride concentration was varied from 0.1m to 4.0m, while the sodium hydroxide concentration was varied from 0.1m to 10m. The permanganate permeability, water sorption coefficient, and salt sorption coefficients were measured for Nafion, with a peak permeability being observed at a supporting electrolyte concentration of 1m for both electrolytes. A framework to describe the observed behavior was derived using first principles to determine the transport coefficients under these conditions. It was found that at low concentrations, the permanganate permeability is controlled by Donnan exclusion and salt sorption, while at high concentrations it is controlled by salt diffusion and osmotic deswelling.

pH-responsive ion exchange membranes were developed by photoinitiated free radical polymerization of a resin formulation containing poly(ethylene glycol diacrylate) and diurethane dimethacrylate oligomers, dipentaerythritol penta-/hexa-acrylate cross-linker, photoinitiators, and acrylic acid as a stimuli-responsive monomer. The membranes were switched from their protonated, nonconductive state to a deprotonated, ion-conductive state by modulating the pH of the storage solution. This process was analyzed by monitoring the membrane transport properties (ionic resistance and permselectivity) and the water uptake in the different states. It was observed that upon deprotonation at high pH, the higher ionicity of the membrane allowed for cation conduction, which was confirmed by observing a substantial decrease in the area specific resistance of the membrane. The ionic resistance decreased 5 orders of magnitude, from 9.86 +/- 0.52 Omega m(2) to 3.54 x 10(-4) +/- 7.78 x 10(-5) Omega m(2) for a sample with 15 wt % acrylic acid. The increased ionicity of the membrane increased the hydrophilicity of the samples, which was confirmed by observing a higher water uptake for the membranes in their deprotonated state. Additionally, the higher ionicity of the membrane increased the membrane's exclusion of co-ions, as described by the Donnan principle. This phenomenon translated into a higher permselectivity of the membranes in their deprotonated state, which increased from between 0.25 +/- 0.03 and 0.57 +/- 0.02 to values between 0.76 +/- 0.01 and 0.86 +/- 0.01. The chemical stability and reversibility of these stimuli-responsive membranes were analyzed by cycling a membrane sample between its protonated and deprotonated states for ten cycles and monitoring the membrane ionic resistance and permselectivity values. It was observed that permselectivity varied between 0.32 +/- 0.03 and 0.88 +/- 0.01; however, the area specific resistance of the membrane in its protonated state decreased asymptotically with increasing cycle number until it reached a plateau in cycle numbers 5 to 10, likely due to irreversible water swelling.