Hydration of alkali and alkaline-earth montmorillonites: an experimental comparative study from X-ray diffraction, water sorption isotherms and mid-infrared spectroscopy

Multiblock poly(arylene ether sulfone) copolymers are attractive for polyelectrolyte membrane fuel cell applications due to their reportedly improved proton conductivity under partially hydrated conditions and better mechanical/thermal stability compared to Nafion. However, the long hydrophilic sequences required to achieve high conductivity usually lead to excessive water uptake and swelling, which degrade membrane dimensional stability. Herein, we report a fundamentally new approach to address this grand challenge by introducing shape-persistent triptycene units into the hydrophobic sequences of multiblock copolymers, which induce strong supramolecular chain-threading and interlocking interactions that effectively suppress water swelling. Consequently, unlike previously reported multiblock copolymer systems, the water swelling of the triptycene-containing multiblock copolymers did not increase proportionally with water uptake. This combination of high water uptake and low swelling behavior of these copolymers resulted in excellent proton conductivity and membrane dimensional stability under fully hydrated conditions. In particular, the triptycene-containing multiblock copolymer film with the longest hydrophilic block length (i.e., BPSH100-TRP0-15k-15k) had a water uptake of 105%, an excellent proton conductivity of 0.150 S/cm, and a volume swelling ratio of just 29% (more than 42% reduction compared to Nafion 212).

Ion exchange membranes are a crucial component of energy conversion and storage devices (such as fuel cells, batteries, electrolyzers), and their transport properties are associated with cation and water interaction. Despite the significant development of robust membranes for decades, the effect of various monovalent and divalent cations on cell performance and durability has not been well explored. In this study, various monovalent and divalent cations were exchanged with two different commercially available cationic exchange membranes, namely N117 (Nafion 117) and PBC (1.0) (Penta Block Copolymers). The membranes showed significant changes in elasticity and plasticity based on cation form and hydration state. Lower young’s modulus of the wet form than that of their respective dry forms may be attributed to swelling caused by water uptake, which disrupts the interaction between the metal counterions and the sulfonate groups of the membrane. On the other hand, the proton conductivity exhibited a similar trend for both types of membrane for three different temperatures. The conductivity of divalent forms showed more than one order of change in magnitude compared to the protonated membranes, and the conductivity of all cation forms of membranes increased with temperature. The decrease in the conductivity with cations may be attributed to the disruption of the ion transport mechanism within the membrane due to stronger interaction with divalent ions. However, the water uptake study doesn’t significantly change with the ion forms except PBC-Li+, which shows the highest water uptake of 42.04% compared to all other cation forms. Thus the conductivity mainly depends on the ionic interaction between various cation and sulfonate groups of the membrane rather than the water content. Finally, the effect of various monovalent and divalent ions on the morphological transitions will be investigated in the future.

Improving porosity and water uptake of aluminum metal-organic frameworks (Al-MOFs) as graphite oxide (GO) composites

The primary cause of wellbore instability is the interaction of water-based muds with shales. The movement of water and ions into or out of a shale can result in large changes in pore pressure in the vicinity of the wellbore, potentially leading to wellbore failure. A new method, the Gravimetric – Swelling Test (GST), for determining the compatibility between shales and drilling fluids is presented in this paper. An experimental protocol and equations are presented that describe how such measurements can be conducted and interpreted with relative ease. The mass of water and ions entering or leaving shale samples is determined. With additional swelling measurements, the impact of the water and ions uptake on swelling pressures generated can also be obtained. In this paper, results are presented for two preserved shale samples obtained from the field. The influence of different types of ionic solutions on water and ion movement is presented for each shale. It is shown that water uptake and swelling of shales is controlled not only by differences between shale water activity and water activity in the mud (as assumed in the past), but ion type and concentration also play an important role. In these tests the water uptake decreases, while the ion adsorption increases with increasing salt concentration. Different types of cations are shown to have a large influence on water/ion movement. This paper presents a data set showing the influence of ion type and concentration on water uptake by shales. The role of capillary pressure, osmotic effects and ionic diffusion on swelling behavior of shales is also discussed. The technique presented herein may possibly be used at the rig-floor to determine the compatibility of shales with salt-water drilling fluids.

Water sorption isotherms of gel-type Dowex 50WX4 and Dowex 50WX8 and macroreticular Amberlyst-15 resins in H+, Na+, and alkaline earth metal ionic forms have been determined at 298 ± 1 K using the isopiestic technique. The hydration numbers of cations derived from the analysis of the water sorption isotherms using the D'Arcy and Watt equation compare well with those reported for similar types of ion exchangers obtained using other techniques. An interesting feature that has emerged from the analysis is the presence of a constant amount of water having bulk structure in Amberlyst-15, irrespective of the nature of the cations, possibly those filling the pores of the exchanger. The present study, thus, indicates the structural differences between the water present in the gel phase and in the pores of the macroreticular Amberlyst-15.

The functional behaviour of tablets is strongly influenced by their manufacturing process and the choice of excipients. Water uptake and swelling are prerequisites for tablet disintegration, dispersion and hence active pharmaceutical ingredient (API) dissolution. High proportions of polymeric excipients in tablets, which are typically used as API carriers in amorphous solid dispersions (ASDs), may be challenging due to the formation of a gelling polymer network (GPN). In this study, systematic investigations into the formulation development of tablets containing polymeric and other excipients are performed by water uptake and swelling analysis. The impact of tablet composition and porosity as well as pH of the test medium are investigated. The pH affects the analysis results for Eudragit L100–55 and Eudragit EPO. HPMC and Kollidon VA64 inhibit water uptake and swelling of tablets due to the formation of a GPN. High tablet porosity, coarse particle size of the polymer and the addition of fillers and disintegrants can reduce the negative impact of a GPN on tablet performance. The application of lubricants slows down the analysed processes. Water uptake and swelling data are fitted to an empirical model obtaining four characteristic parameters to facilitate the simple quantitative assessment of varying tablet formulations and structural properties.

With clean energy technology unable to support increasing global energy demand, CO2 emissions rise annually with continued fossil fuel usage.1 Electrochemical devices such as fuel cells and electrolysers provide a promising solution in conjunction with current renewable technologies. The current standard of these materials is Nafion, which has good performance, but is prepared with controlled fluorinated substances, limiting synthesis routes and access, as well as producing toxic degradation products.2this research focuses on development of a fluorine free, hydrocarbon PEM with performance exceeding or comparable to current fluorinated materials. Sulpho-phenylated polyphenylene polymers have previously exhibited properties comparable to PFSA counterparts.3 These materials, however, posses high water uptake and swelling, limiting performance and durability in electrochemical devices. By incorporating polyphenyl linker molecules of various conformations and sizes to form copolymers, structure-property relationships can be explored. These copolymers will be synthesized by a facile Diels-alder polymerization method, incorporating the linker molecules in varying ratios. The resulting copolymers, verified by NMR, will be casted into membranes, and explored by various characterization methods. The mechanical strength, water uptake and swelling, and ion exchange capacity will be evaluated, determining the structure-property relationships that can predict its behavior in an electrochemical device. Specific tunability of the polymer’s properties allows for the fabrication of optimal PEM materials, characterised by reduced water uptake and swelling, which in turn improves electrochemical performance and durability. These advancements represent promising steps toward a green energy-based economy.(1) World Energy Outlook 2024 – Analysis. IEA. https://www.iea.org/reports/world-energy-outlook-2024 (accessed 2024-12-08).(2) Feng, M.; Qu, R.; Wei, Z.; Wang, L.; Sun, P.; Wang, Z. Characterization of the Thermolysis Products of Nafion Membrane: A Potential Source of Perfluorinated Compounds in the Environment. Sci Rep 2015, 5 (1), 9859. https://doi.org/10.1038/srep09859.(3) Adamski, M.; Peressin, N.; Holdcroft, S. On the Evolution of Sulfonated Polyphenylenes as Proton Exchange Membranes for Fuel Cells. Materials Advances 2021, 2 (15), 4966–5005. https://doi.org/10.1039/D1MA00511A.

Carboxylated polysulfone (CPS), poly (1,4-phenylene ether ethersulfone) (PPEES), membranes were prepared and used for the separation of NaCl and <TEX>$CaCl_2$</TEX>, in efficient way with less energy consumption. In this work, nanofiltration and reverse osmosis membranes were employed to the salt rejection behavior of the different salt solutions. The influence of applied pressure (1-12 bar), on the membrane performance was assessed. In CM series of membranes, <TEX>$CM_1$</TEX> showed maximum of 97% water uptake and 36% water swelling, whereas, <TEX>$CM_4$</TEX> showed 75% water uptake and 28% water swelling. In RCM series, <TEX>$RCM_1$</TEX> showed 85% water uptake and 32% water swelling whereas, in <TEX>$RCM_4$</TEX> it was 68% for water uptake and 20% for water swelling. Conclusively reverse osmosis membranes gave better rejection whereas nanofiltration membrane showed enhanced flux. CM1 showed 58% of rejection with 12 L/(<TEX>$m^2$</TEX> h) flux and <TEX>$RCM_1$</TEX> showed 55% of rejection with 15 L/(<TEX>$m^2$</TEX> h) flux for 0.1 wt.% NaCl solution. Whereas, in 0.1 wt.% <TEX>$CaCl_2$</TEX> solution, membrane <TEX>$CM_1$</TEX> showed 78% of rejection with 12 L/(<TEX>$m^2$</TEX> h) flux and <TEX>$RCM_1$</TEX> showed 63% rejection with flux of 9 L/(<TEX>$m^2$</TEX> h).

Gelatin composite films were prepared from gelatin solutions (10% w/v) containing multi-walled carbon nanotubes (MWCNT, 0.5, 1, 1.5, and 2% w/w gelatin) as nanofiller. The water solubility, water swelling, water uptake, water vapor permeability (WVP), mechanical, and antibacterial properties of the films were examined. Water solubility, water swelling, water uptake, and WVP for gelatin films were 45 ± 1%, 821 ± 42%, 45 ± 1.1%, and 0.4 ± 0.022 g mm/m2 kPa h, respectively. Incorporation of MWCNT caused a significant decrease in water solubility, water swelling, water uptake, and WVP. Gelatin/MWCNT films containing 1–1.5% MWCNT showed the lowest water vapor transmission. Tensile strength, elongation at break, and Young's modulus for gelatin films were 13.4 ± 1.2 MPa, 95 ± 5%, and 45.4 ± 7 MPa, respectively. Incorporation of MWCNT caused a significant increase in tensile strength and decrease in the elongation at break. The largest mechanical strength was found at 1.5% MWCNT. All gelatin/MWCNT films showed significant antibacterial activities against both gram-positive and gram-negative bacteria. Our results suggest that the gelatin/MWCNT composites films could be used as a very attractive alternative to traditional materials for different biomedical and food applications.

Encapsulation of cinnamon and thyme essential oils components (cinnamaldehyde and thymol) in β-cyclodextrin: Effect of interactions with water on complex stability

A montmorillonite exchanged with large hydroxy-Al cations was thermally treated to convert the hydroxy cations to oxide pillars and to generate permanent microporosity in the interlayers. The pillared clay products were characterized by X-ray powder diffraction (XRD) and water-sorption measurements to delineate the effect of aging of the pillaring solutions, the methods of drying and concentration of clay-water suspensions, and the temperatures of calcination on micropore volumes. Although samples prepared at different conditions gave d(001) reflections of 17–17.5 Å, at least to 500°C, the concentrations of clay-water suspensions and the temperatures of calcination significantly changed the pore-size distribution and the volume of micropores present in the sample, as calculated from the water-sorption isotherms. A narrow pore-size distribution having little or no macroporosity or external surface condensation was observed in samples prepared by the addition of the pillaring solution directly to the clay (solid) without first making a clay-water suspension and calcining the sample at ≥400°C. About 87% of the total volume was found to be micropores of ≤14–17 Å in the sample calcined at 600°C. Aging the pillaring solution, however, did not influence either the water-sorption isotherms or the XRD patterns significantly under the conditions specified. Essentially the same results were obtained for samples prepared from both hydroxy-Al polymer (OH/Al = 2) and aluminum chlorohydrol (ACH) solutions.Although alumina-pillared clays exhibited an extreme type-I isotherm (Langmuir type) for nitrogen adsorption, the sorption of water vapor gave an isotherm of unusual shape that fit neither a BET nor a Langmuir equation. This latter behavior has previously been attributed to a unique pore size and hydrophobicity and is apparently common to all pillared montmorillonite materials. The hydrophobicity of the pillared clay apparently developed on calcination by the migration of protons from the interlayers to the octahedral sheets, in which sites of cationic substitution (negative charge) were located. Protons migrated back to the interlayers by treatment with NH3, which subsequently converted to NH4+ in the interlayers. The exchange of the NH4+ by Ca2+ introduced hydrophilicity to the alumina-pillared clay, which was reflected both in the shape of the water isotherm (close to moderate Brunauer type I), the heat of sorption, and the total sorption capacity.

Water plays a critical role in protein dynamics and functions. However, the most basic property of hydration--the water sorption isotherm--remains inadequately understood. Surface adsorption is the commonly adopted picture of hydration. Since it does not account for changes in the conformational entropy of proteins, it is difficult to explain why protein dynamics and activity change upon hydration. The solution picture of hydration provides an alternative approach to describe the thermodynamics of hydration. Here, the flexibility of proteins could influence the hydration level through the change of elastic energy upon hydration. Using nuclear magnetic resonance to measure the isotherms of lysozyme in situ between 18 and 2 °C, the present work provides evidence that the part of water uptake associated with the onset of protein function is significantly reduced below 8 °C. Quantitative analysis shows that such reduction is directly related to the reduction of protein flexibility and enhanced cost in elastic energy upon hydration at lower temperature. The elastic property derived from the water isotherm agrees with direct mechanical measurements, providing independent support for the solution model. This result also implies that water adsorption at charged and polar groups occurring at low vapor pressure, which is known for softening the protein, is crucial for the later stage of water uptake, leading to the activation of protein dynamics. The present work sheds light on the mutual influence of protein flexibility and hydration, providing the basis for understanding the role of hydration on protein dynamics.

The effectiveness of measuring distances between monovalent and divalent cation sites on enzymes has been examined by 6Li, 7Li, I4N, 15N, 23Na, 39K, 85Rb, 87Rb, and 133Cs nuclear magnetic resonance (NMR). Measurements were made of the paramagnetic effect of enzyme-bound Mn2+ on the longitudinal spin-lattice relaxation rate ( l/Tl) of the monovalent cations by using MnZ+ at the divalent cation site of pyruvate kinase. Distances from MnZ+ to the monovalent cations in the enzyme-Mn2+-M+ complex are as follows: 6Li+, 8.5 A; 7Li+, 8.4 A; 15NH5+, 7.0 A; 133Cs+, 7.7 A. The mea- sured distances in the enzyme-Mn2+-M+-phosphoenol- pyruvate (PEP) complex are as follows: 6Li+, 5.7 A; 7Li+, 5.7 A; I4NH4+, 4.4 A; 15NH4+, 4.4 A; 133Cs+, 6.0 A. In the complex with PEP, a lower limit distance could be placed on MnZ+ to 23Na+ (24.5 A), 39K+ (23.7 A), and 87Rb+ (24.1 A). These results show a 2-3-A reduction in the distance between MnZ+ and the monovalent cation upon addition of PEP to the enzyme. Additionally, the MnZ+ to monovalent cation dis- A large number of enzymes display an absolute requirement for the addition of a monovalent cation for maximal activity (Suelter, 1970). The most studied enzyme of this group is pyruvate kinase which shows a wide range of maximal ac- tivities depending on the monovalent cation used to activate the enzyme (Kayne, 1973). For example, lithium activates only 2% as well as does potassium. The other monovalent cations are of intermediate activity (Kayne, 1973). It has been observed that the degree of activation of pyruvate kinase by the various monovalent cations appears to correlate with the crystalline ionic radius of these cations. The amount of ac- tivation is found to decrease as the ionic radius increases or decreases relative to that for K+ (Kachmar & Boyer, 1953). However, the precise function of these monovalent cations in catalysis is not known. In an attempt to determine the exact location of the mo- novalent cation site relative to the sites for the other ligands of pyruvate kinase, a number of laboratories have undertaken measurements of the distance from enzyme-bound Mn2+ to the monovalent cation site by using nuclear magnetic resonance (NMR).' Reuben & Kayne (1971) have reported distances of 4.9 and 8.2 A between 205Tl+ and Mn2+ in the enzyme- Mn2+-T1+-phosphoenolpyruvate (PEP) complex and the en- zyme-Mn2+-T1+ complex, respectively. In a 7Li NMR study, Hutton et al. (1977) reported distances of 5.8 and 11 .O A for these enzyme-Mn2+ complexes with 7Li+. Since Li+ activates

Water sorption in hydrophobic porous materials: isotherm shapes and their meanings for the mesoporous MCM-41 and the microporous AIPO4-5

An improved method for the simultaneous determination of water uptake and swelling of tablets