Alcohol-water Mixtures Research Articles

Control of Boiling Instabilities in a Two-Phase Pumpless Loop Using Water-Alcohol Mixtures

AbstractThe mitigation of boiling instabilities by using water-alcohol mixtures as coolants in a two-phase pumpless loop is experimentally investigated. Water-miscible alcohol, namely, 2-propanol, is added to water in quantities of 0.05, 0.1, and 0.2 mol fractions to reduce the bubble departure diameters. Boiling experiments are carried out in the pumpless loop involving a copper-based split-flow microchannel evaporator. Two-phase flow stability and heat transfer performance are compared between pure water and 2-propanol-water mixtures. Temperature measurements at the evaporator inlet, evaporator outlet, and condenser inlet show a considerable reduction in fluctuations when the binary mixtures are used as coolants. Therefore, the addition of a small amount of alcohol to water is proposed as a simple technique to control two-phase flow instabilities as against complex geometry modification to the evaporator, often studied in the literature. The pumpless loop with water-alcohol mixtures is a viable thermal management solution for power electronic devices that involve time-varying workloads.

Bio-waste-derived few-layered graphene/SrTiO3/PAN as efficient photocatalytic system for water splitting

Bio-waste-derived few-layered graphene/SrTiO3/PAN photocatalytic systems obtained via electrospinning technique have been investigated as promising, inexpensive and efficient photoelectrochemical materials for hydrogen production through the solar water-splitting. For the first time, a few-layered graphene synthesized from biologically waste materials such as a rice husk and walnut shell was used as a co-catalyst in a composite photocatalytic system. Results obtained in this work showed that the presence of the graphene is not only promoting the decrease of the band gap of the photocatalytic system, but also positively alter the effective separation of photoinduced charges. At the same time, those composite photocatalytic systems demonstrated a higher rate of the hydrogen release during the water splitting reaction when compared with the pure SrTiO3. Performance of the bio-waste-derived few-layered graphene/SrTiO3/PAN as a photocatalyst in the water-splitting reaction under the UV has been investigated. The developed photocatalytic systems based on few-layered graphene derived from bio-wastes, SrTiO3 and PAN are perspective candidates for production of hydrogen under splitting water-alcohol mixtures.

Operational Limits in Processes with Water, Salt, and Short-Chain Alcohol Mixtures as Aqueous Two-Phase Systems and Problems in Its Simulation

The low critical solution temperature (LCST) and minimum salt concentration that cause phase splitting in water and short-chain alcohol mixtures were determined experimentally. The short-chain alcohols, which are completely miscible with water (methanol, ethanol, 1-propanol, 2-propanol, and tert-butanol) and most of the common salts (those with Na+, K+, Ca2+, and NH4+ cations and Cl–, SO42–, CO32–, and NO3– anions), were studied. Experimentally determined data increased future development opportunities of column sequences and process design using aqueous two-phase systems (ATPSs) by establishing alcohols, some salts, and their operational limits. An example using these systems in phase transition extraction (PTE) separation processes was proposed and discussed. Finally, the use of different thermodynamic models, such as the extended UNIQUAC for electrolytes and the electrolyte nonrandom two-liquid (NRTL) model, for equilibrium calculations and the LCSTs necessary for simulation of these extraction processes with ATPS systems were analyzed.

Correlating solvation with conformational pathways of proteins in alcohol-water mixtures: a THz spectroscopic insight.

Water, being an active participant in most of the biophysical processes, is important to trace how protein solvation changes as its conformation evolves in the presence of solutes or co-solvents. In this study, we investigate how the secondary structures of two diverse proteins - lysozyme and β-lactoglobulin - change in the aqueous mixtures of two alcohols - ethanol and 2,2,2-trifluoroethanol (TFE) using circular dichroism measurements. We observe that these alcohols change the secondary structures of these proteins and the changes are protein-specific. Subsequently, we measure the collective solvation dynamics of these two proteins both in the absence and in the presence of alcohols by measuring the frequency-dependent absorption coefficient (α(ν)) in the THz (0.1-1.2 THz) frequency domain. The alcohol-water mixtures exhibit a non-ideal behaviour with the highest absorption difference (Δα) obtained at Xalcohol = 0.2. The protein solvation in the presence of the alcohols shows an oscillating behaviour in which Δαprotein changes with Xalcohol. Such an oscillatory behaviour of protein solvation results from a delicate interplay between the protein-water, protein-alcohol and water-alcohol associations. We attempt to correlate the various structural conformations of the proteins with the associated solvation.

Core-softened water-alcohol mixtures: the solute-size effects.

Water is the most anomalous material on Earth, with a long list of thermodynamic, dynamic and structural behaviors that deviate from what is expected. Recent studies have indicated that these anomalies may be related to a competition between two liquids, which means that water has a potential liquid-liquid phase transition (LLPT) that ends at a liquid-liquid critical point (LLCP). In a recent study [J. Mol. Liq., 2020, 320, 114420], using molecular dynamics simulations and a core-softened potential approach, we have shown that adding a simple solute such as methanol can "kill" the density-anomalous behavior as the LLCP is suppressed by spontaneous crystallization in a hexagonal close packing (HCP) crystal near the LLPT. Now, we extend this work to realize how longer-chain alcohols will affect the complex behavior of water-alcohol mixtures in the supercooled regime. Besides core-softened (CS) methanol, ethanol and 1-propanol were added to a system of identical particles that interact through the continuous shouldered well (CSW) potential. We observed that the density anomaly gradually decreases its extension in phase diagrams until it disappears with the growth of the non-polar chain and the alcohol concentration, different from the liquid-liquid phase transition (and the LLCP), which remained present in all analyzed mixtures, according to Nature, 2001, 409, 692. For our model, the longer non-polar chains and higher concentrations gradually impact the competition between the scales in the CS potential, leading to a gradual disappearing of the anomalies until the TMD total disappearance is observed when the first coordination shell structure is also affected: short-range ordering is favored, leading to less competition between short- and long-range ordering and, consequently, to the extinction of anomalies. Also, the non-polar chain size and concentration have an effect on the solid phases, favoring the hexagonal close packed (HCP) solid and the amorphous solid phase over the body-centered cubic (BCC) crystal. These findings help to elucidate the behavior of water solutions in the supercooled regime and indicate that the LLCP can be observed in systems without density-anomalous behavior.

Effective Debye relaxation models for binary solutions of polar liquids at terahertz frequencies.

There are many effective medium models that accurately describe the dielectric properties of mixtures. However, these models assume that the components are non-interacting. This assumption is not valid for solutions of polar liquids, resulting in significant deviations between the measured and theoretically predicted values of the complex index of refraction of the mixtures. We present three effective medium theories by expanding the well-known Debye relaxation model for solutions of polar liquids in the terahertz (THz) regime. The new effective medium models proposed in this paper predict the individual relaxation Debye parameters based on the cooperative motion dynamics and self-associative properties of each mixture, and therefore explain the deviation of the dielectric functions of the solutions from the traditional effective medium models. These models are verified through reflection measurements of four alcohol-water solutions acquired through THz time-domain spectroscopy (THz-TDS). Compared to the current mixed medium models, the new effective Debye theorem predicts the dielectric properties of polar solutions more accurately and has the potential to explain inter-species mixing schemes and interactions.

The molecular structure of the surface of water-ethanol mixtures.

Mixtures of water and alcohol exhibit an excess surface concentration of alcohol as a result of the amphiphilic nature of the alcohol molecule, which has important consequences for the physico-chemical properties of water-alcohol mixtures. Here we use a combination of intensity vibrational sum-frequency generation (VSFG) spectroscopy, heterodyne-detected VSFG (HD-VSFG), and core-level photoelectron spectroscopy (PES) to investigate the molecular properties of water-ethanol mixtures at the air-liquid interface. We find that increasing the ethanol concentration up to a molar fraction (MF) of 0.1 leads to a steep increase of the surface density of the ethanol molecules, and an increased ordering of the ethanol molecules at the surface. When the ethanol concentration is further increased, the surface density of ethanol remains more or less constant, while the orientation of the ethanol molecules becomes increasingly disordered. The used techniques of PES and VSFG provide complementary information on the density and orientation of ethanol molecules at the surface of water, thus providing new information on the molecular-scale properties of the surface of water-alcohol mixtures over a wide range of compositions. This information is invaluable in understanding the chemical and physical properties of water-alcohol mixtures.

Eco-Efficient Heat-Integrated Extractive Distillation Process Using Ionic Liquid as Entrainer for Ethyl Acetate-Isopropyl Alcohol-Water Mixture

Eco-Efficient Heat-Integrated Extractive Distillation Process Using Ionic Liquid as Entrainer for Ethyl Acetate-Isopropyl Alcohol-Water Mixture

An environmentally friendly carton adhesive from acidic hydrolysis of waste potato starch

In food industries, especially in factories producing potato chips, large quantities of wastes can be generated that can harm aqueous environments. Before the potato chips are produced, at stages such as cutting and slicing the potato, the potato starches from the blade pass into the aqueous medium. The starch in this aqueous medium can be recycled by centrifuging or decanting before discharging. Otherwise, producing energy by sending it to biogas production facilities is a common method. The industrial starch obtained in this way is referred to as a by-product or waste. Thus, these waste starches, which are renewable, low-cost, multi-functional, biodegradable and nontoxic, can be used in different industries by changing their properties with some physicochemical or chemical methods and can be brought into the economy as cardboard adhesive. The aim of this study was to obtain an environmentally friendly cardboard adhesive from the modification of waste potato starch (WPS) by hydrolysis. WPS was homogenized in different amounts of deionized water and isopropyl alcohol (IPA) mixtures (0–135 mL). Subsequently, the mixtures were hydrolyzed by 25 mL of HCl or H2SO4 at different concentrations (0.25–1.25 M). The structure of the modified potato starch (MWPS) was determined by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD), the surface morphology by scanning electron microscope (SEM), the thermal behavior by thermogravimetric (TGA) analysis, and the viscosity by Brookfield viscosimeter. The adhesive property of the MWPS samples was determined as a tensile strength on a “dog-bone shape” cardboards by texture analyzer. The molecular weight profiles of the starch samples were determined by gel permeation chromatography (GPC) and the effect on the mechanical properties of starch was investigated. The molecular weight of starches was obviously decreased by acid hydrolysis. The observed peaks in the FT-IR spectrum were similar in the WPS and MWPS samples, and not affected by the type and concentration of the IPA or acids. In the SEM images, the granules surface of the MWPSs became shrunken and even fractured with the recessed surfaces. As the acid hydrolysis increases, the diffraction of crystalline peaks, and the thermal stability and degradation temperatures decreased. The viscosity significantly decreased with the increasing of the acid concentration. The best adhesive was obtained from the hydrolysis of 0.50 M HCl (25 mL) in 135 mL of water with the strength of 10.90 MPa.

Improvement of Component Flux Estimating Model for Pervaporation Processes.

Separating non-ideal mixtures by pervaporation (hence PV) is a competitive alternative to most traditional methods, such as distillation, which are based on the vapour–liquid equilibrium (VLE). It must be said, in many cases, accurate VLE data are already well known in the literature. They make the method of PV modelling a lot more complicated, and most of the viable models are (semi)empirical and focus on component flux (Ji) estimation. The pervaporation model of Mizsey and Valentinyi, which is based on Rautenbach’s works, is further improved in this work and tested rigorously by statistical means. Until now, this type of exponential modelling was only used for alcohol–water mixtures, but in this work, it was extended to an ethyl acetate–water binary mixture as well. Furthermore, a flowchart of modelling is presented for the first time in the case of an exponential pervaporation model. The results of laboratory-scale experiments were used as the basis of the study and least squares approximation was used to compare them to the different model’s estimations. According to our results, Valentinyi’s model (Model I) and the alternative model (Model III) appear to be the best methods for PV modelling, and there is no significant difference between the models, mainly in organophilic cases. In the case of the permeation component, Model I, which better follows the exponential function, is recommended. It is important to emphasize that our research confirms that the exponential type model seems to be universally feasible for most organic–water binary mixtures. Another novelty of the work is that after PDMS and PVA-based membranes, the accuracy of the semiempirical model for the description of water flux on a PEBA-based membrane was also proved, in the organophilic case.

Extracts of medicinal plants with natural deep eutectic solvents: enhanced antimicrobial activity and low genotoxicity

Natural deep eutectic solvents (NADES) are a new alternative to toxic organic solvents. Their constituents are primary metabolites, non-toxic, biocompatible and sustainable. In this study four selected NADES were applied for the extraction of two medicinal plants: Sideritis scardica, and Plantago major as an alternative to water-alcohol mixtures, and the antimicrobial and genotoxic potential of the extracts were studied. The extraction efficiency was evaluated by measuring the extracted total phenolics, and total flavonoids. Best extraction results for total phenolics for the studied plants were obtained with choline chloride-glucose 5:2 plus 30% water; but surprisingly these extracts were inactive against all tested microorganisms. Extracts with citric acid-1,2-propanediol 1:4 and choline chloride-glycerol 1:2 showed good activity against S. pyogenes, E. coli, S. aureus, and C. albicans. Low genotoxicity and cytotoxicity were observed for all four NADES and the extracts with antimicrobial activity. Our results confirm the potential of NADESs for extraction of bioactive constituents of medicinal plants and further suggest that NADES can improve the effects of bioactive extracts. Further studies are needed to clarify the influence of the studied NADES on the bioactivity of dissolved substances, and the possibility to use such extracts in the pharmaceutical and food industry.

THE STUDY OF THE EXTRACTION DYNAMICS OF BIOLOGICALLY ACTIVE SUBSTANCES FROM THE BIDENS TRIPARTITA L. HERB AND ANTIOXIDANT ACTIVITY OF THE OBTAINED EXTRACTS

The interest to study the genus Bidens and in particular Bidens tripartita L. (bur-marigold herb) is unmitigated due to its antioxidant, anti-allergic, antimicrobial, antifungal, hepatoprotective, immunostimulating and hypotensive activity. This pharmacological activities are determined by the presence of flavonoids, polyphenolic compounds, polysaccharides, components of essential oils, polyacetylenes, etc. The aim of the research was to study the process of extracting various biologically active substances (polysaccharides, flavonoids, polyphenols) from bur-marigold herb with water-alcohol mixtures of various concentrations, to study their component composition, as well as to evaluate their effect on the oxidative effect of free radicals. Materials and methods. The object of the research was the herb of Bidens tripartita L. Raw materials were collected and procured on the territory of Kharkiv, Zhytomyr and Poltava regions of Ukraine. All used methods for the quantitative determination of biologically active substances were pharmacopeial and described in various monographs in the European Pharmacopoeia and State Pharmacopoeia of Ukraine. Results. The extracts of the bur-marigold herb were analyzed for the content of the extractable matter, flavonoids, polysaccharides and it was found that they are maximally extracted (about 80 %) in the 1st percolate with a drug/solvent ratio of 1:10 for all the extractants. It was found that with an increase of ethanol concentration in the extraction mixture, the content of polyphenols and flavonoids, is expectedly increased, as well as the value of the antioxidant activity of the corresponding extracts, but the amount of extracted polysaccharides is significantly reduced. Conclusions. With the selected evaluation criteria, it was found that 40 % ethanol is optimal from the point of view of balanced extraction of flavonoids, polysaccharides and polyphenols. A strong positive and statistically significant correlation was found between the content of polyphenols in the obtained extracts and their antioxidant activity (Pearson correlation coefficient, r=0.9998), slightly weaker for flavonoids (r=0.9886), and an inverse correlation between polysaccharides content and TEAC- value.

Separation of Alcohol-Water Mixtures by a Combination of Distillation, Hydrophilic and Organophilic Pervaporation Processes.

It can be stated that in the fine chemical industries, especially in the pharmaceutical industry, large amounts of liquid waste and industrial waste solvents are generated during the production technology. Addressing these is a key issue because their disposal often accounts for the largest proportion of the cost of the entire technology. There is need to develop regeneration processes that are financially beneficial to the plant and, if possible, reuse the liquid waste in the spirit of a circular economy, in a particular technology, or possibly elsewhere. The distillation technique proves to be a good solution in many cases, but in the case of mixtures with high water content and few volatile components, this process is often not cost-effective due to its high steam consumption, and in the case of azeotropic mixtures there are separation constraints. In the present work, the membrane process considered as an alternative; pervaporation is demonstrated through the treatment of low alcohol (methanol and ethanol) aqueous mixtures. Alcohol-containing process wastewaters were investigated in professional process simulator environment with user-added pervaporation modules. Eight different methods were built up in ChemCAD flowsheet simulator: organophilic pervaporation (OPV), hydrophilic pervaporation (HPV), hydrophilic pervaporation with recirculation (R-HPV), dynamic organophilic pervaporation (Dyn-OPV), dynamic hydronophilic pervaporation (Dyn-HPV), hybrid distillation-organophilic pervaporation (D + OPV), hybrid distillation-hydrophilic pervaporation (D + HPV), and finally hybrid distillation-hydrophilic pervaporation with recirculation (R-D + HPV). It can be stated the last solution in line was the most suitable in the terms of composition, however distillation of mixture with high water content has significant heat consumption. Furthermore, the pervaporation supplemented with dynamic tanks is not favourable due to the high recirculation rate in the case of tested mixtures and compositions.

Дослідження технологічних параметрів сировини трави Ельшольції Стаунтона та трави Ельшольції війчастої для одержання екстрактів

Мета дослідження – визначення технологічних параметрів подрібненої рослинної сировини трави Ельшольції Стаунтона та трави Ельшольції війчастої (Патрена).Наведено результати дослідження технологічних параметрів подрібненої рослинної сировини: трави Ельшольціі Стаунтона (Elsholtzia Stauntonii Benth.) і трави Ельшольції війчастої (Патрена) (Elsholtzia ciliata, Elsholtzia Patrena Thunb.), що необхідні для розробки оптимальної технології отримання екстрактів у лабораторних і промислових умовах: вологiсть, питома, об’ємна та насипна густина сировини, пористiсть, порiзнiсть, вiльний об’єм шару, втрата в масі за висушування, зола загальна та зола нерозчинна в хлористоводневій кислоті, коефіцієнт поглинання. Також було визначено закономірність виходу екстрактивних речовин з обох видів сировини залежно від використаного екстрагента (вода, водно-спиртові суміші).Використовувались інструментальні та гравіметричні методи.У результаті проведених аналізів визначено наступні основні технологічні параметри трави Ельшольціі Стаунтона: питома густина – (1,26 ± 0,08) г/см3, об’ємна густина – (0,46 ± 0,03) г/см3, насипна густина – (0,078 ± 0,005) г/см3, пористість – (0,60 ± 0,04), порізність – (0,76 ± 0,04), вільний об’ємшару – (0,90 ± 0,05), зола загальна – (10,21 ± 0,61)%, зола нерозчинна в хлористоводневій кислоті – (0,58 ± 0,03) %, втрата в масі за висушування – (7,82 ± 0,23) %. Технологічні параметри трави Ельшольції війчастої: питома густина – (0,82 ± 0,05) г/см3, об’ємна густина – (0,30 ± 0,02) г/см3, насипна густина – (0,051 ± 0,003) г/см3, пористість – (0,39 ± 0,02), порізність – (0,52 ± 0,03), вільний об’єм шару – (0,75 ± 0,04), зола загальна – (8,75 ± 0,52) %, зола нерозчинна в хлористоводневій кислоті – (1,20 ± 0,07) %, втрата в масі за висушування – (6,59 ± 0,19) %.Домінуючий вихід екстрактивних речовин з трави Ельшольції Стаунтона спостерігався в разі використання 20 % етанолу як екстрагента, а з трави Ельшольції війчастої – води. Найкраща екстракція речовин з обох видів сировини досягається за співвідношення сировина:екстрагент 1:50.

On-Off of Co-non-solvency for Poly(N-vinylcaprolactam) in Alcohol-Water Mixtures: A Molecular Dynamics Study.

Poly(N-vinylcaprolactam) (PVCL) exhibits co-non-solvency in aqueous solutions of 2-propanol but not in methanol. What distinguishes the impact of these two cosolvents on the polymer conformational stability? We report a molecular dynamics simulation study on PVCL 50-mer and monomers dissolved in methanol-water and 2-propanol-water mixtures. We show that the alcohol-concentration dependence of the effective attraction between a pair of PVCL monomers closely resembles the conformational changes in a single PVCL 50-mer as well as the experimentally observed behavior for PVCL chains. We also found that, at the co-non-solvency maximum, the monomer-monomer attraction works over a long-range beyond the solvent-separated distance. Then, we correlate the long-range attraction to the appearance of a dense alcohol concentration accumulated between the monomers. Furthermore, we distinctly demonstrate that the co-non-solvency of PVCL monomers can be switched on/off by artificially tuning the alcohol size while keeping the energetic parameters. Thus, we conclude that the magnitude of the excluded volume effect in alcohol accompanying the gain in translational entropy of the solvent is crucial to the occurrence of PVCL polymer co-non-solvency.

Chitosan Oligosaccharide Based Hydrogel: an Insight into the Mechanical, Drug Delivery, and Antimicrobial Studies

Hydrogel is a macromolecular polymer gel constructed of a network of cross-linked polymer chains. Chitosan oligosaccharide (CO) is a natural polymer that has an efficient biodegradability and is used to prepare hydrogels for efficient drug delivery. CO is combined with Carboxy Methyl Cellulose (CMC) to produce a hydrogel in different compositions for the best suitable option where the drug delivery and biocompatibility are most efficient. The chemical hydrogels of the composition CO and CMC were prepared by adding the cross-linker mixture of glutaraldehyde, alcohol, and distilled water. After the hydrogels were prepared, it is subjected to a series of tests, i.e., microscopy, hemocompatibility, mechanical strength, impedance measurement, drug release, antimicrobial activity. Ccross-linking is achieved by adding a mixture of glutaraldehyde, alcohol, and distilled water. Thus, the best composition of the mixture of the two compounds – Chitosan oligosaccharide and the Carboxy Methyl Cellulose is determined and used for efficient drug delivery.

Recycling of discarded coin cells for recovery of metal values

Lithium-metal primary batteries, widely used in portable electronics, contain lithium, manganese, and carbon, which can be recycled to conserve resources and prevent environmental damage. This study investigates the thermal response of active material under ambient conditions and its effects on manganese dissolution in organic acid. Thus, spent lithium metal batteries were manually dismantled, the lithium they contain was dissolved in a mixture of distilled water and isobutyl alcohol, and the steel and active cathode material were mechanically separated. The thermal exposure of active material comprising MnO2 and C resulted in carbothermal reduction with products Mn3O4 and MnO. The composition of product at optimum condition (800 °C, 30 min) comprises 60 wt% Mn, 21.5 wt% O, and 18.5 wt% C in the form of MnO, Mn3O4, and C. Manganese extraction increased significantly on thermal treatment, yielding 81% at optimum condition. Therefore, thermal treatment for the indigenous reduction of MnO2, followed by leaching in an organic acid, is proposed for lithium and manganese value recovery from spent coin cells. The activation energy for thermal dissociation of active material has been identified as 20.96 kJ/ mol, and mass balance for the process followed has also been investigated.

Nanostructure of a Catalyst Ink Investigated by Contrast-Variation Small-Angle Neutron Scattering

One of the major aims when investigating catalyst inks for polymer electrolyte fuel cell applications is to understand the relationship between their macroscale physical properties and nanostructure. Catalyst inks are complex colloidal dispersions consisting of catalyst particles, ionomers, and water–alcohol mixtures. Some of the ionomer is adsorbed onto the surface of the catalyst particles. Due to the electrostatic repulsion observed between the particles covered with the ionomer, the ink possesses high dispersion stability. Meanwhile, the role of the remaining ionomer in the dispersion is unclear to date. To clarify the effect of the non-adsorbed ionomer on the physical properties of a catalyst ink, we have established a method to elucidate the amount of non-adsorbed ionomer in the catalyst ink using contrast-variation small-angle neutron scattering (CV-SANS). CV-SANS measurements revealed that the volume fraction of the non-adsorbed ionomer in catalyst ink monotonically increases upon increasing the weight ratio of ionomer/carbon. It was found that the non-adsorbed ionomer in the catalyst ink acts as a typical ionomer dispersion, which can be described by the Huggins equation at high shear viscosity. Our findings may serve as useful guidelines for the preparation of catalyst inks, which is a crucial step for the construction of rationally designed membrane electrode assemblies used for polymer electrolyte fuel cell applications.

Nanostructure of a Catalyst Ink Investigated by Contrast-Variation Small-Angle Neutron Scattering

One of the major aims when investigating catalyst inks for polymer electrolyte fuel cell applications is to understand the relationship between their macroscale physical properties and nanostructure. Catalyst inks are complex colloidal dispersions consisting of catalyst particles, ionomers, and water–alcohol mixtures. Due to the electrostatic repulsion observed between the particles covered with the ionomer, the ink possesses high dispersion stability. Meanwhile, the role of the remaining ionomer in the dispersion is unclear to date. We have established a method to elucidate the amount of non-adsorbed ionomer in the catalyst ink using contrast-variation small-angle neutron scattering (CV-SANS). CV-SANS measurements revealed that the volume fraction of the non-adsorbed ionomer in the catalyst ink monotonically increases upon increasing the weight ratio of ionomer/carbon. It was found that the non-adsorbed ionomer in the catalyst ink acts as a typical ionomer dispersion, which can be described by the Huggins equation at high shear viscosity.

Viscosity study of tert-butyl alcohol aqueous solution by Brownian motion and gravimetric capillaries

Molecular interactions influence the viscosity of liquids and reveal the nature of liquid mixtures. Water and tert-butyl alcohol mixtures exhibit strange viscosity behavior induced by concentration differences. The macroscopic viscosity of the aqueous alcohol solutions was examined with a Ubbelohde viscometer and a gravimetric capillary. The microscopic viscosity was calculated from the trajectory analysis of the Brownian motion of 1 μm sized polystyrene beads. A discrepancy between the macroscopic and microscopic viscosity was observed specifically at lower concentrations, indicating that the water fluctuation in the solution is critical for the Brownian motion. A new method investigating molecular interactions using Brownian motions is demonstrated.