Water Uptake Values Research Articles

Cellulose-based film modified by succinic anhydride for the controlled release of domperidone

Succinic anhydride (SAD) modified microcrystalline cellulose (MCC) films was prepared and used for the controlled release of the drug domperidone (dom). The morphology and chemical structure of the modified materials were characterized by SEM, FTIR, XRD and TG/DSC techniques. The physical properties, such as water uptake and swelling, light barrier properties, mechanical testing, in vitro degradation behavior, have been investigated. Results showed that the modified cellulose membranes exhibited good anti-UV properties, higher water uptake values, improved mechanical capacity and anti-biodegradability. In addition, the modified MCC films (MS) as the drug carrier indicated the controlled release of domperidone and the release mechanism was proposed using Korsmeyer–Peppas equation at pH 7.4. The developed drug delivery system possessed the profound significance in improving pharmacodynamics and bioavailability of drugs.

Sulfonated Fe3O4@SiO2 nanorods incorporated sPVdF nanocomposite membranes for DMFC applications

The magnetite needle like nanorods and its core-shell architecture with silica were incorporated into the sulfonated poly(vinylidene fluoride) (sPVdF) membrane and the influence of nanofillers towards direct methanol fuel cell (DMFC) performances was investigated in detail. The morphological properties enunciated that magnetite@silica needle like nanorods were uniformly distributed over the sPVdF matrix. The sulfonated magnetite@silica positively influenced the water uptake and ion exchange capacity values via its water adsorption and acidification characteristics, respectively. The hydrogen bonding exerted between the surface functional groups of sulfonated magnetite@silica and free water molecules promoted the ion conduction properties of sPVdF membrane. The tortuous pathways and narrower transportation channels of sPVdF/sulfonated magnetite@silica membrane limited the methanol permeation. By the synergetic combination of acidification of polymer and nanocomposite techniques, the existing constrains of PVdF membrane were effectively tackled and the sPVdF/sulfonated magnetite@silica (3 wt%) membrane exhibited the peak power density of 120 mW cm−2 associated with the durability of 150 h at 60 °C, demonstrating the potential applicability of magnetite@silica fillers in DMFCs.

PVDF/magnetite blend membranes for enhanced flux and salt rejection in membrane distillation

This study reports on the enhancement of direct contact membrane distillation (DCMD) performance by incorporating magnetite nanoparticles (NP) in polyvinylidene fluoride (PVDF) membranes to render the membrane bulk hydrophilic while maintaining a hydrophobic top surface. Hansen solubility parameters (HSP) were first calculated to assess the affinity/compatibility of NP with the polymer, dope solution and aqueous feed. Extensive characterizations were done to elucidate the structural and physiochemical properties of the blend membranes. Energy dispersive spectrometry (EDS) analyses confirmed the uniform distribution of NP within the membrane matrix. Contact angle values showed that the NP did not compromise the hydrophobicity of the membrane top layer. The blend membrane had a 92% higher water uptake value, compared to the pristine sample, indicating the high hydrophilicity of the membrane bulk. Blend membrane also showed higher (ca. 36%) DCMD flux, due to their hydrophilic sub-layer, without compromising the salt rejection. Leaching tests were conducted using both water and concentrated acid to confirm the presence of nanoparticles and to demonstrate the membrane stability in aqueous medium.

The Effect of Carboxyl Group Content on Water Uptake Capacity and Tensile Properties of Functionalized Soy Protein-Based Superabsorbent Plastics

This manuscript studies the relation between macroscopic properties of the soy protein isolate (SPI)-based superabsorbent polymers (SAP) (e.g., water uptake capacity and tensile properties) and the extent of chemical modification conducted on the protein. The increase in the carboxyl group content, obtained from electrometric titrations, for acylated systems compared to native SPI brings with it an improvement in the protein hydrophilic character, as revealed by the determination of the water imbibing capacity. SEM images show that larger porous regions were developed in the acylated plastics. As for their mechanical properties, static tensile measurements indicated that acylated plastics with greater water uptake values display higher extensibility, compared to the reference sample. These natural-based SAP materials could be appropriate for applications in which maintaining the dimensional stability during service is not crucial (e.g. in agriculture and horticulture).

Advanced processing and characterization of Nafion electrolyte films for solid-state electrochromic devices fabricated at room temperature on single substrate

The design and development of effective solid-state electrolytes represent an emerging challenge towards the fabrication of electrochromic (EC) and multifunctional devices, such as photoelectrochromics, with benefits in terms of reduced cost, environmental impact as well as safety. Here, we present the processing and the characterization of a suitable Nafion film with the certain thickness of 8μm used as electrolyte layer in a novel solid-state EC device fabricated at room temperature (RT) on a single substrate (both glass and plastics) with an architecture based on a substrate/ITO/WO3/Nafion-film/ITO configuration. In particular, we focused on the morphological characteristics, proton conductivity and water molecular dynamics of Nafion film in order to provide insight into the EC behavior of these novel devices. EIS analysis performed over a wide range of RH and temperature, showed good proton conductivity values (e.g. 4.42×10−3Scm−1 at 30°C and 50% RH), suitable for practical EC operation. At the same time, high values of water self-diffusion coefficients (D) and the spin-lattice relaxation times (T1) were measured by NMR spectroscopy, proving a similar behavior as well as the same proton conduction mechanism with that observed for thicker Nafion membrane (50μm thick) prepared by solution casting. These findings were confirmed by the water uptake measurements since both the film and the membrane showed a water uptake value of about 24wt%. Furthermore, a homogenous, uniform and very smooth surface (Ra of 0.94nm) with small grain size (ca. 50nm) was observed by SEM and AFM analysis. Noteworthy, the Nafion film ensured high optical properties, interfacial robustness and electrochemical stability to EC device: cyclability (300 CV cycles), long-term durability of at least 1000 chronoamperometric cycles.

Non-destructive testing of concrete treated with penetrating surface sealant using a Karsten-tube

Surface treatment is increasingly becoming acceptable as a means of ensuring concrete durability by way of controlling or preventing the ingress of various deleterious agents of concrete deterioration. In practice, a combination of non-destructive and semi-destructive evaluation of the concrete surface is often necessary to decide on the need for treatment or re-treatment of previously treated surfaces. The owners of structures and restorers appreciate simple and non-destructive methods in making any interventions on surfaces that have been treated previously. Existing knowledge would suggest that correct interpretation of these test results would depend on an understanding of the effect of factors such as the initial moisture content, quality of the concrete and exposure conditions. This paper presents the result of a study to assess the applicability of the “Karsten-tube” in measuring the water uptake of treated and un-treated concrete surfaces and the effects of the concrete quality, and environmental conditions upon the test results. The results are compared with complementary tests for oxygen permeability and porosity of the concrete specimens studied. Three concrete mixes and five different exposure conditions were investigated. Some specimens were soaked in 3% Sodium Chloride solution to study the effects of aggressive agents. The results indicates that Karsten-tube is a quick non-destructive method for obtaining useful information about the condition of treated and un-treated concrete surfaces and could be used for rapid and reliable assessment of the need for re-treatment of previously treated surfaces. Well-treated surfaces will have low water uptake values, irrespective of the quality of the concrete.

Effect of pigment and temperature onto swelling and water uptake during organic coating ageing

Free films and coatings of a model epoxy system, with or without pigment (TiO2), were aged in saline solution at different temperatures (30°C, 40°C and 50°C). The water uptake was evaluated using gravimetry for free film and using electrochemical impedance spectroscopy (EIS) for coatings. In parallel, the swelling of coatings was in situ monitored using scanning electrochemical microscopy (SECM).It was shown that the temperature has no effect on the water uptake values for unpigmented systems and a slight effect onto swelling. For pigmented systems, the water uptake values slightly increase likely due to additional water absorption at the pigment/binder interphase. The swelling of pigmented coating was found to be lower than that of unpigmented coatings for all ageing temperatures. This result was explained by particular internal stresses that develop in pigmented system.Water uptake values obtained from gravimetry and EIS, using the Brasher and Kingsbury equation, were different for all the temperatures for unpigmented and pigmented coatings. Using a modified Brasher and Kingsbury equation that considers the experimental swelling obtained by SECM, the same water uptake values were obtained for all systems and all temperatures. Finally, it appears that the coating swelling is a key parameter to evaluate water uptake in organic coatings, especially when different coatings are compared.

Mixed-charge poly(2,6-dimethyl-phenylene oxide)anion exchange membrane for diffusion dialysis in acid recovery

In order to achieve high H+ dialysis coefficients and highly selective of anion exchange membranes (AEMs) for diffusion dialysis (DD) in acid recovery applications, a series of mixed-charge PPO AEMs with quaternary ammonium(QA) and carboxylic acid groups were synthesized quantitatively via Cu(I)-catalysed “click chemistry”. In diffusion dialysis, using an acidic solution (HCl, 1mol/L; FeCl2, 0.2mol/L) as a simulated waste solution indicated that the as-obtained mixed-charge PPO AEMs displayed higher H+ dialysis coefficients and a higher H+/Fe2+ selectivity over that of typical AEMs despite their increased water uptake and lower volumetric IECv values. The highest H+ dialysis coefficients, 0.021m/h, and H+/Fe2+ selectivity 34.52, membranes were achieved with PPO-X35Y20 at 30°C. These values were much higher than that of the PPO-X40 membrane without carboxylic acid groups. Importantly, unlike previously reported AEMs for DD in which the H+/Fe2+ selectivity decreased as the IECw increased, (i.e., a trade-off effect between the UH+ and selectivity), the high IECw of the mixed-charge PPO AEMs tended to result in not only high H+ dialysis coefficients but also high H+/Fe2+ selectivities. It is assumed that the carboxylic acid groups in AEMs likely enhance the dialysis of H+ by the ion changing and hydrogen-bonding more with H+ than Fe2+, thus, cancelling out the ‘trade-off’ effect in DD for acid recovery.

Preparation and Characterization of High Methanol Resistance Sulfonated Poly(ether ether ketone) Membrane for DMFC Application

High methanol resistance sulfonated poly(ether ether ketone) (SPEEK) membranes have been prepared and characterized as a potential proton exchange membrane for direct methanol fuel cell. The sulfonation process was conducted at room temperature to produce SPEEK with 60% degree of sulfonation (DS). The produced membranes were then characterized by evaluating the swelling behavior in terms of water uptake, swelling ratios and methanol sorption as a function of temperature and reaction time. Interestingly, it was observed that the methanol uptake value of SPEEK membrane was lower as compared to the water uptake value as much as 80%. This characteristic showed that SPEEK membrane possesses good resistance towards methanol which is a crucial property requires for direct methanol fuel cell (DMFC) application.

(Invited) Molecular Engineering of Aromatic Polymer Electrolytes for Anion Exchange Membranes

Recently, anion exchange membrane (AEM) fuel cell has attracted attention as a clean energy technology device to convert chemical energy into electric energy. AEM fuel cells have several advantages, such as fast kinetics and non-precious metal catalysts.1 However, desired AEMs should have high hydroxide conductivity, thermochemical stability at high pH for durable operation, and convenient synthetic process.2-5 These challenges can be approached by designing of new polymer backbones, side chain functional groups and new anion conductive groups.6 In designing polymer structure, aryl ether groups are known to cause polymer backbone degradation in high pH environment.5 Several research groups including us have reported that a long side chain between polymer backbone and quaternary ammonium (QA) end group is helpful for enhancing micro-phase separation based on thermochemical stable backbone.7-9 In this study, we will present the effects of polymer structures (i.e. QA group, tether chain, polymer backbone) on AEM characteristics and fuel cell performance, including morphology results. Representative polymer structures of AEM are shown in Figure 1. The physical properties of the precursor polymers and AEM characteristics are summarized in Table 1. We observed morphological difference between m-TPN1 and p-TPN1 membranes from small-angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS). The substitution pattern of the meta-structure membrane (m-TPN1) played a major role in microdomain structures, which contributed to improved conductivity and fuel cell performance. Table 1. Properties of precursor polymers and IECs, water uptake, hydration number, and hydroxide conductivity of ionic polymers Polymer Mn § Mw § PDI IEC a IEC b WU (%) c λ (OH-) d σ (mS cm-1) e 30 °C 80 °C p-TPN1 30.9 61.3 1.98 2.12 2.15 65 17 43 81 m-TPN1 62.2 126.2 2.02 2.15 2.13 70 18 54 112 BPN1-65 f 72.1 138.8 1.93 1.94 1.93 g 85 24 41 88 BPN1-100 f 70.8 110.1 1.6 2.70 2.80 g 124 26 62 122 § kg/mol of precursor polymer. a IEC values by 1H NMR analysis (meq./g). b IECs by 1H NMR analysis after alkaline test at 1M NaOH at 95 °C for 30 days (meq./g). c Water uptake was measured in OH- form at 80 °C. d Based on water uptake value at 80 °C. e hydroxide conductivity. f Reference 8 g Alkaline test at 80 °C (reference 8). 1. Y. J. Wang, J. Qiao, R. Baker, J. Zhang, J., Chem. Soc. Rev. 42 , 5768, (2013). 2. O. M. M. Page, S. D. Poynton, S. Murphy, A. Lien Ong, D. M. Hillman, C. A. Hancock, M. G. Hale, D. C. Apperley, J. R. Varcoe, RSC Adv. 3 , 579 (2013). 3. K. J. Noonan, K. M. Hugar, H. A. Kostalik, E. B. Lobkovsky, H. D. Abruna, G. W. Coates, J. Amer. Chem. Soc.134 , 18161 (2012). 4. J. Ran, L. Wu, T. Xu, Polym. Chem. 4 , 4612 (2013). 5. C. Fujimoto, D.-S. Kim, M. Hibbs, D. Wrobleski, Y. S. Kim, J. Membr. Sci. 423 −424 , 438 (2012). 6. A. D. Mohanty, C. Y. Ryu, Y. S. Kim, C. Bae, Macromolecules 48 , 7085 (2015). 7. H.-S. Dang, P. Jannasch, Macromolecules 48 , 5742 (2015). 8. W.-H. Lee, Y. S. Kim, C. Bae, ACS Macro Lett. 4, 814 (2015). 9. W.-H. Lee, A.D. Mohanty, C. Bae, ACS Macro Lett. 4, 453 (2015). Figure 1

Surface properties of thermally treated composite wood panels

Composite finger-jointed spruce and oak wood panels have been thermally treated under standard pressure and oxygen content conditions at two different temperatures, 180°C and respectively 200°C for short time periods (3 and 5h). Due to the thermally-aided chemical restructuration of the wood components, a decrease in water uptake and volumetric swelling values with up to 45% for spruce and 35% for oak have been registered, comparing to the reference samples. In relation to water resistance, a 15% increase of the dispersive component of the surface energy has been registered for the thermal-treated spruce panels, which impedes water spreading on the surface. The thermal-treated wood presents superior resistance to accelerated UV exposure and subsequently, with up to 10% higher Brinell hardness values than reference wood. The proposed thermal treatment improves the durability of the finger-jointed wood through a more economically and environmental friendly method than traditional impregnation, with minimal degradative impact on the structural components of wood.

Synthesis of novel guanidinium-based anion-exchange membranes with controlled microblock structures

Four guanidinuium-functionalized model compounds containing different substituent groups were prepared, and the substituent effects on the overall alkaline stability of the guanidinium cations were investigated. Based on the good alkaline stability of the model compounds, novel guanidinium-based anion exchange membranes (AEMs), GPP-co-PAEK x, with controlled microblock structures were subsequently designed and synthesized in good yield via a three step reaction that included a fluorophenyl-amine reaction, methylation and nickel (0)-catalyzed coupling. Notably, the use of a hydrophilic, guanidinium cation-containing component as a raw material in the direct synthesis of AEMs via nickel(0)-catalyzed coupling avoided using hygroscopic Vilsmeier salts and is obviously different from the conventional method that involves bromomethylation or post-quaternization. The GPP-co-PAEK x membranes exhibited lower water uptake values (≤23.4% at 60°C) and hydroxide conductivities comparable to those of others reported randomly functionalized guanidinium-based AEMs with similar ion exchange capacity (IEC) values. This finding indicates that the GPP-co-PAEK x membranes with controlled microblock structures possess well-developed hydrophilic/hydrophobic nanophase separation, which was confirmed by transmission electron microscopy (TEM). Moreover, long-term alkaline stability tests demonstrated that the alkaline stability of both the hydrophilic guanidiniums groups and the copolymer backbone contributed to the good alkaline stabilities of the GPP-co-PAEK x membranes.

Enhancement of direct methanol fuel cell performance through the inclusion of zirconium phosphate

Nafion/zirconium hydrogen phosphate (ZrP) composite membranes containing 2.5 wt.% ZrP (NZ-2.5) or 5 wt.% ZrP (NZ-5) were prepared to improve the performance of a direct methanol fuel cell (DMFC). The influence of ZrP content on the Nafion matrix is assessed through characterization techniques, such as Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), and water uptake measurement. Performance testings of the DMFCs based on these composite membranes as well as commercial Nafion® 115 membrane were performed using a computer aided fuel cell test station for different values of cell temperature (40 °C, 60 °C, 80 °C, and 100 °C) and methanol concentration (0.75 M, 1.00 M, and 1.50 M). Characterization studies indicated that incorporation of ZrP into polymer matrix enhanced the water uptake and proton conductivity values of Nafion membrane. The results of the performance tests showed that the Membrane Electrode Assembly (MEA) having NZ-2.5 provided the highest performance with the peak power density of 551.52 W/m2 at 100 °C and 1.00 M. Then, the performances of the MEAs having the same NZ-2.5 membrane but different cathode catalysts were investigated by fabricating two different MEAs using cathode catalysts made of Pt/C–ZrP and Pt/C (HiSPEC® 9100). According to the results of these experiments, the MEA having NZ-2.5 membrane and Pt/C (HiSPEC® 9100) cathode catalyst containing 10 wt.% of ZrP exhibited the highest performance with the peak power density of 620.88 W/m2 at 100 °C and 1.00 M. In addition, short-term stability tests were conducted for all the MEAs. The results of the stability tests revealed that introduction of ZrP to commercial (HiSPEC® 9100) cathode catalyst improves its stability characteristics.

Water uptake in free films and coatings using the Brasher and Kingsbury equation: a possible explanation of the different values obtained by electrochemical Impedance spectroscopy and gravimetry

For many years, the water uptake in organic coatings was measured by EIS and/or gravimetry but differences in water content values were found in almost all studies. The Brasher-Kingsbury equation used in the electrochemical analysis (EIS) is often criticized because elementary assumptions may be unvalid. The origin of the discrepancy between both methods is still of interest because many questions remain open and this study aims to provide new insights to these questions.In this work, free films and coatings of a model epoxy-amine system were immersed in a 3wt.% NaCl solution. The water uptake in free films was evaluated using gravimetric measurements and EIS, using the Basher-Kingsbury equation. The mass of free-films used in the EIS tests was measured and compare to gravimetric measurements while the water uptake (EIS) in free films was compared to that obtained with coatings. It was found that the mass increase of free films tested with EIS was in agreement with gravimetric measurements but was always lower than the water uptake obtained by EIS. Moreover, the water uptake in free films (EIS) was different from that obtained with coatings. In all cases, it was found that the Basher-Kingsbury equation overestimated the water uptake.It appears that the differences between EIS and gravimetric measurements can be analyzed in terms of geometrical effects. Indeed, the swelling in free films and coatings can be monitored by DMA and SECM during ageing. Finally, by mixing the experimental swelling data and the Brasher-Kingsbury equation, the same value of water uptake was obtained by EIS and gravimetry for coatings.

Hydroxide Ion Highway Constructed by Orderly Aligned Quaternary Ammonium Groups in Anion Exchange Membranes

Self-assembly of Gemini surfactants (maleic alkylene group diethylbis [octyl dimethyl bromide], abbreviated as G16-2-16) were used to form reversed micelles by introducing sodium salicylate (NaSal) into chloroform solution of PSF (polysulfone). The rheological measurements indicated that micelles had been formed. The internal surface of micelles were full of orderly arranged quaternary ammonium (QA) groups as cationic active sites. Then we characterized the composite membranes which were introduced micelles, it turned out that, the OH− conductivity in presence of NaSal was higher than the absence one, indicating that the formation of reversed micelles arranged the cationic active sites more orderly, resulted in improving the anionic conductivity by 40–80%, especially under low values of water uptake and ion exchange capacity condition, which provided a kind of approach of enhancing OH− migration efficiency without sacrificing its dimensional stability and mechanical properties. The composite membranes also showed an outstanding thermal stability. And 240 h high temperature alkaline-stable test (10 M NaOH) revealed that the largest decline of OH− conductivity was only round about 4%, which showed excellent alkaline resistance stability.

Assessing and Modifying Macroscopic Root Water Extraction Basil (Ocimum basilicum) Models under Simultaneous Water and Salinity Stresses

Core Ideas: Determining basil's salinity coefficients, including the threshold value to salinity (h0*) and the yield reduction gradient (b). Estimating the h*, h50, p1, and α01 parameters based on measured daily relative transpiration (with water stress treatments). Estimating the h0*, h050, b, p2, and α02 parameters, under 13 proposed salinity levels (1.175, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.5, 4, 5, 6, 8, and 10 dS m–1) in addition to the main experiment to calibrate the salinity parameters. Evaluating basil root water uptake models under simultaneous water and salinity stress conditions. Introducing a modified conceptual basil model based on the collected data and programming of an M‐file in MATLAB and verifying this modified conceptual basil model for h3 (the soil water pressure head threshold in linear macroscopic root water extraction models under water stress conditions) based on experimental data In arid and semiarid regions, plants are often subjected to both water scarcity and soil salinity. Our objectives were to compare several equations describing the combined effects of water and salinity stress on root water uptake and to improve one of the equations. Consequently, seven macroscopic root water extraction models were evaluated using basil (Ocimum basilicum L.) experimental data. An experiment was conducted with four irrigation water salinities [1.175 (S1), 3 (S2), 5 (S3), and 8 (S4) dS m–1] and four irrigation levels: 120 (W1), 100 (W2), 80 (W3), and 60% (W4) of crop water requirements, each with three replicates. Among the root water uptake models, the modified Homaee et al. model provided the best agreement with the experimental data. Because of the high sensitivity of basil to both water and salinity stresses, the root water uptake threshold value was low. Increased salinity decreased the potential at which the root water uptake ceased. These values for S1, S2, S3, and S4 were 3184, 2750, 2215, and 1650 cm, respectively. The h3 parameter (the threshold soil water pressure head in linear root water extraction models) was also influenced nonlinearly by salinity: h3 under the S1, S2, S3, and S4 salinity treatments were 510, 481, 354, and 295 cm, respectively. These findings can be used for scheduling irrigation accurately, determining actual crop water requirements and thus managing the quantity and quality of irrigation water more efficiently, and solving the Richards–Darcy equation more precisely by determining the root water uptake value.

Natural superabsorbent plastic materials based on a functionalized soy protein

A natural superabsorbent polymer (SAP) material based on an acylated soy protein was studied as a green alternative to non-biodegradable SAP. In order to obtain the natural SAPs, different amounts of succinic anhydride were used as acylating agent. Once the functionalized protein was obtained, it was mixed thoroughly with glycerol and then molded through a lab-scale injection molding device. Water uptake of samples obtained reached values much higher than those based on unacylated protein. Moreover, a greater extent of the acylation reaction led to higher water uptake values for the corresponding SAPs, probably related to their higher hydrophilic character. Water imbibing capacity measurements and thermogravimetrical analysis (TGA) seemed to confirm this. The presence of larger porous regions in acylated samples observed in SEM images could also play a role in their higher water uptake values.Furthermore, an increase in the extent of acylation reaction led to plastics with lower Young's modulus and higher extensibility.

Computed tomography–based quantification of lesion water uptake identifies patients within 4.5 hours of stroke onset: A multicenter observational study

Many patients with stroke cannot receive intravenous thrombolysis because the time of symptom onset is unknown. We tested whether computed tomography (CT)-based quantification of water uptake in the ischemic tissue can identify patients with stroke onset within 4.5 hours, the time window of thrombolysis. Perfusion CT was used to identify ischemic brain tissue, and its density was measured in native CT and related to the density of the corresponding area of the contralateral hemisphere to quantify lesion water uptake. The optimal cutoff value of water uptake distinguishing stroke onset within and beyond 4.5 hours was calculated in patients with proximal middle cerebral artery occlusion (derivation cohort) with known time of symptom onset. The so-derived cutoff value was validated in a prospective cohort from other stroke centers. Of 178 patients of the derivation cohort, 147 (82.6%) had CT within 4.5 hours. Percentage water uptake was significantly lower in patients with stroke onset within compared to beyond 4.5 hours. The area under the receiver operating characteristic curve for distinguishing these patient groups according to percentage water uptake was 0.999 (95% confidence interval = 0.996-1.000, p < 0.001) with an optimal cutoff value of 11.5%. Applying this cutoff to the validation cohort of 240 patients, sensitivity was 98.6%, specificity 90.5%, positive predictive value 99.1%, and negative predictive value 86.4%. Quantification of brain water uptake identifies stroke patients with symptom onset within 4.5 hours with high accuracy and may guide the decision to use thrombolysis in patients with unknown time of stroke onset. Ann Neurol 2016;80:924-934.

Molecular dynamics study of confined structure and diffusion of hydrated proton in Hyfion® perfluorosulfonic acid membranes

In polyelectrolyte membranes, hydrated protons and proton conductive channels have cooperative effect on proton conductivity, the mechanism of which is believed to involve the structure of hydrated proton being deformed to adapt the confining channel. To investigate the dependence of the structural and dynamical properties of hydrated protons in Hyfion® perfluorosulfonic acid membranes with various water uptake values on the channel size, a series of molecular dynamics simulations based on an all-atom force field were conducted. The water uptake dependence of the hydrated proton diffusivity determined from our simulations was consistent with the experimental results in literature, which verified the simulation systems. A probability distribution of the hydrated proton complex is proposed to characterize the confinement effect of the proton conductive channel on the hydrated proton structure in the membranes with different morphologies. By means of local structural properties and pair-potential energies, a reasonable hydrogen bond criterion was employed to characterize the structures of the hydrated proton complexes. It was found that the nanochannels confined the structure of the hydrated proton complex and that confined complexes of H9O4+, H7O3+ and H5O2+ were dominant. Weakening the confinement by increasing the channel size was beneficial for the formation of the H9O4+ complex, the probability distribution of which gradually became plateau. Thus, H9O4+ can be considered the stable structure of the confined hydrated proton complex in polymer electrolyte membranes. This work is helpful in understanding the relationship between the structure of the confined hydrated proton and the proton conductive channel. It also provides potential guidance for improving the membrane performance in fuel cell.

Production of lactobionic acid by BMED process using porous P84 co-polyimide anion exchange membranes

Abstract Porous P84 co-polyimide anion exchange membranes are prepared by phase inversion process using isopropanol (IPA) or water as the non-solvent. Membrane area resistances are in the range of 0.7–2.2 Ω cm2, lower than those of commercial anion exchange membrane AMX (2.0–3.5 Ω cm2) and dense P84 membrane (>80 Ω cm2). The ion exchange capacities (IECs) are in the range of 0.6–0.9 mmol/g and the water uptake (WR) values are 100–160%, both of which are higher than those of dense P84 membrane. The porous P84 co-polyimide membranes are utilized in bipolar membrane electrodialysis (BMED) process to produce lactobionic acid (LBA) and NaOH from sodium lactobionic. The pore morphology and IECs influence the output of LBA significantly. Membrane with big tear-like pores shows higher WR value and can produce 0.0555–0.0565 mol/L LBA. Sponge-like pores with IEC of 0.9 mmol/g can yield 0.0724 mol/L LBA after 180 min running under 20 V, while sponge-like pores with IEC of 0.7 mmol/g yield reduced LBA concentration of 0.0593 mol/L, illustrating that higher IEC is in favour of the passage of LB−. The porous P84 membranes have improved efficiency as compared with commercial membrane AMX (0.0451 mol/L) and the dense P84 membrane (merely 0.0162 mol/L) in the production of LBA. Meanwhile, the Na+ leakage through the porous membrane is similar to that of the commercial membrane. Hence, the porous membranes, due to their low resistances, can have high potential for producing organic acid with high molecular weight.