Membrane Properties Research Articles

Anti‐fouling capacity enhancement of thin‐film composite polyamide membrane by chitosan graft polymerization methods

AbstractThis study aimed to improve the anti‐fouling properties of a thin‐film composite polyamide membrane by modifying it with chitosan and acrylic acid using UV‐induced and Redox‐initiated graft polymerization methods. The modified membrane's separation performance was evaluated by measuring the flux and retention of sodium ions in water during filtration. The anti‐fouling capacities of the modified membranes were determined by measuring the maintained flux ratios and irreversible fouling factors during the 8‐h filtration of aqueous solutions of sodium chloride at different concentrations (1000 and 10,000 ppm). In addition, by evaluating the membrane's surface properties using various methods, including field emission scanning electron microscopy, attenuated total reflection – Fourier transform infrared spectroscopy, and water contact angle measurements, we have demonstrated the validity of the experimental results. Our results showed that the grafted membranes under UV irradiation or redox initiators had enhanced anti‐fouling properties while maintaining salt retention. The modified membranes fabricated by UV‐induced or Redox‐initiated technique had superior anti‐fouling capabilities, with irreversible fouling factors and maintained flux ratios of around 8% and 43%, respectively, after 8 h of filtration, compared to only 12% and 36% for the unmodified membrane. These findings suggest that the modified membranes have the potential for use in filtration systems to prevent the fouling phenomenon.

Mercaptoethanol-assisted synthesis of sulfonic acid-functionalized polysiloxanes as inorganic fillers in composite membranes for energy-storage applications

Developing proton-exchange membranes (PEMs) for energy applications is necessary for fulfilling the increasing energy demand without environmental effects. In this study, we prepared composite membranes containing mercaptoethanol-assisted sulfonic acid-functionalized polysiloxanes (MASFPs) and perfluorinated sulfonic acid (PFSA). The MASFP-containing composite membrane (i.e., CMASFP-2) exhibited better membrane properties than the composite membrane prepared without mercaptoethanol (CMASFP-1) and the reference Nafion 212 membrane. Wide-angle X-ray diffraction (XRD) studies revealed a broad peak at 2θ = 17.4° and 39°, indicating that the composite membranes are semicrystalline. Scanning electron microscopy (SEM) analysis revealed that the prepared composite membranes had good morphology, whereas energy-dispersive X-ray spectroscopy analysis revealed that it had siloxane and more sulfonic acid than the pristine PFSA membrane. Thermogravimetric and mechanical strength analyses revealed that incorporating sulfonic acid-functionalized siloxanes improved the thermal stability and mechanical strain of the membrane. The prepared CMASFP-2 membrane had a high ionic conductivity of 0.106 mS cm−1 and an ion-exchange capacity of 1.09 meq·g−1. CMASFP-2 also exhibited lower hydrogen gas permeability than the Nafion 212 and PFSA membranes, demonstrating that it can be used for energy applications.

Shades of gravity - effects of planetary gravity levels on electrocortical activity and neurocognitive performance.

The plans of international space agencies to return to the Moon and explore deep space, including Mars, highlight the challenges of human adaptation and stress the need for a thorough analysis of the factors that facilitate, limit and modify human performance under extreme environments. This study investigates the influence of partial gravity on behavioural (error rate and reaction time) and neuronal parameters (event-related potentials) through parabolic flights. Brain cortical activity was assessed using EEG from 18 participants who solved a neurocognitive task, consisting of a mental arithmetic task and an auditory oddball paradigm, during Earth (1G), Lunar (0.16G + 0.25G) and Martian gravity (0.38G + 0.5G) for 15 consecutive parabolas. Data shows higher electrocortical activity in Earth gravity compared to Lunar and Martian gravity in the parietal lobe. No differences in participants' performance were found among the gravity levels. Event-related potentials displayed gravity-dependent variations, though limited stimuli recording suggests caution in interpretation. Data suggests a threshold between Earth and Martian gravity within the different gravities responsible for physiological changes, but it seems to vary greatly between individuals. The altered neuronal communication could be explained with a model developed by Kohn and Ritzmann in 2018. The increasing intracranial pressure in weightlessness changes the properties of the cell membrane of neurons and leads to a depolarisation of the resting membrane potential. The findings underscore the individuality of physiological changes in response to gravity alterations, signalling the need for further investigations in future studies.

The influence of the hydrogenation process on the microstructure and properties of metallic materials

Hydrogen, which belongs to the group of the smallest elements, can freely penetrate the structure of metallic materials and cause enormous damage. This phenomenon may occur due to various conditions and may have different effects on the properties of materials. Understanding these mechanisms is important in the era of changing to alternative energy sources. This situation may occur in combustion engines powered by hydrogen-enriched fuel. The work analyzed the impact of various hydrogenation processes on the properties of aesthetic steel, which is allergic to the formation of carbides at the grain boundaries, such a microstructure is intended to simulate the least favorable working conditions. The work was aimed at evaluating the effects of different hydrogenation methods on changes in the properties of the AISI 310s steel membrane. In the work, electrolytic hydrogenation and heat treatment procedures in a hydrogen atmosphere were used. Investigations of changes in material properties included microhardness and in-situ strength tests in a scanning electron microscope chamber. Research has shown that both processes increase the hardness of materials and change the characteristics of stretching curves.

Fluorescence lifetime imaging microscopy of flexible and rigid dyes probes the biophysical properties of synthetic and biological membranes

Sensing of the biophysical properties of membranes using molecular reporters has recently regained widespread attention. This was elicited by the development of new probes of exquisite optical properties and increased performance, combined with developments in fluorescence detection. Here, we report on fluorescence lifetime imaging of various rigid and flexible fluorescent dyes to probe the biophysical properties of synthetic and biological membranes at steady state as well as upon the action of external membrane-modifying agents. We tested the solvatochromic dyes Nile red and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl) (ammonium salt), the viscosity sensor Bodipy C12, the flipper dye FliptR, as well as the dyes 3,3′-dioctadecyloxacarbocyanine perchlorate, Bodipy C16, lissamine-rhodamine, and Atto647, which are dyes with no previous reported environmental sensitivity. The performance of the fluorescent probes, many of which are commercially available, was benchmarked with the well-known environmental reporters, with Nile red and Bodipy C12 being specific reporters of medium hydration and viscosity, respectively. We show that some widely used ordinary dyes with no previous report of sensing capabilities can exhibit competing performance compared to highly sensitive commercially available or custom-based solvatochromic dyes, molecular rotors, or flipper in a wide range of biophysics experiments. Compared to other methods, fluorescence lifetime imaging is a minimally invasive and nondestructive method with optical resolution. It enables biophysical mapping at steady state or assessment of the changes induced by membrane-active molecules at subcellular level in both synthetic and biological membranes when intensity measurements fail to do so. The results have important consequences for the specific choice of the sensor and take into consideration factors such as probe sensitivity, response to environmental changes, ease and speed of data analysis, and the probe’s intracellular distribution, as well as potential side effects induced by labeling and imaging.

Piperidinium-Incorporated Fabrication of High-Performance Polyamide Nanofiltration Membrane with High Free Volume for Magnesium/Lithium Separation

Efficient magnesium-lithium separation is key to extracting lithium resources from salt lake brines. However, efficient magnesium-lithium separation is constrained by the high magnesium-to-lithium ratios on the nanofiltration separation performance due to weakened Donnan effect and inherent permeability-selectivity trade-off behaviour. To address this challenge, a dual methylpiperidinium ion liquid was designed in this work and incorporated into polyamide networks to manipulate the structural properties of polyamide networks membrane for improved magnesium/lithium separation. We demonstrate that the piperidinium modification of polyamide networks not only modulated and enhanced the morphology, hydrophilicity, free volume and electropositivity but also synergized the steric hinderance differentiation inside the membrane nanochannels. These structural advantages enabled the modified membrane to achieve high-separation performance with enhanced water permeance of 37.3 L m−2 h−1 bar−1 and Mg2+/Li+ selectivity of 30.6 (for Mg/Li mass ratio of 31.2). Molecular dynamics simulations further confirmed that the fast water transport and the difference in the ion separation behaviour is strongly correlated to the enhanced structural properties of membranes. We expect this work to provide insightful guidance for engineering high-performance membranes and make contributions in the application of nanofiltration in lithium mining from high Mg/Li ratio brines.

Carrageenan/calcium alginate composite hydrogel filtration membranes for efficient cationic dye separation

The development of biopolymer-based filtration systems for water remediation applications is an extremely fascinating area of research. In this paper, we developed a biopolymer-based filtration system using sodium alginate (NaAlg) and carrageenan (Car) for the removal of the toxic cationic dye, methylene blue (MB). The membrane's properties were assessed using FTIR, TGA, UTM, FESEM, EDS, XRD, and water uptake, revealing commendable thermomechanical stability (5.79 MPa), good hydrophilicity, and compatibility. The experimental results further revealed that lambda Car/calcium alginate (λ-Car/CaAlg) exhibited superior dye rejection (100 %) and flux (11.67 L m−2 h−1) compared to kappa Car/CaAlg (κ-Car/CaAlg) (99.22 % and 11.19 L m−2 h−1) and plain alginate (CaAlg) (99.63 % and 9.79 L m−2 h−1). The high MB rejection rate was attributed to the sieving mechanism and electrostatic interaction. A rejection rate of 100 % was achieved at an initial MB concentration of 10 mg/L, pressure of 0.1 MPa, pH of 7, and temperature of 25 °C. Furthermore, the hydrogel membranes demonstrated excellent recyclability over nine cycles, indicating their potential for water treatment applications.

Molecular dynamics simulations of lipid-protein interactions in SLC4 proteins

The SLC4 family of secondary bicarbonate transporters is responsible for the transport of HCO3¯, CO32¯, Cl¯, Na+, K+, NH3 and H+ necessary for regulation of pH and ion homeostasis. They are widely expressed in numerous tissues throughout the body and function in different cell types with different membrane properties. Potential lipid roles in SLC4 function have been reported in experimental studies, focusing mostly on two members of the family: AE1 (Cl¯/HCO3¯ exchanger) and NBCe1 (Na+-CO32¯cotransporter). Previous computational studies of the outward facing (OF) state of AE1 with model lipid membranes revealed enhanced protein-lipid interactions between cholesterol (CHOL) and phosphatidylinositol bisphosphate (PIP2). However, the protein-lipid interactions in other members of the family and other conformation states are still poorly understood and this precludes the detailed studies of a potential regulatory role for lipids in the SLC4 family. In this work, we performed coarse-grained and atomistic molecular dynamics simulations on three members of the SLC4 family with different transport modes: AE1, NBCe1 and NDCBE (a Na+-CO32¯/Cl¯ exchanger), in model HEK293 membranes consisting of CHOL, PIP2, phosphatidylcholine (POPC), phosphatidylethanolamine (POPE), phosphatidylserine (POPS), and sphingomyelin (POSM). The recently resolved inward-facing (IF) state of AE1 was also included in the simulations. Lipid-protein contact analysis of the simulated trajectories was performed with the ProLint server, which provides a multitude of visualization tools for illustration of areas of enhanced lipid-protein contact and identification of putative lipid binding sites within the protein matrix. We observed enrichment of CHOL and PIP2 around all proteins with subtle differences in their distribution depending on the protein type and conformation state. Putative binding sites were identified for CHOL, PIP2, POPC, and POSM in the three studied proteins and their potential roles in the SLC4 transport function, conformational transition and protein dimerization were discussed.

Characterization of electrokinetic and membrane properties of nanoporous polyimide films via measurements of time-resolved pressure-induced potential

Charged nanoporous films have interesting ion-separation properties essentially controlled by pore-surface charge density. This (or a related zeta-potential) is often estimated from the so-called streaming potential. However, with nanoporous membranes in sufficiently dilute electrolyte solutions, the pressure-induced electrical response is due not only to streaming potential but also to an electrical response to concentration gradients arising because of a partial salt rejection by charged nanopores. In this study, we refine the methodology of interpretation of measurements of transient filtration potential developed by us previously and apply it to the determination of electrokinetic and membrane properties (in particular, diffusion permeance) of nanoporous polyimide films developed for uses as battery/supercapacitor separators. Diffusion permeance is directly related to electrical conductance, which is an important property of battery/supercapacitor separators.We observe that in dilute electrolyte solutions (<2 mM KCl), the electrical response to an applied pressure difference is dominated by the concentration potential and not by the classical streaming potential contrary to what is often tacitly assumed. The development of concentration gradients across and around the film takes some time, which enables separate determination of instantaneous (streaming potential) and time-delayed (concentration potential) components. An improved interpretation procedure developed in this study enables estimates of impact of non-linear and osmotic corrections and makes the interpretation more reliable. The results of this study are important for the identification and optimization of novel innovative applications for nanoporous films.

Enhanced resistance of PdNiAu membranes under CO and H2S-containing streams

Pd-based membranes offer energy efficiency and economic advantages, providing a promising route for hydrogen separation and recovery from several streams. Alloying Pd with other elements increases its resistance to corrosive gases while improving H2 permeability. This study investigated the permselective properties of PdNiAu membranes with different Ni contents (17, 23, and 27 at.% Ni) in pure H2 and under CO/He/H2 and H2S/H2 mixtures. The permselective properties were evaluated at different temperatures (573-723 K) and pressure differences across the membrane (ΔP: 10-100 kPa). The membranes studied exhibited promising H2 permeation properties; the highest permeability at 673 K and 100 kPa was obtained with the membrane containing 23 at.% Ni (2.1 x10-8 mol m-1 s-1 Pa-0.5). All membranes exhibited high H2/N2 selectivity (>10,000). Regarding chemical stability, the membranes with 23 and 27 at.% Ni, showed high tolerance to inhibition by CO and H2S. These results suggest that increasing Ni improves membrane performance in streams containing CO or S; however, the high chemical resistance of the membranes could be attributed to both Ni and Au.

Vibration of microphone membrane: Effects of thermal stress

The aim of this work is to improve theoretical and experimental tools for modelling and characterising the global behaviour of measurement microphones in a large range of environmental conditions. In most of measurement microphones, the sensitive part is a vibrating membrane stretched and clamped on the body of the microphone. If the sensor is operated at ambient temperatures that significantly differ from atmospheric one, thermal expansion of the microphone membrane and body causes strain and stress variations in the membrane, which lead to altered vibrational behaviour when it is submitted to an acoustic wave. An analytical approach is developed here to express the thermal stress related to the fact that thermal expansions of the microphone membrane and body are different. These effects are then taken into account in a classical modelling procedure for describing the vibration of a microphone membrane in vacuo. An experiment, that relies on the electrostatic actuator technique, has been performed in a fine vacuum to characterise the first resonance mode of a commercial microphone membrane in low temperatures range, from atmospheric to cryogenic. The experimental results highlight the significant effects of the thermal stress induced by the differences between thermal expansion properties of the materials constituting the microphone. These results are consistent with the membrane vibration predicted by the analytical modelling proposed. Thus, even small differences between the thermal expansion properties of the microphone membrane and body have to be taken into account in a modelling procedure to get reliable predictions of the membrane vibration at various ambient temperatures.

Self-adhesive and firm zein fibrous membrane via eugenol-induced dynamic molecular regulation for water treatment

Zein fibrous membrane is a good choice for wastewater treatment owing to abundant functional groups, nontoxicity and degradability. However, zein-based fibrous membrane usually suffers from poor durability due to poor mechanical properties. Traditional methods for improving the mechanical properties often face inevitably challenges, such as operational complexity, environmental pollution and interface delamination. Herein, a simple, green and effective strategy of Eugenol induced “dynamic switch” is proposed to enhance the mechanical properties of zein fibrous membrane. This method alters the molecular conformation and solvent volatility, which enhances the spinnability, forms fiber self-adhesion and tight adhesion to the substrate. The mechanical properties of zein fibrous membranes improves 4.4 times compared with original zein fibrous membrane, and exhibits good applications in water treatment. Additionally, it is universal to various substrates and ethanol–water solvent-based spinning solution. This “dynamic switch” strategy enables zein fibrous membrane firm and self-adhesive via a cost-effective, time-efficient, eco-friendly and widely universal fabrication, which provides potential broad applications for zein-based membrane materials.

Side-chain type PPO based anion exchange membrane with steric hindrance containing dual conduction sites

Appropriate addition of cation transport sites while maintaining the good mechanical properties of anion exchange membranes (AEMs) can effectively improve the hydroxide ion conductivity. Therefore, a series of poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) based side-chain type AEMs containing dual conduction sites are successfully prepared. The 4-(4-dimethylaminostyryl)-1-methylpyridinium (DASP) side chains are grafted to brominated PPO at different ratios, which is confirmed by Fourier transform infrared spectroscopy (FT-IR). Analysis of the microscopic morphology reveals a distinct microscopic separation pattern of hydrophilic/hydrophobic regions, which provides efficient channels for the transport of hydroxide ions. The ionic conductivity of the PPO-DASP13 membrane reaches 89.97 mS/cm at 80 °C, which is benefited from the double cationic groups contained in the side chains, providing more conduction sites for hydroxide ions. Meanwhile, the tensile strength of membranes range from 17.83 MPa to 29.38 MPa, which have good mechanical properties. The ionic conductivity of all membranes retain about 70% after a 800 h long-term alkali resistance test, which is related to the steric hindrance contained in the side chain structure and the conjugated system. Furthermore, the single cell based on PPO-DASP13 membrane with the highest ionic conductivity achieves a peak power density of 347.7 mW/cm2 in H2-air (CO2-free) at 60 °C.

Lithium extraction from salt lake brine by four-stage ion-distillation of flow electrode capacitive deionization

Herein, a novel, highly efficient, and low-energy consumption four-stage ion-distillation of FCDI (ID-FCDI) device was developed that combined four commercial monovalent selective membranes with four flow electrode channels for high selectivity to extract Li+ ions from salt lake. It exhibited excellent separation factor (SMg2+Li+ = 11247.27), high enrichment ratio (4.95 times), super purity of Li+ ion solution (99.97 %), and low molar energy consumption (Em = 0.21 kWh mol−1) at mass ratio of Mg2+/Li+ = 1:1. The mathematical model calculation revealed that the excellent selective separation effectiveness of the as-proposed ID-FCDI system is due to the unique property of the monovalent selectivity membranes, in which the transmembrane rate of lithium ions is ten times that of magnesium ions under the same condition. Furthermore, the separation mechanism of the as-proposed ID-FCDI device for Li+/Mg2+ ions was determined by the high electrosorption capacity of the flow electrode for Li+ ions (1.14 times higher than Mg2+ ions), low diffusion resistance (1.413 Ω), and high diffusion coefficient of Li+ ions (2.83 times faster than Mg2+ ions) by electrochemical measurement. On this basis, 3.92 times of lithium was successfully enriched in the natural salt lake brine of Golmud (mass ratio of Mg2+/Li+ = 79.29), and the separation factor was 6307.17 with a 99.64 % purity of Li+ ion solution and an Em of 0.20 kWh mol−1. Finally, the Li2CO3 product (99.66 %) was precipitated via the reaction between Na2CO3 and the enriched Li+ ion solution, consequently fulfilling the battery-level application of the industrial purity requirements. These findings highlight that this device is promising and profitable for lithium extraction from salt lake in industrial production.

Porous silicate cement membrane: unraveling the effect of triethanolamine on ice crystal changing, pore structure, and performance

Triethanolamine (TEA) has been broadly used as the organic amine conditioning agent to modify the workability of cement-based materials. However, the effect of TEA on the structure and property of porous silicate cement membranes has not been reported. In this paper, TEA was applied to study its effect on parameters of porous silicate cement membranes based on the preparation method combining freeze casting and heat-dry curing, because it is easy to form complexes with cement particles. The effect and acting mechanism of TEA on porous silicate cement membranes were researched using a series of characterizations and molecular dynamics (MD) simulation. Results showed that TEA significantly improved the performance of porous silicate cement membranes. The addition of TEA changed the pore morphology of porous silicate cement membranes from lamellar structures to cellular structures, with mesoporous size distribution focusing on 2.5 ∼ 4.5 nm at TEA doping ratio of 0.16 wt.%. The oil-water separation performance could reach up to 99.6%. Through comprehensive comparison, the porous silicate cement membrane with 1.0 wt.% TEA showed better holistic preponderance of oil-water separation and permeation flux. Quantum chemistry calculation and MD simulation were used to briefly explain the influence of TEA on phase transformation. MD showed that adding TEA changed the morphology and structure of ice crystals. The percentage of the Ih structure significantly increased from 53% to 86% after adding TEA. This study might expand the application of TEA in other aspects and enlighten relevant workers in new experimental designs.

Coordination of bilayer properties by an inward-rectifier K+ channel is a cooperative process driven by protein-lipid interaction

Physical properties of biological membranes directly or indirectly govern biological processes. Yet, the interplay between membrane and integral membrane proteins is difficult to assess due to reciprocal effects between membrane proteins, individual lipids, and membrane architecture. Using solid-state NMR (SSNMR) we previously showed that KirBac1.1, a bacterial Inward-Rectifier K+ channel, nucleates bilayer ordering and microdomain formation through tethering anionic lipids. Conversely, these lipids cooperatively bind cationic residues to activate the channel and initiate K+ flux. The mechanistic details governing the relationship between cooperative lipid loading and bilayer ordering are, however unknown. To investigate, we generated KirBac1.1 samples with different concentrations of 13C-lableded phosphatidyl glycerol (PG) lipids and acquired a full suite of SSNMR 1D temperature series experiments using the ordered all-trans (AT) and disordered trans-gauche (TG) acyl conformations as markers of bilayer dynamics. We observed increased AT ordered signal, decreased TG disordered signal, and increased bilayer melting temperature with increased PG concentration. Further, we identified cooperativity between ordering and direct binding of PG lipids, indicating KirBac1.1-driven bilayer ordering and microdomain formation is a classically cooperative Hill-type process driven by and predicated upon direct binding of PG lipids. Our results provide unique mechanistic insight into how proteins and lipids in tandem contribute to supramolecular bilayer heterogeneity in the lipid membrane.

The Superior Electrochemical Property of LiTFSI@(Ba+Nb)-co-doped Li7La2.75Ba0.25Zr1.75Nb0.25O12@PEO Composite Membrane in All-Solid-State Lithium Battery

It is popular to choose the cubic phase Li7La3Zr2O12(c-LLZO) to synthesize the PEO-based complex membrane in all-solid-state battery. In this work, Ba/Nb elements were selected to achieve Li6.75La3Zr1.75Nb0.25O12 (LLZNO) and Li7La2.75Ba0.25Zr1.75Nb0.25O12 (LLBZNO) with high ion conductivity, which effectively enhance the electrochemical properties of the complex solid membrane and the all-solid-state battery. The higher ion mobility of LLBZNO compared to that of LLZNO and LLZO is calculated by ab-initio molecular dynamics (AIMD) simulation and further confirmed by experiments. Results show that the cubic phase of LLBZNO is more stable than that of LLZNO. The complex membrane of LLBZNO@ polyethylene oxide (PEO) (CPE-2-x wt%) exhibits the better electrochemical properties than LLZNO@PEO (CPE-1-x wt%) complex membrane. In detail, the CPE-2–10 wt% has the outstanding lithium transfer number ( tLi+ ) of 0.63, as well as the excellent compatibility with lithium metal anode. In addition, at 0.1 mA∙cm−2, the lithium/CPE-2–10 wt%/lithium symmetric cell remains stable after 1000 h. It is LLBZNO that makes LLBZNO@PEO composite polymer electrolyte(CPE) the potential for the application in all-solid-state lithium battery.

The effect of the number of sulfonic acids in polysiloxanes as fillers for polymer electrolyte membranes in energy storage applications

A series of sulfonic acid-functionalized polysiloxanes (MASFPs) that can be used to reduce the cost and improve the properties of proton exchange membranes (PEMs) by acting as fillers have been synthesized. In this paper, we describe the synthesis of MASFPs with varying numbers of sulfonic acid groups with the aid of mercaptoethanol. An array of analytical techniques were employed to characterize the synthesized MASFPs. The broad peak observed in the X-ray diffraction pattern of MASFPs between 2θ = 15–25° signifies their amorphous characteristics. Analyses by infrared spectroscopy also identify MASFPs that contain stretching vibrations for –SO3H, –CH2, and Si–O– group. The thermogravimetric analysis demonstrates the thermal stability of these MASFPs. The surface morphology analysis of the MASFPs using FESEM and HRTEM revealed the presence of spherical particles that exhibited significant aggregation and distortion. By employing X-ray photoelectron spectroscopy (XPS) to determine the atomic weight percentage of sulfur present in the MASFPs, the number of sulfonic acids contained within was verified. The sulfur content of MASFPs is determined by XPS to be as follows: MASFP-4 > MASFP-3 > MASFP-2 > MASFP-1. The presence of Q4, Q3, T3, and T2 signals, as determined by 29Si MAS NMR analysis, confirms the polysiloxane formation. Preliminary studies of the composite membrane prepared using the MASFPs with perfluorosulfonic acid (PFSA:MASFP in 75:25 ratio) exhibited superior ionic conductivity (0.102 S/cm) and ion-exchange capacity (1.16 meq/g) in comparison to the commercial Nafion membrane. Overall, using a mercaptoethanol-assisted process to synthesize sulfonic acid functionalized polysiloxanes is an excellent way to increase the incorporation of sulfonic acids and it can be applied to the synthesis of various other inorganic nanofillers.

Cosolvent-assisted construction of high-performance reverse osmosis membranes with multilayer nanovoid structures: Effect of amides in aqueous phase

The cosolvent-assisted interfacial polymerization (CAIP) has garnered significant attention due to its capacity to easily and effectively modify the performance of polyamide (PA) reverse osmosis (RO) membranes. To gain deeper understanding of the mechanism of a specific type of cosolvents on the IP reaction, namely N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N,N-dimethylpropionamide (DMPr) were used as aqueous-phase cosolvents to systematically investigate their effects on the membrane structures and properties under different conditions. Amide cosolvents in the aqueous phase facilitated the diffusion of the amine monomer and the formation of nanovoids within the PA layer as the C-chain length of amides increased. When 1,2-dichloroethane was also included in the organic phase, the extent of the two-phase miscible zone was further increased with its assistance, which contributed to generating the larger nanovoids within the layer, thicker PA layer and extensive exterior PA layers, as well as significantly enhancing the water permeability and selectivity of membranes. Importantly, this study successfully prepared high-performance RO membranes with multilayer nanovoid structures in situ by introducing cosolvents in the IP reaction with permeability up to 2.26 L·m−2·h−1·bar−1, providing theoretical and experimental bases for further enrichment of CAIP.

HIV and influenza fusion peptide interactions with (dis)ordered lipid bilayers: Understanding mechanisms and implications for antimicrobial and antiviral approaches

The study investigates the interactions of viral fusion peptides from influenza (E4K and Ac-E4K) and human immunodeficiency virus (gp41 and Ac-gp41) with planar lipid bilayers. A combination of surface-sensitive techniques, including quartz crystal microbalance with dissipation (QCM-D), Langmuir area-pressure isotherms with Micro-Brewster angle microscopy, and neutron reflectometry, was employed. Differences in the interactions of the viral fusion peptides with lipid bilayers featuring ordered and disordered phases, as well as lipid rafts, were revealed. The HIV fusion peptide (gp41) exhibited strong binding to the DOPC/DOPS bilayer, comprising a liquid disordered phase, with neutron reflectometry (NR) showing interaction with the bilayer's headgroup area. Conversely, negligible binding was observed with lipid bilayers in a liquid ordered phase. Notably, the influenza peptide (E4K) demonstrated slower binding kinetics with DOPC/DOPS bilayers and distinct interactions compared to gp41, as observed through QCM-D. This suggests different mechanisms of interaction with the lipid bilayers: one peptide interacts more within the headgroup region, while the other is more involved in transmembrane interactions. These findings hold implications for understanding viral fusion mechanisms and developing antimicrobials and antivirals targeting membrane interactions. The differential binding behaviours of the viral fusion peptides underscore the importance of considering membrane composition and properties in therapeutic strategy design