Membrane Mechanical Properties Research Articles

Covalently attached phosphonic acid‐Si2O3‐PEO polymer membranes for PEMFC applications

AbstractIn the context of growing interest in phosphonic acid proton exchange membranes (PEMs) for fuel cell applications, we report on new PEMs containing low‐cost polyethylene oxide (PEO) covalently linked by siloxane bonds, SiOSi, to phosphonic acid (PA). Key chemistry in the formation of these membranes involves hydrolysis and condensation reactions of triethoxysilyl propyl capped PEO and pre‐hydrolyzed dimethyl phosphonatoethyltrimethoxysilane (DMPTMS) giving PEO‐Si2O3‐PA and cross‐linked chain PEO‐Si2O3‐PEO organosilsesquioxane components. The Si2O3 can enhance membrane thermal and mechanical properties. The membrane formulations were varied by (a) reagent ratios (b) PEO molecular weights or using polypropylene oxide (PPO) (c) incorporating chain extending groups methylene diphenyl diisocyanate (MDI) or hexamethylene diisocyanate (HDI). These variations provided five membrane families, one of which afforded a complete group of robust membranes with weight% x of PA, PAx in range PA0–PA33. These were studied using ATR‐FTIR, dry membrane water uptake capacity, ion exchange capacity (IEC), and conductivity from room temperature to 120°C at 100% relative humidity. Conductivity increased with PAx reaching 15 mS cm−1 at 120°C, activation energy 0.1 eV, for membrane PA33 for which thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and energy dispersive X‐ray analysis (EDAX) are reported. A comparative performance of the five membrane families is presented.

Tunneling nanotubes mediate KRas transport: Inducing tumor heterogeneity and altering cellular membrane mechanical properties

Mutation in oncogene KRas plays a crucial role in the occurrence and progression of numerous malignant tumors. Malignancy involves changes in cell mechanics for extensive cellular deformation during metastatic dissemination. We hypothesize that oncogene KRas mutations are intrinsic to alterations in cellular mechanics that promote malignant tumor generation and progression. Here, we demonstrate the use of optical tweezers coupled with a confocal fluorescence imaging system and gene interference technique to reveal that the mutant KRas protein can be transported between homogeneous and heterogeneous tumor cells by tunneling nanotubes (TNTs), resulting in a significant reduction of membrane tension and acceleration of membrane phospholipid flow in the recipient cells. Simultaneously, the changes in membrane mechanical properties of the tumor cells also enhance the metastatic and invasive ability of the tumors, which further contribute to the deterioration of the tumors. This finding helps to clarify the association between oncogene mutations and changes in the mechanical properties of tumor cells, which provides a theoretical basis for the development of cancer treatment strategies. Statement of significanceHere, we present a laser confocal fluorescence system integrated with optical tweezers to observe the transfer of mutant KRasG12D protein from mutant cells to wild-type cells through TNTs. Malignancy involves changes in cell mechanics for extensive cellular deformation during metastatic dissemination. Our results demonstrate a significant decrease in membrane tension and an increase in membrane phospholipid flow in recipient cells. These alterations in mechanical properties augment the migration and invasive capabilities of tumor cells, contributing to tumor malignancy. Our findings propose that cellular mechanical properties could serve as new markers for tumor development, and targeting membrane tension may hold potential as a therapeutic strategy.

Isoporous Membranes by the Symmetric Triblock Copolymer: A Strategy to Improve the Mechanical Strength without Sharply Changing the Pore Size and Permselectivity.

Isoporous membranes produced from diblock copolymers commonly display a poor mechanical property that shows many negative impacts on their separation application. It is theoretically predicted that dense films produced from symmetric triblock copolymers show much stronger mechanical properties than those of homologous diblock copolymers. However, to the best of our knowledge, symmetric triblock copolymers have rarely been fabricated into isoporous membranes before, and a full understanding of separation as well as mechanical properties of membranes prepared from triblock copolymers and homologous diblock copolymers has not been conducted, either. In this work, a cleavable symmetric triblock copolymer with polystyrene as the side block and poly(4-vinylpyridine) (P4VP) as the middle block was synthesized and designed by the RAFT polymerization using the symmetric chain transfer agent, which located at the center of polymer chains and could be removed to produce homologous diblock copolymers with half-length while having the same composition as that found in triblock copolymers. The self-assembly of these two copolymers in thin films and casting solutions was first investigated, observing that they displayed similar self-organized structures under these two conditions. When fabricated into isoporous membranes, they showed similar pore sizes (5-7% difference) and comparable rejection performance (∼10% difference). However, isoporous membranes produced from triblock copolymers showed significantly improved mechanical strength and higher toughness (2-10 times larger) as evidenced by the compacting resistance, strain-stress determination, and nanoindentation testing, suggesting the unique and novel structure-performance relationship in the isoporous membranes produced from symmetric triblock copolymers. The above finding will guide the way to fabricate mechanically robust isoporous membranes without notably changing the separation performance from rarely used symmetric triblock copolymers, which can be synthesized by the controlled polymerization as facilely as that found for diblock copolymers.

Tailoring silk fibroin fibrous architecture by a high-yield electrospinning method for fast wound healing possibilities.

In this study, a novel array electrospinning collector was devised to generate two distinct regenerated silk fibroin (SF) fibrous membranes: ordered and disordered. Leveraging electrostatic forces during the electrospinning process allowed precise control over the orientation of SF fiber, resulting in the creation of membranes comprising both aligned and randomly arranged fiber layers. This innovative approach resulted in the development of large-area membranes featuring exceptional stability due to their alternating patterned structure, achievable through expansion using the collector, and improving the aligned fiber membrane mechanical properties. The study delved into exploring the potential of these membranes in augmenting wound healing efficiency. Conducting in vitro toxicity assays with adipose tissue-derived mesenchymal stem cells (AD-MSCs) and normal human dermal fibroblasts (NHDFs) confirmed the biocompatibility of the SF membranes. We use dual perspectives on exploring the effects of different conditioned mediums produced by cells and structural cues of materials on NHDFs migration. The nanofibers providing the microenvironment can directly guide NHDFs migration and also affect the AD-MSCs and NHDFs paracrine effects, which can improve the chemotaxis of NHDFs migration. The ordered membrane, in particular, exhibited pronounced effectiveness in guiding directional cell migration. This research underscores the revelation that customizable microenvironments facilitated by SF membranes optimize the paracrine products of mesenchymal stem cells and offer valuable physical cues, presenting novel prospects for enhancing wound healing efficiency.

Reduction of polyketone membranes prepared by thermally induced phase separation with solvent co-extrusion for enhanced fouling resistance

This study utilized solvent co-extrusion technology and NaBH4 reduction to fabricate polyketone (PK) hollow fiber membranes with high water permeance and fouling resistance. Variations in reduction reaction time were explored to assess their impact on chemical composition, morphology, and properties. The results showed that the reduction reaction leads to the conversion of carbonyl groups on the membrane surface to hydroxyl groups, and with prolonged reaction time, the amount of hydroxyl groups on the membrane surface increases to a certain extent. The change in membrane chemical composition enhanced the hydrophilicity, while leaving the membrane morphology, mechanical properties, and separation performance largely unaffected. Static adsorption tests with bovine serum albumin (BSA) and E. coli exhibited distinct fouling behavior. While pristine PK membranes displayed significant BSA adsorption, PK reduction significantly reduced it. Both pristine and reduced PK membranes showed minimal E. coli attachment, likely due to weak interactions. Dynamic filtration tests demonstrated excellent flux recovery for reduced PK membranes, especially after 10 min of reduction, indicating superior fouling resistance with high flux recovery and low irreversible fouling, regardless of foulant type. These findings highlight a straightforward and efficient approach for producing high-performance membranes with exceptional fouling resistance suitable for practical applications.

Design of PVDF hollow fiber membranes with stable crystalline and porous structure by solvent‐free method

AbstractOne of the critical principles of green chemistry and environmental sustainability is to avoid using harmful solvents in chemical processes. In this study, a novel solvent‐free method was employed to prepare poly (vinylidene fluoride) (PVDF) hollow fiber composite membranes with stable crystalline and porous structures. Utilizing the cold‐hot stretching method, the crystalline structure and orientation of PVDF were effectively redesigned, resulting in improved mechanical and penetration properties of the membrane. Additionally, an investigation into the internal crystalline structure of the PVDF hollow fiber membrane was conducted, focusing on crystalline changes induced by ion‐dipole interactions. Results indicated that the addition of neutral ion‐dipole functional particles (N‐P) promoted the conversion of α crystalline to β crystalline, leading to stable β crystalline and controllable pore sizes in the prepared PVDF hollow fiber membrane. Furthermore, the internal crystalline structure significantly contributed to enhancing the membrane's mechanical properties and penetration performance. Notably, a PVDF hollow fiber with high β crystalline content was achieved through 150% cold‐hot stretching and the addition of 20. wt% N‐P further enhanced the β‐crystalline content in the membrane. This study presents a promising approach for reducing solvent consumption and minimizing environmental impact in the field of environment‐friendly membrane fabrication.

Dual-stimuli-responsive poly(vinyl alcohol) nanofibers for localized cancer treatment: Magnetic hyperthermia and drug release studies

Smart materials are a promising option for a more personalized cancer treatment approach. In particular, materials that can respond to an external stimulus may be manipulated to provide a tailored response when and where it is needed. This work confined thermoresponsive poly (N-isopropyl acrylamide) microgels and superparamagnetic iron oxide nanoparticles into poly (vinyl alcohol) nanofibrous membranes. Physical and chemical crosslinking methods were tested to obtain membranes stable in physiological environments for long-term applications, and their effect on the membranes' morphology, swelling, and mechanical properties was evaluated. The results demonstrated that thermal crosslinking for 10 min is enough to obtain a robust membrane for biomedical applications that retain their components' magnetic and thermal responses. The swelling degree decreases with the increase of crosslinking time and is even smaller for chemically crosslinked membranes. Similarly, a high crosslinking degree is associated with more brittle membranes than ductile membranes with thermal crosslinking. Drug delivery assays using doxorubicin as a model drug demonstrated that only membranes with a smaller crosslinking degree are suitable for drug delivery purposes, with about 10 % of doxorubicin released for 15 days. Additionally, magnetic hyperthermia assays showed that composite membranes can increase the surrounding temperature by 10 °C in only 10 min of applying an alternating magnetic field. This work demonstrates the potential of combining stimuli-responsive materials using a simple, low-cost, and easily scalable technique (electrospinning) to produce smart materials for biomedical applications.

Synergistic contribution of sulfonated poly(ether sulfone) and iminodiacetic acid functionalized-graphene oxide nanosheets towards enhancing cationic dye wastewater purification using nanocomposite membranes

Water purification and wastewater treatment can be achieved using membrane technologies. However, conventional poly(ether sulfone) (PES) membranes suffer from hydrophobicity, fouling issues, and insufficient dye removal. In this study, hydrophilic sulfonated PES (sPES) and iminodiacetic acid-functionalized graphene oxide (IDA-GO) nanosheets were incorporated into the PES membranes to enhance cationic dye removal efficiency. PES/sPES membranes containing 0.05–0.2 wt% IDA-GO nanosheets were fabricated via phase inversion. PES/sPES@IDA-GO membrane and IDA-GO nanosheets were fully characterized using various analytical techniques. With a negative surface charge, the PES/sPES@IDA-GO membrane is a good candidate to remove cationic days. Compared with pristine PES membranes, hydrophilic nanosheets improve membrane porosity, hydrophilicity, and mechanical properties. Further altering the membrane structure by incorporating IDA-GO nanosheets into the PES/sPES-based casting solution increased the porosity and mean pore radius. Using PES/sPES@IDA-GO membrane containing IDA-GO nanosheets as low as 0.1 wt%, values of 99.9 % 19.4 L/m2.h were achieved for dye rejection and pure water flux, respectively. Tuning membrane properties using sPES and IDA-GO nanosheets enabled exceptional cationic dye removal. This offers a facile approach to engineering high-performance PES membranes for effective wastewater purification and environmental remediation applications.

Preparation and properties of modified POD membranes by polycarboxylic acids copolymerization

A series of X-POD polymers were prepared by condensation reaction of terephthalic dihydrazide and four different polycarboxylic acids in polyphosphoric acid (PPA) as solvent, and the corresponding membranes were formed by phase inversion method. The modified X-POD polymer structures have changed from linear structure to multidimensional network structure, which has great influence on the quality and performance of the membranes. The membrane structures were characterized by FTIR, and the thermal stability of the samples was determined by Thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). The ultraviolet transmittance and fluorescence properties of membranes were tested by ultraviolet spectrophotometer. The crystallinity and orientation of the samples were observed by X-ray diffraction (XRD). The surface and cross-sectional morphology of the membranes were evaluated by scanning electron microscope (SEM). Additionally, the oxidation and water absorption properties of the membranes were collected, and the mechanical properties of the membranes were tested. Overall, X-POD membranes show good mechanical properties, chemical inertness and thermal stability. The quality and mechanical properties of X-POD membranes demonstrated varying degrees of improvement. Notably, the mechanical properties of II-POD and III-POD membranes were enhanced by 244.52% and 203.66%, respectively. X-POD membranes exhibit high strength and excellent toughness, rendering them a highly promising material for membrane applications in the market.

Silane-crosslinked polybenzimidazole with different hydroxyl content for high-temperature proton exchange membrane

High temperature proton exchange membrane fuel cells (HT-PEMFCs) can operate over 100 °C without humidification, which avoids the catalyst poisoning and enhances the efficiency of the power conversion. However, the classic phosphoric acid (PA) doped polybenzimidazole (PBI) still remains the challenge in the trade-off between mechanical strength and proton conductivity. The γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH560), as a crosslinking agent, is widely used to improve the mechanical properties of membranes. Although it can enhance the mechanical strength of PBI membranes, it sacrifices the hydrogen of imidazole groups, resulting in a decrease in proton conductivity. In this present work, silane-crosslinked PBI proton exchange membranes (PEMs) were synthesized by the reaction between the pyridine-bridged PBI containing different hydroxyl (-OH) content with KH560. Through comprehensive structural characterization of the polymer and model compound, it has been determined that this crosslinking method does not compromise the N–H acidic sites on the imidazole ring. The crosslinking agent KH560 provides additional hydroxyl groups to PBI and participates in the construction of hydrogen bonding networks after the ring-opening reaction. It was found that the addition of pyridine and hydroxyl groups could promote the phosphoric acid uptake, and the appropriate degree of silane crosslinking could maintain the PBI membranes with reasonable mechanical properties. Proton conductivity and HT-PEMFCs performance of the obtained crosslinked films were further enhanced with the dimensional stability, thermal stability and mechanical properties. Among them, CPyOPBI–OH–20 presented the best overall performance, exhibiting the highest proton conductivity of 0.095 S cm−1 and the maximum power density of 767 mW cm−2 at 180 °C under the anhydrous condition, which was 4.2 times that of OPBI (182 mW cm−2).

Inferring biophysical properties of membranes during endocytosis using machine learning.

Endocytosis is a fundamental cellular process in eukaryotic cells that facilitates the transport of molecules into the cell. With the help of fluorescence microscopy and electron tomography, researchers have accumulated extensive geometric data of membrane shapes during endocytosis. These data contain rich information about the mechanical properties of membranes, which are hard to access via experiments due to the small dimensions of the endocytic patch. In this study, we propose an approach that combines machine learning with the Helfrich theory of membranes to infer the mechanical properties of membranes during endocytosis from a dataset of membrane shapes extracted from electron tomography. Our results demonstrate that machine learning can output solutions that both match the experimental profile and satisfy the membrane shape equations derived from Helfrich theory. The learning results show that during the early stage of endocytosis, the inferred membrane tension is negative, indicating the presence of strong compressive forces at the boundary of the endocytic invagination. Our method presents a generic framework for extracting membrane information from super-resolution imaging.

Synthesis and Structural Characterization of Four Different Concentrations of Ant Nest (Myrmecodia pendens) Collagen Membranes with Potential for Medical Applications.

The purpose of this study was to synthesize and structurally characterize four ant nest membranes in four different concentrations and determine the best concentration that could potentially be used as an alternative material for the production of new collagen barrier membranes. Membranes were created by mixing ant nest extracts at various concentrations of 0.5%, 1%, 1.5%, and 2%, as well as collagen, chitosan, and Polyvinyl Alcohol (PVA) using a film casting. A Universal Testing Machine (UTM) was used to evaluate mechanical properties including elastic modulus, tensile strength, maximum elongation, elongation at break, and maximum force. Water absorption was performed, FTIR was used for functional group identification, and morphology was examined using SEM. Additionally, EDS was used to identify the composition and distribution of elements in membranes. Statistical analysis was conducted using ANOVA (analysis of variance) and post hoc testing with a significance level of p <0.01 for quantitative data. The results showed that the mechanical properties produced the following mean (standard deviation): elastic modulus 0.87 Mpa (0.11), tensile strength 16.32 N/mm2 (2.46), maximum elongation 4.96% (1.72), elongation at break 5.23% (1.87), and maximum force 22.50 N (5.06). The average water absorption capacity of all four membranes had a p-value <0.01. FTIR spectrum showed various peaks corresponding to functional groups, while SEM results indicated a homogeneous mixture. EDS analysis confirmed that the addition of ant plant extract at 0.5%, 1%, and 1.5% resulted in the presence of elements C, O, and Ca. Meanwhile, membranes prepared with 2% concentration had a different composition, namely C, O, Ca, and Na. Increasing the concentration of ant nest affects the values of the membrane's mechanical properties parameters, including the elastic modulus (0.87 Mpa), tensile strength (16.32 N/mm2), maximum elongation (4.96%), elongation at break (5.23%), and maximum force (22.50 N). The average membrane absorption of water (p value <0.01) was also affected. SEM images showed homogeneous mixing, and membrane EDS results consisted of C, O, and Ca composition. However, there was no effect on FTIR functional groups. The anthill membrane with a 1% concentration has the potential to serve as an alternative membrane in guided tissue regeneration.

Recent advances in the interfacial engineering of MOF-based mixed matrix membranes for gas separation.

The membrane process stands as a promising and transformative technology for efficient gas separation due to its high energy efficiency, operational simplicity, low environmental impact, and easy up-and-down scaling. Metal-organic framework (MOF)-polymer mixed matrix membranes (MMMs) combine MOFs' superior gas-separation performance with polymers' processing versatility, offering the opportunity to address the limitations of pure polymer or inorganic membranes for large-scale integration. However, the incompatibility between the rigid MOFs and flexible polymer chains poses a challenge in MOF MMM fabrication, which can cause issues such as MOF agglomeration, sedimentation, and interfacial defects, substantially weakening membrane separation efficiency and mechanical properties, particularly gas separation. This review focuses on engineering MMMs' interfaces, detailing recent strategies for reducing interfacial defects, improving MOF dispersion, and enhancing MOF loading. Advanced characterisation techniques for understanding membrane properties, specifically the MOF-polymer interface, are outlined. Lastly, it explores the remaining challenges in MMM research and outlines potential future research directions.

Hydrodynamic interactions and membrane damage for a pair of microcapsules in shear flow: Effect of membrane mechanical properties

We model the hydrodynamic interaction of two equal size capsules in simple shear flow. The capsules may have different mechanical membrane properties. The results are analyzed in terms of a macro scale model of capsule membrane damage. We show how the interaction between two capsules with a membrane rigidity mismatch may lead to damage of the more deformable capsule even when the base flow strength is below the damage threshold of both capsules. We provide charts of the peak deformation energy density in the two membranes as a function of the flow strength and the ratio of the elastic rigidity of the two capsules. Given a damage criterion, those charts can be used to determine when flow-induced damage will occur in a suspension of capsules with a distribution of mechanical properties.

A greener route to prepare PEBAX®1074 membranes for gas separation processes

The solvent used in membrane fabrication is crucial for a potential industrial application, with a direct effect on its safety, environmental and economic impact. Thus, in the last years, the search for greener and safer solvents became of utmost importance aiming for a sustainable fabrication of highly performing membranes, since that also affects the final membrane morphology. Typically, solvent evaporation-based methods are used for the preparation of membranes for gas separation processes, such as dip-coating and spray coating methods. The advantage of this approach relies on the possibility of using greener non-toxic solvents, such as water and ethanol. However, an alternative route might involve the use of phase inversion methods. In this procedure, the selection of the solvent will play an even more important role, with an impact on the gas separation membrane properties. Small defects or structural changes will decisively alter the final membrane performance.In this work, it is presented for the first time the alternative use of a non-toxic and eco-friendly solvent, Rhodiasolv®Polarclean, for the preparation of CO2-selective PEBAX®-based membranes using a hybrid phase inversion method. This preliminary study evaluates the relationship between the fabrication protocol, with the resulting structural, thermal, and mechanical membrane properties for self-standing membranes. The gas separation performance was tested for different gases: H2, N2, O2, CO2 and CH4. This analysis also includes a comparison with the commonly used, although strongly restricted and hazardous, solvent N-Methyl-2-Pyrrolidone (NMP).

Cellulose nanofibers based composite membrane with high solar radiation and heat conduction for agricultural thermal dissipation application

Thermal dissipation materials that can emit thermal radiation and enhance thermal conductivity are critical for agricultural thermal management and the establishment of an energy efficient society. Here, cellulose nanofibers based composite membranes are prepared by extraction, homogenization, alkali treatment, and steam modification using rice straw as raw materials for agricultural thermal management. The composite membranes not only achieve a radiative cooling effect with high solar emissivity (0.89) for outdoor thermal management but also enables a synergetic effect with high thermal conductivity (2.103 W·m−1·K−1) to reduce the internal temperature of agricultural films, which is 7.2 °C cooler than mulch films. The alkali treatment process enables the formation of hydrogen bonds between boron nitride and cellulose nanofibers, thereby significantly enhancing the composite membrane's mechanical properties. The composite membranes exhibited excellent mechanical strength due to the new hydrogen bonds between boron nitride and cellulose nanofibers. Therefore, this work provides new ideas for exploring the comprehensive utilization of agricultural waste and the working mechanism for the preparation of agricultural waste-based materials, as well as a low-carbon development path of “agriculture-environment-energy”.

Functionalized graphite carbon nitride nanofluid membranes for enhanced osmotic energy harvesting

Reverse electrodialysis is a promising technology that using ion exchange membrane to obtain electrical energy directly between seawater and river water. Current attempts that based on the ion exchange membrane are limited due to the channel size and low charge density. Graphitic carbon nitride (g-C3N4, GCN) is a type of graphite-layered polymer that combined with inherent nanopore structure and adjustable surface charge, which provides a shortcut for the preparation of highly selective ion exchange membrane. However, carbon nitride membranes still exhibit low power density. Herein, g-C3N4 was successfully functionalized with three different negatively charged molecules (carboxylation, polyacrylic acid (PAA) and poly (sodium 4-styrenesulfonare) (PSS)), which benefited from its rich nitrogen-containing groups. These functionalized g-C3N4 were combined with anodized aluminum oxide (AAO) membrane to form heterochannel membranes, which can transport counter-ions and harvest osmotic energy. The results showed that the surface charge density of functionalized g-C3N4 was obviously improved, which enhanced the output power density. Among them, the heterochannel membrane functionalized with PSS (PSS-CN/AAO) had the highest output power density of 31 mW/m2 (effective area 4.9 mm2), which was 3.1 times higher than that of the unfunctionalized heterochannel membrane (GCN/AAO, 9 mW/m2). In this base, two-dimensional PSS-CN/ANF membranes were designed by compositing PSS-functionalized g-C3N4 (PSS-CN) nanosheets with aramid nanofiber (ANF), which can maintain high output power density (50 mW/m2) and further improve the mechanical property of membrane, providing a guarantee for the long-term stable use of nanofluid membrane.

Preparation and Self-Cleaning Performance of High-Strength Double-Layer PVDF-PVC-Nano-Graphite/PVDF-PVC Super-Hydrophobic Composite Membrane

The double-layer PVDF-PVC (D-PP/PP) super-hydrophobic composite membrane was prepared by the coating immersion phase separation method to enhance the mechanical properties of the composite membrane. The D-PP/PP super-hydrophobic membrane was prepared using the casting solution concentration of 12 wt% PVDF-PVC composite membrane as basement and 4% casting of PVDF-PVC coating. The contact angle of the D-PP/PP membrane was 150.4 ± 0.3°, and the scanning electron microscope showed that the surface of the D-PP/PP membrane was covered by a cross-linked micro–nano microsphere. The mechanical properties showed that the maximum tensile force of the D-PP/PP composite membrane was 2.34 N, which was 19.4% higher than that of PVDF-PVC (1.96 N). Nano-graphite was added to the coating layer in the experiment. The prepared double-layer PVDF-PVC-nano-graphite/PVDF-PVC (D-PPG/PP) composite membrane reached 153.7 ± 0.5°, the contact angle increasing by 3.3°. The SEM comparison showed that the D-PPG/PP composite membrane had a more obvious micro–nano level microsphere layer. The mechanical properties are also superior. By preparing the D-PP/PP membrane, the mechanical properties of the membrane were improved, and the super-hydrophobic property of the coating was also obtained. At the same time, it was found that adding nano-graphite to the coating layer can better improve the hydrophobic, mechanical, and self-cleaning properties of the D-PP/PP composite membrane.

The underlying mechanical properties of membranes tune their ability to fuse

Membrane fusion is a ubiquitous process associated with a multitude of biological events. Although it has long been appreciated that membrane mechanics plays an important role in membrane fusion, the molecular interplay between mechanics and fusion has remained elusive. For example, although different lipids modulate membrane mechanics differently, depending on their composition, molar ratio, and complex interactions, differing lipid compositions may lead to similar mechanical properties. This raises the question of whether (i) the specific lipid composition or (ii) the average mesoscale mechanics of membranes acts as the determining factor for cellular function. Furthermore, little is known about the potential consequences of fusion on membrane disruption. Here, we use a combination of confocal microscopy, time-resolved imaging, and electroporation to shed light onto the underlying mechanical properties of membranes that regulate membrane fusion. Fusion efficiency follows a nearly universal behavior that depends on membrane fluidity parameters, such as membrane viscosity and bending rigidity, rather than on specific lipid composition. This helps explaining why the charged and fluid membranes of the inner leaflet of the plasma membrane are more fusogenic than their outer counterparts. Importantly, we show that physiological levels of cholesterol, a key component of biological membranes, has a mild effect on fusion but significantly enhances membrane mechanical stability against pore formation, suggesting that its high cellular levels buffer the membrane against disruption. The ability of membranes to efficiently fuse while preserving their integrity may have given evolutionary advantages to cells by enabling their function while preserving membrane stability.

Fabrication of photocatalytic PAN nanofiber membrane loading with TiO2@RGO by electro-spinning & electro-spraying

The new fibrous photocatalytic nanofiber membrane with both good photodegradation performance and mechanical property was developed. Here, TiO2@RGO (TR) which could disperse in PAN solution stably was prepared by solvothermal method with the help of acetic acid. Then the new photocatalytic PAN nanofiber membrane SS7.5-2.3 TR(A) was fabricated for the first time by electro-spinning & electro-spraying, where TR ruled as photocatalysts. Benefited from its novel triple structure, SS7.5-2.3 TR(A) had the best toughness when compared with S-0 (electro-spun dual-network structural membrane) and SS7.5 (control membrane without TR in electro-spraying solution). Moreover, the morphology and mechanical property of membrane was similar to that of original SS7.5-2.3 TR when it was used to photodegrade methyl orange solution five times later. Meanwhile, SS7.5-2.3 TR also had significant photocatalytic performance when applied to the degradation of other three dyes (rhodamine B, methylene blue and oil red) and silk dyeing wastewater, which indicated its potential in dyeing wastewater treatment.