Membrane Surface Energy Research Articles

Wetting-and scaling-resistant superhydrophobic hollow fiber membrane with hierarchical surface structure for membrane distillation

In this study, we address the challenge of wetting and scaling in membrane distillation (MD) by developing a robust superhydrophobic poly(vinylidene fluoride) (PVDF) hollow fiber membrane. To achieve this, we utilized co-extrusion technology and subsequent fluorination treatment to create micro-nanoscale surfaces. The fabrication process involved extruding a SiO2 suspension onto the outermost layer of a triple-orifice spinneret to create a hierarchical structure, followed by 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FAS) modification to lower the membrane surface energy. This resulted in a highly water-repellant membrane, as evidenced by contact angle measurements of 153°, 147°, and 141° for water, sodium dodecyl sulfate (SDS) solution (0.4 mM), and saline SDS solution (0.4 Mm SDS and 35 wt% NaCl), respectively, indicating increased resistance to liquid penetration. Through direct contact membrane distillation (DCMD) experiments, we demonstrated that the PVDF/FAS membrane exhibited excellent wetting resistance to seawater (3.5 wt% of NaCl) with SDS at varying concentrations. Furthermore, the membrane effectively hindered the CaSO4 scaling by reducing both heterogeneous nucleation and the tendency of bulk crystal deposition on the membrane outer surface. Overall, the developed approach for fabrication of superhydrophobic PVDF hollow fiber membrane presents a promising solution for facile and scalable manufacturing of anti-wetting and anti-scaling MD membranes. This advancement has significant implications for enhancing the practical application of MD technology.

Creating Nature-Inspired Surface Roughness and Modifying Surface Chemistry of PVDF Electrospun Fibers Using Low-Pressure Plasma towards Omniphobic Membrane for Long-term Distillation

Today, water scarcity as one of the world's most pressing challenges, has caused many concerns. Seawater desalination based on membrane distillation (MD) has been introduced as an effective solution to deal with this problem. The surface of membranes used in MD is required to be modified to guarantee long-term performance via creating resistance against membrane wetting by low surface tension feeds. In this regard, beetle skin-inspired roughness was created on the surface of poly(vinylidene fluoride) (PVDF) electrospun fibers using low-pressure plasma technique. Synergistically, 1H, 1H, 2H, 2H-perfluorooctyl acrylate (PFOA) was polymerized on the fiber surface to modify its chemistry. In other words, using the plasma polymerization technique, the membrane surface energy was reduced thanks to (1) the increase in membrane surface roughness and (2) the change in the membrane surface chemistry, as confirmed by field-emission scanning electron microscope (FESEM) imaging, X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. These changes led to an omniphobic membrane repelling water, engine oil and isopropanol with contact angles of 150°, 135°, and 119°, respectively. The long-term performance of the developed omniphobic membrane was demonstrated by conducting air gap membrane distillation (AGMD) for a duration as long as 600 min using a feed solution containing 3.5 wt% NaCl and 0.6 mM sodium dodecyl sulfate (SDS), which is ten times better than the performance of pristine membrane (60 min). Overall, the surface modification technique considered in this work yields an omniphobic membrane with stable long-term performance without compromising the membrane flux and salt rejection.

A hydrophobic-hydrophilic MXene/PVDF composite hollow fiber membrane with enhanced antifouling properties for seawater desalination

Hollow fiber membrane-based humidification-dehumidification desalination of seawater is a low-carbon freshwater-harvesting technology that can be powered by low-grade solar energy. Polyvinylidene fluoride (PVDF) can be easily fabricated into membranes and is considered the most promising material for industrial seawater desalination. However, membrane fouling and wetting have always been major obstacles with this technology. In this study, a hydrophobic-hydrophilic MXene/PVDF composite hollow fiber membrane (PVDF-MP) with remarkable antiwetting and antifouling properties was successfully prepared using a chemical grafting method. The interfacial dehydration reaction between the hydrophilic substrate layer (PVDF-OH) and the hydrophobic skin layer (MXene-P [MP]) was verified by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy, and a detailed reaction mechanism was provided. The hydrophilic substrate layer decreased moisture transfer resistance, while the hydrophobic skin layer reduced the membrane surface energy and increased the surface roughness. This resulted in a contact angle of 156.2°, which was measured using a new method that accounted for the curvature of the membrane. The superhydrophobic surface possessed a strong repulsive force toward water, and the air gap between the water and membrane impeded pollutant deposition on the inner surface of the membrane. Moreover, the rough surface created high entry pressure and prevented water from entering the membrane pores. Thus, the permeate flux of the PVDF-MP membrane persisted over 120 h during desalination tests, surpassing the performance of traditional materials. • A hydrophobic-hydrophilic MXene/PVDF composite hollow fiber membrane was prepared. • The PVDF hollow fiber membrane inner surface was superhydrophobically modified. • The interfacial force between the modified layer and substrate was enhanced. • A measuring method for the contact angle of hollow fiber membranes was proposed. • The composite membrane exhibited excellent anti-fouling and anti-wetting ability.

Functionalization of reverse osmosis membrane with titania nanotube and polyacrylic acid for enhanced antiscaling properties

Membrane surface scaling is a major challenge in reverse osmosis (RO) desalination process that could irreversibly deteriorate the membrane filtration efficiency. In this study, a hydrophilic coating layer was introduced onto the polyamide (PA) layer of self-developed thin film nanocomposite (TFN) membrane via plasma enhanced chemical vapour deposition (PECVD) technique to increase the membrane surface energy barrier and hydrophilicity towards silica heterogeneous nucleation. The results revealed that the acrylic acid-coated TFN membrane (AA-TFN) exhibited excellent resistance against silica scaling after subjected to saturated silica concentration (168 ppm at pH 6.7), with much higher flux recovery rate (FRR) (88%) compared to the uncoated TFN (75.5%) and conventional thin film composite (TFC) (72%) membranes. This is attributed to its enhanced surface hydrophilicity (contact angle of 26°) and better surface charge (zeta potential of −47 mV at pH 6.7) upon the hydrophilic coating layer deposition which retards the scale deposition. The membrane scaling can be further reduced by increasing the feed pH and at the optimized condition (pH 10), the FRR of AA-TFN membrane could reach up to 98.3%, owing to the increased silica solubility at alkaline condition which minimizes the silica aggregation formation on the membrane surface. Our work demonstrated that surface modification of composite membrane using suitable materials and proper feed pH adjustment could offer a great promise in mitigating the scaling for desalination applications. The findings also provide fundamental insights on the importance of membrane surface properties during silica scaling formation.

Extraordinary Superhydrophobic Polycaprolactone-Based Composite Membrane with an Alternated Micro-Nano Hierarchical Structure as an Eco-friendly Oil/Water Separator.

Extraordinary superhydrophobic polycaprolactone (PCL) composite membranes with an alternated hierarchical micro-nano structure were designed by addition of SiO2 aerogel. The highest water contact angle (WCA) of 166.8 ± 1.5° was obtained when SiO2 aerogel content was 0.5% (PCL/SiO2-a0.5) in the PCL composite membrane, which was higher than other reported polymer-based membranes. SiO2 aerogel lowered PCL composite membrane's surface energy. The triple curvature structure composed of microspheres, nanospheres, and nanofibers produced on PCL/SiO2-a0.5 membranes endowed the excellent roughness of the surface. Also, the inner structure of the PCL/SiO2-a0.5 composite membrane composed of micro-nano spheres, nanofibers, and microfibers increased the porosity of the separation membrane, which would provide more adsorption space. The PCL/SiO2-a0.5 composite membrane as a separator for surfactant-stabilized emulsions of water-in-oil showed ultrahigh separation flux and efficiency. Meanwhile, the PCL/SiO2-a0.5 composite membrane had an outstanding chemical resistance, self-cleaning ability, and good reusability. The composite membranes reported in this work as eco-friendly separation materials possessed all these characters in oil/water separation. This research proposed a very simple method to design eco-friendly high-efficiency separators through the construction of the alternated micro-nano hierarchical structure.

Impact of sodium hypochlorite on rejection of non-steroidal anti-inflammatory drugs by biomimetic forward osmosis membranes

Biomimetic forward osmosis membranes with a polyamide-based active layer containing polymersomes incorporating aquaporins were exposed to various free chlorine doses (free chlorine concentration x exposure time) and pH. Membrane chlorination was found to decrease the apolar/polar balance of the membrane surface energy and to increase its negative surface charge density. A substantial modification of the hydrogen-bond network in the membrane active layer was also highlighted. The separation performance of biomimetic membranes was also impacted by chlorine-induced chemical ageing. For the lowest free chlorine doses (100 ppm h), the reverse salt flux was found to increase with respect to the pristine membrane while the water flux dropped by 10–20%. For higher free chlorine doses (1000 and 10 000 ppm h), both the reverse salt flux and the water flux were found higher than for the pristine membrane. These behaviors were explained by the combination of several mechanisms with possible antagonist effects, namely a reduced internal concentration polarization due to ageing of the membrane support material, and modifications of the hydrogen-bond network and surface charge density of the membrane active layer. Although the degradation caused by sodium hypochlorite increased the draw-solute loss per unit of water passed, the biomimetic membranes maintained their rejection ability towards naproxen and diclofenac as rejections higher than 95.9% were measured irrespective of the ageing conditions.

Correlating the membrane surface energy to the organic fouling and wetting of membrane distillation at elevated temperature

Membrane fouling is an inevitable process but could be mitigated by understanding its fouling mechanism. In this work, organic fouling phenomena of direct contact membrane distillation (DCMD) on membrane with different surface properties were examined under high salinity and elevated temperature conditions. Membranes with different surface energies and pore structures showed different fouling phenomenon by the hydrophilic/amphiphilic polymer. Surface energy studies showed that molecular interaction between the organic solutes and Polytetrafluoroethylene (PTFE) membrane were strong enough to form the segregated or films like structure on the membrane. On the other hand, the weaker interactions between the Polyvinylidene fluoride (PVDF) membrane induced aggregated/precipitated form of foulants. The flux declination trend is very much depending on the characteristic of the foulants. The aggregated foulants could easily precipitate on the membrane surface to produce loose fouling layer that reduced the flux. However, the smaller precipitate could block the pores and gave significant flux declination. The effort to make the surface become more hydrophilic could reduce the fouling propensity of bovine serum albumin, however the hydrophilic PVDF layer was susceptible to higher wetting potential at elevated temperature. Increasing the surface hydrophobicity could alleviate the molecular interactions but its potential to interact via hydrophobic interactions could be an unwanted phenomenon. Therefore, studying the surface energy as well as pore structure of membrane is crucial to understand the organic fouling behaviour of DCMD at elevated temperature.

Superhydrophobic-omniphobic membrane with anti-deformable pores for membrane distillation with excellent wetting resistance

Wetting induced by salt-scaling and surfactants is the Achilles heel of membrane distillation, especially for concentration of high salinity wastewater. Herein, we rationally developed a membrane with robust wetting resistance by integrating superhydrophobic-omniphobic surface and anti-deformable pores into one system. The membrane was first developed by electrospinning, which was then modified with surface roughness, and followed by coating of polydimethylsiloxane to weld the intersecting fibers and fluoroalkylsilane to lower the membrane surface energy. The product exhibits excellent wetting resistance when concentrating the high salinity NaCl solution from 20 to 38 wt% (saturation condition), the simulated reverse osmosis concentrated water, the gypsum and the low-surface-tension high salinity wastewater. Moreover, the mechanism of membrane wetting resistance was also systematically discussed based on the experiment and computer simulation. It reveals that the superhydrophobic-omniphobic surface could stabilize the surface-bound air layer chemically, thus reducing the contact of crystals and surfactant with the membrane surface. Simultaneously, the anti-deformable pore also helps it overcome the asymmetrical hydraulic disturbance on enlarging membrane pore size, thus stabilizes the surface-bound air layer structurally. The presented development will provide a platform to understand and achieve wetting and scaling inhibition MD membrane for high salinity wastewater treatment.

Desolvation-Triggered Versatile Transfer-Printing of Pure BN Films with Thermal-Optical Dual Functionality.

Although hexagonal boron nitride (BN) nanostructures have recently received significant attention due to their unique physical and chemical properties, their applications have been limited by a lack of processability and poor film quality. In this study, a versatile method to transfer-print high-quality BN films composed of densely stacked BN nanosheets based on a desolvation-induced adhesion switching (DIAS) mechanism is developed. It is shown that edge functionalization of BN sheets and rational selection of membrane surface energy combined with systematic control of solvation and desolvation status enable extensive tunability of interfacial interactions at BN-BN, BN-membrane, and BN-substrate boundaries. Therefore, without incorporating any additives in the BN film and applying any surface treatment on target substrates, DIAS achieves a near 100% transfer yield of pure BN films on diverse substrates, including substrates containing significant surface irregularities. The printed BNs demonstrate high optical transparency (>90%) and excellent thermal conductivity (>167 W m-1 K-1) for few-micrometer-thick films due to their dense and well-ordered microstructures. In addition to outstanding heat dissipation capability, substantial optical enhancement effects are confirmed for light-emitting, photoluminescent, and photovoltaic devices, demonstrating their remarkable promise for next-generation optoelectronic device platforms.

Beading of injured axons driven by tension- and adhesion-regulated membrane shape instability

The formation of multiple beads along an injured axon will lead to blockage of axonal transport and eventually neuron death, and this has been widely recognized as a hallmark of nervous system degeneration. Nevertheless, the underlying mechanisms remain poorly understood. Here, we report a combined experimental and theoretical study to reveal key factors governing axon beading. Specifically, by transecting well-developed axons with a sharp atomic force microscope probe, significant beading of the axons was triggered. We showed that adhesion was not required for beading to occur, although when present strong axon–substrate attachments seemed to set the locations for bead formation. In addition, the beading wavelength, representing the average distance between beads, was found to correlate with the size and cytoskeleton integrity of axon, with a thinner axon or a disrupted actin cytoskeleton both leading to a shorter beading wavelength. A model was also developed to explain these observations which suggest that axon beading originates from the shape instability of the membrane and is driven by the release of work done by axonal tension as well as the reduction of membrane surface energy. The beading wavelength predicted from this theory was in good agreement with our experiments under various conditions. By elucidating the essential physics behind axon beading, the current study could enhance our understanding of how axonal injury and neurodegeneration progress as well as provide insights for the development of possible treatment strategies.

Biomimetic superhydrophobic membrane for membrane distillation with robust wetting and fouling resistance

Membrane distillation (MD) is a promising membrane-based thermal process capable of desalinating highly saline water. However, its application is limited by fouling and wetting of commercial hydrophobic membranes. Inspired by the lotus leaf, we developed a biomimetic superhydrophobic polyvinylidene fluoride (PVDF) membrane for robust MD via self-assembly method. The hierarchical micro-nanoscale texture on the membrane surface was constructed by grafting the spherical polyvinylsilsesquioxane (PVSQ) nanoparticles onto micron-sized silica particles (SiPs). The membrane surface energy can be simultaneously lowered due to the hydrophobic groups including vinyls and methoxyls created from the condensation reaction of the vinyltrimethoxysilane (VTMOS). The resulting membrane showed a very high water contact angle (~160°) and a low water sliding angle (<15°), demonstrating the strong hydrophobicity that is expected for a lotus-leaf-like surface. Compared to the commercial PVDF membrane, the fabricated superhydrophobic membrane exhibited superior resistance against wetting by a surfactant (sodium dodecyl sulfate) and fouling by humic acid during MD experiments. Our results suggest that biomimetic superhydrophobic membranes can enhance the operational robustness of MD and facilitate the efficient use of MD for desalinating saline wastewaters in favor of beneficial water reuse and resource recovery.

Patterned superhydrophobic polyvinylidene fluoride (PVDF) membranes for membrane distillation: Enhanced flux with improved fouling and wetting resistance

The industrial implementation of membrane distillation (MD) is still limited due to major barriers such as membrane wetting and low permeate flux. In this study, we fabricated a two-layer patterned superhydrophobic polyvinylidene fluoride (PVDF) membrane by combining non-solvent induced, and vapor induced phase separation processes (NIPS and VIPS), and a subsequent surface fluorination to lower the membrane's surface energy. A simple spacer imprinting method induced changes in the formation mechanism and formed a uniform pattern at the membrane surface increasing the effective surface area and achieving 18% higher flux, compared to a commercial membrane. Moreover, the patterns introduced surface turbulence and favorable flow hydrodynamics that highly improved fouling mitigation when tested in MD with real sweater feed, where the flux was reduced by only 15.2% after 97 h of operation, compared to complete fouling and 100% flux reduction for the commercial membrane. The superhydrophobicity of the developed membrane, characterized by its high water contact angle of 154.5°, also achieved improved wetting resistance when low surface tension surfactant sodium dodecyl sulfate (SDS) was introduced to lower the surface tension of the feed seawater. Our findings indicate the ability of a patterned superhydrophobic membrane surfaces to produce high flux while at the same time enhance fouling and wetting durability, demonstrating their advantage for MD treatment of challenging feeds comprising both fouling and wetting contaminants.

Relating Organic Fouling in Membrane Distillation to Intermolecular Adhesion Forces and Interfacial Surface Energies

This study investigates the fouling mechanisms in membrane distillation, focusing on the impact of foulant type and membrane surface chemistry. Interaction forces between a surface-functionalized particle probe simulating a range of organic foulants and model surfaces, modified with different surface energy materials, were measured by atomic force microscopy. The measured interaction forces were compared to those calculated based on the experimentally determined surface energy components of the particle probe, model surface, and medium (i.e., water). Surfaces with low interfacial energy exhibited high attractive interaction forces with organic foulants, implying a higher fouling potential. In contrast, hydrophilic surfaces (i.e., surfaces with high interfacial energy) showed the lowest attractive forces with all types of foulants. We further performed fouling experiments with alginate, humic acid, and mineral oil in direct contact membrane distillation using polyvinylidene fluoride membranes modified with various materials to control membrane surface energy. The observed fouling behavior was compared to the interaction force data to better understand the underlying fouling mechanisms. A remarkable correlation was obtained between the evaluated interaction force data and the fouling behavior of the membranes with different surface energy. Membranes with low surface energy were fouled by hydrophobic, low surface tension foulants via "attractive" and subsequent "adsorptive" interaction mechanisms. Furthermore, such membranes have a higher fouling potential than membranes with high or ultralow surface energy.

Engineered Slippery Surface to Mitigate Gypsum Scaling in Membrane Distillation for Treatment of Hypersaline Industrial Wastewaters.

Membrane distillation (MD) is an emerging thermal desalination process, which can potentially treat high salinity industrial wastewaters, such as shale gas produced water and power plant blowdown. The performance of MD systems is hampered by inorganic scaling, particularly when treating hypersaline industrial wastewaters with high-scaling potential. In this study, we developed a scaling-resistant MD membrane with an engineered "slippery" surface for desalination of high-salinity industrial wastewaters at high water recovery. A polyvinylidene fluoride (PVDF) membrane was grafted with silica nanoparticles, followed by coating with fluoroalkylsilane to lower the membrane surface energy. Contact angle measurements revealed the "slippery" nature of the modified PVDF membrane. We evaluated the desalination performance of the surface-engineered PVDF membrane in direct contact membrane distillation using a synthetic wastewater with high gypsum scaling potential as well as a brine from a power plant blowdown. Results show that gypsum scaling is substantially delayed on the developed slippery surface. Compared to the pristine PVDF membrane, the modified PVDF membranes exhibited a stable MD performance with reduced scaling potential, demonstrating its potential to achieve high water recovery in treatment of high-salinity industrial wastewaters. We conclude with a discussion of the mechanism for gypsum scaling inhibition by the engineered slippery surface.

Relationship between Energy Characteristics of Surface of Polymeric Membranes and Their Transport Properties

Molecular theory of wetting was used to calculate the specific free surface energy of membranes based on amorphous polymers of varied chemical structure from experimental wetting angles obtained for test fluids. A relationship was found between the dispersion component of the surface energy of a membrane, its gas permeability, and free volume of the polymer. This makes it possible to employ the wetting method to prognosticate the transport properties of polymeric membranes. In wetting of membranes with aqueous solutions of alcohols, the concentration of an alcohol corresponding to the onset of its sorption into the membrane was determined. The correlation of the value obtained with the alcohol concentration that corresponds to the onset of sorption and is determined independently by the gravimetric method enables use of wetting angles for optimizing the conditions of experiments on nanofiltration and pervaporation.

Engineering the Re-Entrant Hierarchy and Surface Energy of PDMS-PVDF Membrane for Membrane Distillation Using a Facile and Benign Microsphere Coating.

To consolidate the position of membrane distillation (MD) as an emerging membrane technology that meets global water challenges, it is crucial to develop membranes with ideal material properties. This study reports a facile approach for a polyvinylidene fluoride (PVDF) membrane surface modification that is achieved through the coating of the surface with poly(dimethylsiloxane) (PDMS) polymeric microspheres to lower the membrane surface energy. The hierarchical surface of the microspheres was built without any assistance of a nano/microcomposite by combining the rapid evaporation of tetrahydrofuran (THF) and the phase separation from condensed water vapor. The fabricated membrane exhibited superhydrophobicity-a high contact angle of 156.9° and a low contact-angle hysteresis of 11.3°-and a high wetting resistance to seawater containing sodium dodecyl sulfate (SDS). Compared with the control PVDF-hexafluoropropylene (HFP) single-layer nanofiber membrane, the proposed fabricated membrane with the polymeric microsphere layer showed a smaller pore size and higher liquid entry pressure (LEP). When it was tested for the direct-contact MD (DCMD) in terms of the desalination of seawater (3.5% of NaCl) containing SDS of a progressively increased concentration, the fabricated membrane showed stable desalination and partial wetting for the 0.1 and 0.2 mM SDS, respectively.

Omniphobic Polyvinylidene Fluoride (PVDF) Membrane for Desalination of Shale Gas Produced Water by Membrane Distillation.

Microporous membranes fabricated from hydrophobic polymers such as polyvinylidene fluoride (PVDF) have been widely used for membrane distillation (MD). However, hydrophobic MD membranes are prone to wetting by low surface tension substances, thereby limiting their use in treating challenging industrial wastewaters, such as shale gas produced water. In this study, we present a facile and scalable approach for the fabrication of omniphobic polyvinylidene fluoride (PVDF) membranes that repel both water and oil. Positive surface charge was imparted to an alkaline-treated PVDF membrane by aminosilane functionalization, which enabled irreversible binding of negatively charged silica nanoparticles (SiNPs) to the membrane through electrostatic attraction. The membrane with grafted SiNPs was then coated with fluoroalkylsilane (perfluorodecyltrichlorosilane) to lower the membrane surface energy. Results from contact angle measurements with mineral oil and surfactant solution demonstrated that overlaying SiNPs with ultralow surface energy significantly enhanced the wetting resistance of the membrane against low surface tension liquids. We also evaluated desalination performance of the modified membrane in direct contact membrane distillation with a synthetic wastewater containing surfactant (sodium dodecyl sulfate) and mineral oil, as well as with shale gas produced water. The omniphobic membrane exhibited a stable MD performance, demonstrating its potential application for desalination of challenging industrial wastewaters containing diverse low surface tension contaminants.

Performance of chemically modified TiO2-poly (vinylidene fluoride) DCMD for nutrient isolation and its antifouling properties

The surface properties of TiO2-PVDF nanocomposite membranes were investigated by incorporating different chemically modified TiO2 nanoparticles into the poly (vinylidene fluoride) (PVDF) matrix. The nanocomposite membranes were prepared via dual coagulation bath diffusion and the induced phase inversion method. The membrane surface morphologies were investigated by using SEM and AFM and related to the membrane surface energy via contact angle goniometry. The results showed that the average membrane surface pore sizes were increased with the addition of TiO2 nanoparticles. Nonetheless, the contact angle measurements demonstrated that the hydrophobicity of nanocomposite membranes can be maintained even with the addition of hydrophilic TiO2. This observation could be rationalized as surface roughness enhancement. The experimental results demonstrated that the initial flux of acid treated TiO2 has both higher initial flux and high COD removal due to their induced surface roughness. The TiO2-PVDF membranes were found to possess the significant bactericidal effect on B. Subtilis compared to the neat membrane even without the presence of UV light.

Interfacial Energy and Glass Temperature of Polymers Confined to Nanoporous Alumina

We report on the effect of interfacial energy on the glass temperature, Tg, of several amorphous polymers with various glass temperatures and polymer/substrate interactions confined within self-ordered nanoporous alumina (AAO). The polymers studied include poly(phenylmethylsiloxane) (PMPS), poly(vinyl acetate) (PVAc), 1,4-polybutadiene (PB), oligostyrene (PS), and poly(dimethylsiloxane) (PDMS). The segmental dynamics and associated Tg’s are studied by means of dielectric spectroscopy. The interfacial energy for the polymer/substrate interface, γSL, is calculated with Young’s equation whereas the AAO membrane surface energy is obtained by measuring contact angles for several reference liquids. We find that interfacial energy plays a significant role in the segmental dynamics of polymers under confinement within AAO. There is a trend for a decreasing glass temperature relative to the bulk with increasing interfacial energy. PDMS exhibits the highest interfacial energy and the highest reduction in glass temp...

Promoted water transport across graphene oxide–poly(amide) thin film composite membranes and their antibacterial activity

Hybrid composite membranes have great potential for desalination applications since water transport can be favorably promoted by selective diffusion at the interface between matrix and reinforcement materials. In this paper, graphene oxide nano-sheets were successfully incorporated across 200nm thick poly(amide) films by interfacial polymerization to form novel thin-film composite membranes. The impact of the graphene oxide on the morphology, chemistry, and surface charge of the ultra-thin poly(amide) layer, and the ability to desalinate seawater was investigated. The graphene oxide nano-sheets were found to be well dispersed across the composite membranes, leading to a lower membrane surface energy and an enhanced hydrophilicity. The iso-electric point of the samples, key to surface charge repulsion during desalination, was found to be consistently shifted to higher pH values with an increasing graphene oxide content. Compared to a pristine poly(amide) membrane, the pure water flux across the composite membranes with 0.12wt.% of graphene oxide was also found to increase by up to 80% from 0.122 to 0.219L·μm·m−2·h−1·bar−1 without significantly affecting salt selectivity. Furthermore, the inhibitory effects of the composite membrane on microbial growth were evaluated and the novel composite membranes exhibited superior anti-microbial activity and may act as a potential anti-fouling membrane material.