Non-solvent Induced Phase Separation Method Research Articles

Development of three-dimensional piezoelectric polyvinylidene fluoride-graphene oxide scaffold by non-solvent induced phase separation method for nerve tissue engineering

In this work, non-solvent induced phase separation method was applied to develop polyvinylidene fluoride (PVDF)/graphene oxide (GO) scaffold for nerve tissue engineering. Furthermore, the effects of GO concentration (0, 0.5, 1, 3 and 5 wt%) on the electrical, mechanical, physical and biological properties of scaffolds were also evaluated. Results demonstrated that, incorporation of GO nanosheets in the PVDF matrix decreased water contact angle, while enhanced the hydrophilicity, water absorption and water flux of the scaffolds. Moreover, mechanical properties of the nanocomposite scaffolds improved in the presence of GO nanosheets. Significantly, increasing GO content up to 3 wt% enhanced tensile modulus and strength of PVDF scaffold from 8.1 ± 1.4 and 0.8 ± 0.2 MPa to 17.0 ± 3.7 and 1.4 ± 0.4 MPa, respectively. Incorporation of GO nanosheets into the PVDF scaffold simultaneously enhanced β phase fraction, piezoelectricity and electrical conductivity of all nanocomposite scaffolds. Furthermore, PVDF-GO scaffolds significantly promoted cell proliferation, compared to PVDF scaffold, depending on the GO content. Finally, PVDF-GO scaffold could easily be converted in to a nerve guidance conduit with 4 internal longitudinally aligned channels making it appropriate for the nerve regeneration applications.

Preparation of high-flux PSF/GO loose nanofiltration hollow fiber membranes with dense-loose structure for treating textile wastewater

In this work, we reported the fabrication of novel loose nanofiltration (NF) hollow fiber membranes with dense-loose structure by one-step non-solvent induced phase separation (NIPS) method without post treatment. We selected air and graphene oxide (GO) as bore fluid and additive, respectively. The effects of air and GO on the properties of the prepared membranes were investigated based on field emission scanning electron microscope (SEM) image, pore size distribution, differential scanning calorimetry (DSC), Raman spectra, X-ray photoelectron spectrometer (XPS), water contact angle, zeta potential, mechanical strength, permeability, and rejection. The prepared membranes presented a long-term stability with a high dye rejection of 99.9% for treating the simulated textile wastewater. Meanwhile, the flux was much higher than those of the other reported membranes. Therefore, our prepared membranes showed a great potential for treating textile wastewater.

Guanidyl-functionalized graphene/polysulfone mixed matrix ultrafiltration membrane with superior permselective, antifouling and antibacterial properties for water treatment

Mixed matrix membranes blended with graphene-based nanomaterials have great potential in water and wastewater treatment on account of their multiple functionalities. To solve the complicated biofouling problem and diversify the applications of membranes, novel synergistic antibacterial guanidyl-functionalized graphene/polysulfone (GFG/PSF) mixed matrix ultrafiltration membranes were prepared by a non-solvent induced phase separation method. The guanidyl-functionalized graphene nanosheets were achieved by a two-step grafting process consisting of amination and guanidination and exhibited high dispersibility in the casting solution, which showed good compatibility with the polymer matrix. Besides the advantages of partially reduced graphene oxide (GO) nanosheets in creating a stronger interaction with the bacterial cell membrane to destroy the bacteria, the induced bidendate binding between guanidyl groups and phosphate groups on the cell wall can make high sterilization rate even at low concentrations. Different techniques including XRD, FTIR, XPS, SEM, TEM, EDX, contact angle meter, filtration and antibacterial experiments were employed to characterize and investigate the performance of nanosheets and membranes. Compared with pure PSF membrane, the GFG/PSF mixed matrix membranes not only exhibited superior permeability and prominent antifouling property performance toward bovine serum albumin (BSA), but also displayed excellent antimicrobial activity and long-term duration toward Escherichia coli and Staphylococcus aureus.

Preparation of Porous Polymeric Membranes Based on a Pyridine Containing Aromatic Polyether Sulfone.

Polymeric membranes, based on a polysulfone-type aromatic polyether matrix, were successfully developed via the non-solvent induced phase separation (NIPS) method. The polyethersulfone type polymer poly[2-(4-(diphenylsulfonyl)-phenoxy)-6-(4-phenoxy) pyridine] (PDSPP) was used as the membrane matrix, and mixed with its sulfonated derivative (SPDSPP) and a polymeric porogen. The SPDPPP was added to impart hydrophilicity, while at the same time maintaining the interactions with the non-sulfonated aromatic polyether forming the membrane matrix. Different techniques were used for the membranes’ properties characterization. The results revealed that the use of the non-sulfonated and sulfonated polymers of the same polymeric backbone, at certain compositions, can lead to membranes with controllable porosity and hydrophilicity.

Effect of bimodal pores on sintering and residual stresses of YSZ membranes prepared by non-solvent induced phase separation method

Densification mismatch and residual stresses of tri-layered yttria-stabilized zirconia (YSZ) membranes prepared by a non-solvent induced phase separation (NIPS) method were investigated. The tri-layered membrane consisted of sponge-like structures and finger-like voids in macroscale. The densification of the two structures were characterized to elaborate their contribution to the densification mismatch, which led to residual stresses of hundreds of megapascal retained in the sintered membranes. The profile of residual stress suggested that it was related to the strain rate mismatch within the NIPS membranes, which was further quantified with an in-situ monitored camber evolution.

Preparation and dielectric properties of porous cyanoethyl cellulose membranes

Cyanoethyl cellulose (CEC) with a high degree of substitution of cyanoethyl group was synthesized by using the Michael addition reaction. Porous CEC membranes were successfully prepared by the non-solvent induced phase separation method. The parameters that influence the morphology and properties of the CEC membranes were investigated and discussed. Asymmetric membranes with higher porosity were obtained when water was used for the coagulation bath. On the other hand, dense symmetric CEC membranes with cellular or flat pores were obtained when ethanol or DMF/H2O was used for the coagulation bath. The porosity of the CEC membranes was reduced with increased polymer concentration in the CEC/DMF solutions. Moreover, the morphology of CEC membranes also depended on the molecular weight of CEC. In the case of using water as the coagulation bath, the morphology of the CEC membranes changed from an asymmetric structure with dense thin skin layer to a stick-like intertwined symmetric structure. When ethanol or DMF/H2O was used for the coagulation bath, the morphology of the resultant symmetric CEC membranes changed from cellular or flat pores to stick-like intertwined structure. The dielectric constant of the CEC membranes increased with a decrease in the porosity of CEC membranes.

Electrically responsive ultrafiltration polyaniline membrane to solve fouling under applied potential

Membrane fouling is indispensable in all membrane systems and remains one major problem to large scale application. In view of this, an in-situ method of fouling control is desperately needed to sustain membrane technologies. The objective of this study is to develop electrically conductive PANI membranes with stimuli-response properties and to solve fouling under applied potential. Electrically conductive polyaniline membranes were prepared by non-solvent induced phase separation method. Exfoliated graphite and DBSA were incorporated into membrane to form PANI membranes with different electrical conductivities. The results showed that the conductivity of Memb-PAMPSA was improved by two orders of magnitude by the incorporation of EG, and further enhanced by twenty times using a long chain acid DBSA as a secondary dopant. Compared to Memb-PAMPSA whose effective contact angle did not change between 0 and 30 V measurements, the significant dynamic contact angle change of Memb-PAMPSA-EG and Memb-PAMPSA-EG/DBSA gave a quantitative indication of the electrical tuneability of these membranes. All the membranes showed fouling removal ability under applied electrical potential and the fouling removal behaviour was closely related to the membrane conductivity. The results of this study open the pathway for the development of electrically responsive membranes for in situ control of fouling in membrane filtration systems.

Experimental investigation and mathematical modeling of nano‐composite membrane fabrication process: Focus on the role of solvent type

In this study, the effect of fabrication parameters on the performance of nano-SiO2-embedded membranes fabricated by three prevalent solvents was investigated. Genetic programming was applied for modeling and estimating the best preparation conditions to obtain a proper membrane for oily wastewater microfiltration. Membranes were prepared via a combination of vapor-induced phase separation and nonsolvent-induced phase separation methods. Different types of solvents such as N-methyl-2-pyrrolidone, N,N-dimethyl formamide, and dimethyl sulfoxide were used in cooperating with SiO2 nanoparticles to improve hydrophilicity properties of polyethersulfone. Thermodynamic behavior of solvents and their interaction with polymer and nonsolvent were considered as criteria for forming a suitable membrane with the maximum effectiveness of nanoparticles. The results showed that nanoparticles are more influential along with a solvent that has a weak affinity with a polymer, which subsequently can produce efficient membranes under conditions with a balance between exposure time and relative humidity. The optimum amounts of parameters were estimated by genetic algorithm to introduce a condition for having a membrane with the maximum permeate flux. Membranes fabricated with dimethyl sulfoxide represented the highest pore size and the most hydrophilic surface, which, in turn, led to the desired membrane (permeate flux 300L/m(2)hr and oil rejection 97%).

Superhydrophobic/Superoleophilic Polycarbonate/Carbon Nanotubes Porous Monolith for Selective Oil Adsorption from Water

A superhydrophobic/superoleophilic porous polycarbonate/carboxyl-functionalized multiwalled carbon nanotubes (PC/cMWCNTs) monolith with novel hierarchical micronanostructure was facilely fabricated via a thermally impacted nonsolvent induced phase separation method. A novel porous microstructure endowed PC/cMWCNTs monolith had a high porosity of 90.1%. Based on excellent superhydrophobicity (water contact angle of 159°) and superoleophilicity (oil contact angle of 0°), this porous monolith could selectively adsorb various types of oils/organic solvents from the oil–water mixture. Additionally, the monolith exhibited outstanding oil/water separation performance including fast adsorption speed, high saturation capacity, and superior recycling ability. The equilibrium adsorption time and saturated adsorption capacity of soybean oil were 20 s and 12.62 g g–1, respectively. By simple centrifugation or evaporation, the recovered PC/cMWCNTs monolith could be reused for at least 10 cycles. Thus, porous PC/cMWCNTs...

Free-standing polylactic acid/chitosan/molybdenum disulfide films with controllable visible-light photodegradation

The serious white pollution and energy crisis make it important and urgent to develop the degradable materials. The free-standing photodegradable PLA/CS/MoS2 composite films were successfully prepared with the non-solvent induced phase separation method. The morphology, FTIR, Raman, UV–vis, fluorescence and visible light photodegradation rates of the films were investigated. The prepared PLA/CS/MoS2 composite films could effectively absorb visible light, which were accompanied with photoluminescence. The photodegradation rates of the PLA/CS/MoS2 films could be easily tuned by changing MoS2 contents in a controlled way. The weight loss of the PLA/CS/MoS2 films could reach up to ∼22% after the visible light illuminating for 8 days, which were much faster than PLA/CS films. The films develop a new way to design a both photodegradable and biodegradable material, which can be used as excellent biomedical and packaging materials.

Macrovoid-free PES/SPSf/O-MWCNT ultrafiltration membranes with improved mechanical strength, antifouling and antibacterial properties

Macrovoid-free polyethersulfone/sulfonated polysulfone (PES/SPSf) ultrafiltration (UF) membranes containing oxidized multi-walled carbon nanotubes (O-MWCNTs) were fabricated via a non-solvent induced phase separation method using H2O and PEG 20 kDa as a non-solvent additives. The results show that the fully sponge-like morphology of the PES/SPSf membranes could be achieved as the content of O-MWCNTs in the casting solutions was increased, due to the formation of strong hydrogen bonds between SPSf, H2O, PEG 20 kDa and O-MWCNTs. Such morphology provided excellent mechanical strength properties with the highest of 4.02 ± 0.08 MPa obtained for the membrane containing 0.1 wt% O-MWCNTs. Microscopic analysis revealed homogenous distribution of O-MWCNTs in the PES/SPSf mixed-matrix membranes. Moreover, pure water flux initially increased from 598 to 713 L/m2 h followed by a decline to 590, 560, 553 and 578 L/m2 h as the content of O-MWCNTs was increased from 0 wt% to 0.005, 0.01, 0.03, 0.05 and 0.1 wt%, respectively. A rejection of > 99.9% for bovine serum albumin (BSA) was achieved by membranes containing 0.05 wt% O-MWCNTs. The water flux recovery ratio of membranes containing O-MWCNTs was found to be higher (> 90%) than that of pristine PES/SPSf (75%) even after the second fouling and cleaning stages. Furthermore, it was found that only 85% of E. coli bacteria were killed by pristine PES/SPSf, compared to 99% by PES/SPSf membrane containing the highest O-MWCNT loading. The fabricated flat-sheet membranes display attractive features for use as UF membranes in the pre-treatment stage of water treatment.

Superhydrophobic and Antibacterial Properties of Cotton Fabrics Treated with PVDF and nano-ZnO through Phase Inversion Process

Cotton fabrics exhibiting superhydrophobic and antibacterial properties were prepared through a non-solvent induced phase separation method using hydrophobic poly(vinylidene fluoride) (PVDF) and its hybrids with photocatalytic zinc oxide nanoparticles (nano-ZnO) as surface modifying agents for cotton fabric. The effects of coagulating medium and temperature on microstructural morphology and surface hydrophobictity of the cotton fabrics were investigated by FE-SEM observation and contact angle measurement. Superhydrophobic cotton fabrics exhibiting water contact angle higher than 150 ° could be obtained by coating the fabrics with solutions of PVDF and nano-ZnO followed by coagulation in ethanol as non-solvent. This phenomenon is considered to be originated from both chemically hydrophobic PVDF layer and physical micro- and nano-bumps formed on the surface of cotton fabric, which are essential requirements for Lotus effect. Moreover, antibacterial properties could be synergistically obtained by utilizing photocatalytic effect of nano-ZnO.

Efficient preparation of a novel PVDF antifouling membrane based on the solvent-responsive cleaning properties

Abstract In this paper, zein was first used as a stimuli-responsive anti-fouling medium to improve the fouling release ability of polyvinylidene fluoride (PVDF) ultrafiltration membranes based on the dissolution properties of zein in various solvent systems. The PVDF/zein blend membrane was prepared by the conventional non-solvent induced phase separation (NIPS) method, and the zein component was introduced into the modified PVDF membrane matrix without decreasing the separation performance. The solvent with a low concentration for zein was used as the cleaning agent to clean the fouled membranes, and the modified PVDF membrane could exhibit a very high water flux recovery ratio (＞95%) with the enhanced fouling release ability. Based on the solvent response characteristics, the preferential adsorption properties of zein for organic solvents such as ethanol and acetone made it preferentially swell in the cleaning agent to change the interfacial properties of the modified PVDF membrane and made pollutants easier to be removed by destroying the physical and chemical attachment of pollutants on the surface and pores of the fouled membranes. This article aims to provide a convenient way to improve the antifouling and long-term separation performances of the porous separation membranes.

THERMODYNAMIC STUDY OF POLYMER ELECTROLYTE MEMBRANE PREPARATION BY NON-SOLVENT INDUCED PHASE SEPARATION

The composition of both the polymer solution and the non-solvent determines the resulted membrane morphology during membrane preparation through non-solvent induced phase separation (NIPS) method. In the porous polymer electrolyte membranes (PEMs), a specified porosity and uniform pore membranes are required; therefore prediction of membrane morphology is essential. The Dimensional parameter of thermodynamic was determined to find the diffusional rate between DMAc solvent and Water nonsolvent during the membranes preparation. The influences of the addition of nano-clay as filler and polyvinylpyrrolidone (PVP) addition as pore-forming agent on the thermodynamic parameter were investigated. The resulted nanocomposites were characterized by measuring their porosity and electrolyte uptake as well as by a scanning electron microscopy. The composition of non-solvent required to induce phase separation of the casting solution was determined by cloud point experiment. By adding the content of additives the binodal line shifts to polymer/solvent axis, moreover MG reduces and DSBC raises and the thermodynamic parameter increased. It was obtained that the solubility parameters (Di/j) between solvent-additive are DDMAc/nano-clay = 0.787 (MPa0.5), DPVP/DMAc = 5.536 (MPa0.5), and The Interaction parameters (c) are cDMAc/nano-clay = 1.661 (MPa0.5), cDMAc/PVP = 1.449 (MPa0.5).

Blending based polyacrylonitrile/poly(vinyl alcohol) membrane for rechargeable lithium ion batteries

A gel polymer electrolyte based on polyacrylonitrile (PAN)/poly(vinyl alcohol) (PVA) blending membrane have been fabricated through non-solvent induced phase separation (NIPS) method followed by activation in liquid electrolyte of 1.0 M LiPF6 in carbonate solvent. The blending compatibility of PVA/PAN is investigated through thermodynamics analyses and demonstrates the miscibility of PAN/PVA blending system. The blending membranes with weight ratio of PVA/PAN= 10:90 and 20:80 have great effect on morphology of both top and bottom surface. This characteristic exhibits the high electrolyte uptake (up to 585%), acceptable thermal stability, excellent ionic conductivity and electrochemical stability (up to 5.28 V). The application of PAN/PVA blending membrane has been demonstrated by a coin cell using Li metal as counter electrode at 1C, resulting in better long-term cycle stability in comparison to cells with Celgard2320 separator and the highest capacity retention of 96%.

Development of advanced nanocomposite membranes using graphene nanoribbons and nanosheets for water treatment

Water-intensive industries have to comply with stringent environmental regulations and evolving regulatory frameworks requiring the development of new technologies for water recycling. Development of polymeric membranes may provide an effective solution to improve water recycling, but require finely-tuned pore size and surface chemistry for ionic and molecular sieving to be efficient. Additionally, fouling is a major challenge that limits the practical application of the membranes in water recycling in these industries. In this work, four different graphene oxide (GO) derivatives were incorporated into a polyethersulfone (PES) matrix via a non-solvent induced phase separation (NIPS) method. The GO derivatives used have different shapes (nanosheets vs nanoribbons) and different oxidation states (C/O = 1.05–8.01) with the potential to enhance water flux and suppress fouling of the membranes through controlled pore size, hydrophilicity, and surface charge. The permeation properties of the PES/GO membranes were evaluated using a water sample from the Athabasca oil sands of Alberta. The results for contact angle and streaming potential measurements indicate the formation of more hydrophilic and negatively charged PES/GO nanocomposite membranes. All graphene-based nanocomposite membranes demonstrated better water flux and rejection of organic matter compared to the unmodified PES membrane. The fouling measurement results revealed that fouling was impeded due to enhanced membrane surface properties. Longitudinally unzipped graphene oxide nanoribbons (GONR-L) at an optimum loading of 0.1 wt% (wt%) provided the maximum water flux (70 LMH at 60 psi), organic matter rejection (59%) and antifouling properties (30% improvement compared to pristine PES membrane). Flux recovery ratio experiments indicated a remarkable enhancement in the fouling resistance property of PES/GO nanocomposite membranes.

Nonsolvent-induced phase separation synthesis of superhydrophobic coatings composed of polyvinylidene difluoride microspheres with tunable size and roughness

Polyvinylidene difluoride (PVDF) microspheres are synthesized using the non-solvent induced phase separation (NIPS) method. The diameters of the microspheres are varied from 0.3 μm to 2.8 μm by controlling the amount of water added to a solution of PVDF in dimethylformamide. Sphere aggregates are created from spun-on films whose thickness is tuned in the range 6.5–16.5 μm by varying the spin-casting rotational velocity. Spin-casting with optimized parameters results in high-surface-area films that are among the most superhydrophobic non-templated polymer coatings to date, with water contact angles up to 171°, hysteresis less than 12°, and slide angle as low as 3°. We model the dependence of sessile water contact angle on the morphological properties of the films, including not only the sphere diameter, but also nanoscale roughness of the microsphere surfaces and the geometries of macroscopic fingers formed by the aggregated spheres.

Preparation of PSF/FEP mixed matrix membrane with super hydrophobic surface for efficient water-in-oil emulsion separation.

Polysulfone (PSF)/fluorinated ethylene propylene (FEP) mixed matrix membranes (MMMs) with super hydrophobic surface were successfully fabricated via non-solvent induced phase separation (NIPS) method. The effects of FEP content on the morphology, roughness, wettability, pore size, and mechanical property of PSF/FEP MMMs were characterized by scanning electron microscope, confocal microscopy, contact angle goniometer, mercury porosimetry, and tensile testing instrument, respectively. When the FEP content was 9 wt%, the average roughness of M-4 reached 0.712 μm. Meanwhile, the water contact angle (CA) and the water sliding angle (SA) was 153.3° and 6.1°, respectively. M-4 showed super hydrophobicity with a micro- and nanoscale structure surface. Then, M-4 was used for separating of water-in-oil emulsion, showing high separation efficiency for water-in-kerosene and water-in-diesel emulsions of 99.79% and 99.47%, respectively. The flux and separation efficiency changed slightly after 10 cycles. Therefore, this study indicated that the obtained PSF/FEP MMM with super hydrophobic surface could be used for efficient water-in-oil emulsion separation.

A gel polymer electrolyte based on Polyacrylonitrile/organic montmorillonite membrane exhibiting dense structure for lithium ion battery

Polyacrylonitrile (PAN)/organic montmorillonite (OMMT) membranes served as a host which is swelled using a liquid electrolyte of 1.0M LiPF6 in carbonate solvent for gel polymer electrolyte have been fabricated by non-solvent induced phase separation (NIPS) method. The OMMT fillers have affected the morphology, thermal stability, electrolyte uptake, ionic conductivity and electrochemical properties of PAN/OMMT membranes in different ways. The PAN/OMMT membrane exhibits high liquid uptake (375.5%), superior dimensional stability under 150°C for 15min and superior electrochemical stability up to 4.62V. Moreover, the gel polymer electrolyte based on PAN/OMMT membrane not only possesses lower polarization and interfacial resistance, but also effectively suppresses the formation of Li dendrites as reflected in the surface morphology of lithium anode after cycling test. The application of natural montmorillonite has been demonstrated by a coin cell using Li metal as counter electrode at 1C, resulting in the high capacity of 141mAhg−1 after 100cycles and high capacity retention of 95.9%. The possibility of PAN/OMMT membrane applied for the sustainable safety lithium ion battery can be realized.

Novel ultrafiltration membranes with excellent antifouling properties and chlorine resistance using a poly(vinyl chloride)-based copolymer

Novel antifouling and chlorine-resistant ultrafiltration membranes were successfully fabricated using poly(vinyl chloride-co-acrylonitrile-co-sodium 4-styrenesulfonate) (PVC-PAN-PSS), a novel poly(vinyl chloride)-based copolymer, via a non-solvent induced phase separation (NIPS) method. Quartz crystal microbalance data revealed reduced levels of bovine serum albumin (BSA) adsorption on PVC-PAN-PSS films when compared to those of pure poly(vinyl chloride) and polyacrylonitrile films. The morphologies, chemical compositions, surface roughness and hydrophilicity of the membrane surfaces were characterized by field-emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle goniometer, respectively. The hydrophilicity and antifouling properties of the membranes were clearly shown to increase with increasing level of poly(sodium 4-styrene-sulfonate) (PSS) in the copolymer; the membrane with 2wt% PSS exhibited the best antifouling properties, namely ~99% of flux recovery ratio for humic acid (1.0gL−1). Furthermore, the pore structures and antifouling properties of the PVC-PAN-PSS ultrafiltration membranes were maintained after soaking in 1000ppm sodium hypochlorite for 168h, while common membrane additives such as methacryloyloxyethylphosphorylcholine-co-poly(propylene glycol) methacrylate and Pluronic® F-127 were rapidly degraded in this oxidizing environment. PVC-PAN-PSS is expected to be a promising ultrafiltration membrane material with both superior antifouling properties and excellent chlorine resistance.