Vapor-induced Phase Separation Research Articles

Double stimuli-responsive isoporous block copolymer membranes upon phase separation strategies

Isoporous membranes from block copolymer commonly involves in the self-assembly and non-solvent induced phase separation (SNIPS), which could improve the selectivity and water permeance. However, such strategy face challenges: (1) to prepare poly (acrylic acid) PAA based block copolymer isoporous membrane with SNIPS method is difficult since PAA is extremely hydrophilic; (2) large consumption of block copolymer and non-solvent (water) might limit its application. Herein, isoporous membranes from Polystyrene-block-poly (acrylic acid) (PS-b-PAA) were well prepared with amine terminated poly(N-isopropylacrylamide) (pNIPAM-NH2) through the SNIPS and the airflow accelerated evaporation induced phase separation methods (acEIPS). Such membranes bear not only regularity in morphological structure, but also high water permeance (1500 L h−1 m−2 bar−1 for the SNIPS, and 3000 L h−1 m−2 bar−1 for the acEIPS). With the participation of pNIPAM-NH2 the consumption of the block copolymer is limited to 7.8 wt % for the SNIPS method, and even to 5.3 wt % for the acEIPS method without non-solvent precipitation process. Besides, the membrane exhibits pH and thermal responsiveness.

Flexible multisensory sensor based on hierarchically porous ionic liquids/thermoplastic polyurethane composites

With the rapid development of wearable electronics and electronic skins, the demand for portable and flexible sensors that can perceive surrounding information, including mechanical forces, temperature, and humidity, is dramatically increasing. Herein, we develop a lightweight and flexible multisensory sensor based on the hierarchically porous ionic liquids (ILs)/thermoplastic polyurethane (TPU) composite by the combination of vapor-induced phase separation technique and ultrasound-assisted anchoring technique. The as-prepared porous TPU@ILs sensor possesses both the strain- and temperature- sensing capabilities. As a strain sensor, it exhibits excellent sensing performance in various aspects, such as ultra-low detection limit (0.5%), ultra-wide sensing range (0.5–600%), fast response/recovery time (100 ms/80 ms), and outstanding durability, attributed to the hierarchically porous microstructure of TPU@ILs composites. Due to the rigid conductivity-temperature dependence of ILs, the designed porous TPU@ILs sensor also possesses outstanding temperature sensing capability, which has both the high temperature resolution (0.05 °C) and ultrawide temperature sensing range (−30–80 °C). This work provides an effective but simple strategy to fabricate high-performance multisensory sensors, which have great potentials in electronic skins and wearable electronics.

Underwater superoleophobic poly(vinylidene fluoride)/poly(N-isopropylacrylamide) membranes for highly efficient oil-in-water emulsion separation

Superoleophobic and anti-oil adhesion behavior has been considered the central character of the materials for removing oil from wastewater. Herein, poly(vinylidene fluoride)/poly(N-isopropylacrylamide) (PVDF/PNIPAM) membranes were fabricated by vapor-induced phase separation (VIPS) and then further post-modified by deposition of sulfonated dopamine (SDA). The resulting membrane has a strong underwater superoleophobicity with an underwater toluene contact angle of 163 ± 2° and an ultralow adhesion force (1.9 ± 0.02 µN) between the surface and the oil. Therefore, it can efficiently remove emulsified toluene from water with a flux of 2211 ± 80 L m−2 h−1 bar−1 and an oil rejection of 99.5 ± 0.4%. This work offers a novel technique for the fabrication of porous membranes with excellent anti-oil fouling performance which will be practically used in the treatment of emulsified oils.

Metal-organic framework/H2O2-exfoliated g-C3N4/poly(vinylidene fluoride) composite nanofiltration membranes

In this current work, a proper membrane was fabricated via vapor induced phase separation (VIPS) coupled with the non-solvent induced phase separation (NIPS). First, synthesized hydrogen peroxide treated exfoliated graphitic carbon nitride (H2O2-g-eC3N4) nanosheets were incorporated into the mixed matrix membrane (MMM). Then, synthesized NH2-MIL-101(Al) nanoparticles were incorporated into the MMM. In the next step, the synergistic effect of NH2-MIL-101(Al) and H2O2-g-eC3N4 was investigated systematically, and the optimized proportion of each modifier was acquired. The optimized membrane elucidated a high flux rate that reached as high as 20.7 ± 1.01 L m−2 h−1.bar−1, which was almost 62% higher than pristine PVDF membrane. It came across that the optimum membrane could provide a high dye rejection properties (99.9%, 99.8%, 99.7%, 99.3%) for orange G (OG), sunset yellow FCF (SY), naphthol yellow S (NYS), and Martius yellow (MY), respectively. Significant antifouling feature (96% for the optimum membrane), and outstanding long-term stability. Moreover, it was found that the synergistic effect of used dual nanoparticle/nanosheet caused promising long rejection stability even after 12 days.

3D helical membranes for process intensification of membrane separation via generation of Dean vortices

A novel three-dimensional (3D) helical membrane is developed for process intensification via generation of Dean vortices in helical membrane channel. 3D helical porous polyethersulfone membrane is fabricated by casting the membrane forming solution on the surface of 3D-printed porous substrate with a 3D helical channel structure by high-speed rotation method, and then curing by vapor-induced phase separation. The optimal helical radius and internal channel height are both 19 mm for the prepared 3D helical membranes. When the feed flowrate is higher than the minimum critical flowrate, Dean vortices can be easily generated in the 3D helical membrane channel, and thus the membrane fouling can be effectively mitigated. The ratio of average transmembrane flux of 3D helical membrane to that of conventional cylindrical membrane increases from 1.0 to ∼2.0 when the feed flowrate increases from 2.1 to 106.1 mm s−1, and from 1.0 to ∼1.9 when the feed particle concentration increases from 0 to 20 g L−1. No matter how the microstructures of particles in feed solutions vary, Dean vortices generated in 3D helical membrane channels are always efficient to diminish the particle deposition on membrane surface. The proposed strategy is highly promising for developing efficient membranes with different materials for various applications.

Immobilization of TiO2 nanoparticles on PES substrate via dopamine and poly (vinyl alcohol) for long-term oil/water purification

In this paper, a facile procedure is presented to prepare a membrane with antifouling properties based on Tio2 and polyvinyl alcohol hydrophilicity and the high adhesion of dopamine. First, vapor-induced phase separation was used to prepare the PES substrate, and then TiO2 nanoparticles were anchored on the membrane surface with the assistance of dopamine and PVA. The nanoparticles were uniformly immobilized on membrane surface, significantly advancing the performance of the PES membrane. Results of contact angle measurements revealed an outstanding improvement in the surface hydrophilicity. The fabricated membranes had higher water permeation during oil/water separation and also greater oil rejection with approximately 50% improvement compared with the pristine membrane. Moreover, a FRR of 81% after fouling with oil droplets, increasing in subsequent cycles to 87%, showing a good regeneration capability during long-term performance was achieved by the modified membrane, which confirms the low fouling tendency. Stability of NPs was investigated through a cross-flow water flux, followed by weight measurements, FE-SEM and EDX analysis prior and after the flux. The results proved the stability of modifiers on the membrane surface.

High‐Performance Biomechanical Energy Harvester Enabled by Switching Interfacial Adhesion via Hydrogen Bonding and Phase Separation (Adv. Funct. Mater. 38/2022)

Biomechanical Energy Harvesters In article number 2204304, William W. Yu, Wen Jung Li, Walid A. Daoud, and co-workers demonstrate a high-performance flexible biomechanical energy harvester by switching its interfacial adhesion via hydrogen bonding interactions and solvent evaporation induced phase separation. This wearable power source can generate a record high peak power density of 20.5 W m−2 Hz−1 under a low biomechanical input of 5 N, and can sufficiently power small electronics through harvesting regular or intermittent human motions.

Complex Suspended Janus Droplets Constructed through Solvent Evaporation-Induced Phase Separation at the Air-Liquid Interface.

Phase separation technology has attracted extensive scientific interest because of its intriguing structure changes during the phase separation process. Phase separation inside emulsion droplets in continuous surroundings has been well studied in recent years. Many investigations have also been conducted to study the droplet phase separation phenomena in noncontinuous surroundings. However, studies on the phase separation phenomena and the spreading behavior of suspended droplets at the air-liquid interface were rarely reported. In this study, PEGDA-glycerol suspended Janus droplets with a patchy structure were produced by utilizing solvent evaporation-induced droplet phase separation at the air-liquid interface. By altering the glycerol/PEGDA volume ratio, the initial proportion of ethanol, and the concentration of surfactants, suspended droplets with different morphologies can be achieved, which include filbert-shaped droplets (FSDs), half lotus seedpod single-phase Janus droplets (HLSDs), lotus seedpod single-phase Janus droplets (LSDs), lotus seedpod-shaped droplets (LSSDs), multiple-bulge droplets (MBDs), and half gourd-shaped droplets (HGSDs). A patchy structure was generated at the air-droplet interface, which was attributed to the Marangoni stresses induced by nonuniform evaporation. Furthermore, a modified spreading coefficient theory was constructed and verified to illustrate the phase separation at the air-droplet interface, which was the first research to predict the phase separation phenomena at the air-liquid interface via spreading coefficients theory. Moreover, we studied the factors that led to the droplets being able to float by designing the combined parameters, including three interfacial tensions and the equilibrium contact angles. Therefore, a simple and versatile strategy for creating suspended Janus droplets has been developed for the first time, which holds significant potential in a variety of applications for material synthesis, such as the electrospinning solution behavior when sprayed from the nozzle into the air.

Heavy metal removal using structured sorbents 3D printed from carbon nanotube-enriched polymer solutions

<h2>Summary</h2> Sorbents with structures tailored at the molecular through device scales are needed to meet the demand for separations that can isolate trace analytes from complex mixtures. Here, direct-ink-writing three-dimensional (3D) printing is combined with a surface-segregation and vapor-induced phase separation (SVIPS) process to create hierarchically structured sorbents that satisfy this criterion. Composite inks containing polysulfone, polystyrene-<i>block</i>-poly(acrylic acid) (PS-PAA), and carbon nanotubes (CNTs) were formulated to allow these processes to proceed simultaneously. Enriching the inks with CNTs modulated their rheological characteristics such that microstructured sorbents with permeabilities of ∼10⁵ L m⁻² h⁻¹ bar⁻¹ could be printed. The SVIPS process generated an interconnected network of PAA-lined nanopores whose chemistry was tailored to produce sorbents that recovered Co²⁺ selectively from mixtures of Co²⁺ and Li⁺ and efficiently treated sub-parts per million feed solutions under dynamic flow conditions. The versatile combination of 3D printing and SVIPS provides new strategies for manufacturing next-generation sorbents with structures controlled across multiple length scales.

Random/aligned electrospun PCL fibrous matrices with modified surface textures: Characterization and interactions with dermal fibroblasts and keratinocytes

Micro- or nano-surface topography of a biomaterial can improve various cellular activities for obtaining functional tissues. Electrospun fibers can gain further functionality when introduced topographic details to their surfaces. In this regard, we produced random and aligned polycaprolactone (PCL) micron/submicron fibers by the electrospinning method. Simultaneously, the surface structure of the fibers was altered by applying phase separation processes including non-solvent-induced phase separation (NIPS) and vapor-induced phase separation (VIPS) mechanisms. As a result, PCL fibers with porous, wrinkled, grooved, and crater-like morphology were obtained. Human dermal fibroblasts (BJ cells) and human keratinocytes (HS2) were cultured onto the fiber surfaces and the data were evaluated in terms of cell-material interactions. Results showed that not only the orientation of fibers but also fiber topography affected both cell-fiber and cell-cell interactions in different manners. It was observed that the wrinkled topography is the most suitable for both dermal fibroblasts and keratinocytes in terms of cell attachment and proliferation. We also concluded that cellular behavior was varied according to the morphology of the cells used. Morphological observations showed that HS2 cells proliferated more intensively on all surfaces compared to BJ cells. All these findings can be evaluated in terms of the design of tissue scaffolds, especially in skin tissue engineering.

A surfactant-free approach: Novel one-step ultrasonic nebulizer spray method to generate amphiphilic Janus particles

HypothesisA solvent evaporation-induced phase separation method, which is based on the preferential partitioning of two or more immiscible materials after solvent evaporation on providing heat, has been one of the main strategies for synthesis of Janus particles (JPs). Considering this approach, it should be possible to synthesize surfactant free-JPs in continuous flow by the ultrasonic nebulizer spray method. ExperimentsTwo polymers, polystyrene and polymethylmethacrylate, were dissolved in dichloromethane, and droplets of a precursor solution generated by an ultrasonic nebulizer were then conveyed through a borosilicate glass cylinder with two heating zones. The solvent evaporation-induced phase separation occurred in a single flow process, which resulted in the preferential partitioning of two incompatible polymers in the droplets, leading to the formation of the spherical bicompartmental JPs. FindingsThe successful fabrication of spherical JPs was observed at high polymer concentrations (1.5 and 2.0 wt%), and at elevated temperature (40–75 °C). The fluorescent compartmentalization of JPs was confirmed. Furthermore, the interfacial arrangement of JPs at oil–water interface was studied. A detailed explanation of theoretical prediction of interfacial configurations of JPs was provided. Lastly, the generated JPs were proved as Pickering stabilizers at the oil–water interface.

Low-energy-consumption fabrication of porous TPU/graphene composites for high-performance microwave absorption and the influence of Fe3O4 incorporation

Fabrication of lightweight, thin thickness, broad bandwidth, strong absorption, and lower filler loading materials are of great interest for microwave absorption. Herein, porous thermoplastic polyurethane (TPU) /graphene composites were successfully prepared via a facile vapor induced phase separation (VIPS) technique. Compared with TPU foam, the introduction of graphene endows the composites favorable microwave absorption ability. The optimized composite foam with 3 wt% graphene (TPU/G-3) exhibits extraordinary wave attenuation capacity with a minimum reflection loss (RL min ) value of − 51.86 dB and effective absorption bandwidth (EAB) of 4.28 dB (12.6–17.0 GHz) at the thickness of 3.1 mm. Microwave attenuation mechanism indicates that the remarkable microwave absorption ability derives from conduction loss, dipole polarization loss, interfacial polarization loss as well as multiple scattering. Incorporating the same amount of Fe 3 O 4 as graphene to TPU/G-3 endows the composites with the RL min of − 58.96 dB, which is slightly better than TPU/G-3 due to more favorable impedance matching. However, the matching thickness becomes much higher to about 8.0 mm, which is mainly attributed to bigger pores caused by Fe 3 O 4 . Moreover, the VIPS strategy provides insight into the fabrication of facile and lightweight polymer-based porous electromagnetic absorption materials. • Vapor induced phase separation method for preparation of TPU-based porous composites. • Graphene facilitates heterogeneous nucleation for smaller pores than TPU foam. • Graphene content of 3 wt% endows composite favorable microwave absorbing performance. • Fe 3 O 4 influences the process of vapor induced phase separation with bigger pores. • Fe 3 O 4 improves the reflection loss but increases matching thickness due to big pores.

Engineering sterilization-resistant and fouling-resistant porous membranes by the vapor-induced phase separation process using a sulfobetaine methacrylamide amphiphilic derivative

The in-situ modification of polyvinylidene fluoride (PVDF)-based membranes with zwitterionic copolymers for environmental applications remains challenging because of the large polarity difference between PVDF and zwitterionic materials. Besides, common zwitterionic units such as sulfobetaine methacrylate fail when exposed to elevated temperatures, limiting their range of applications in biomedical engineering. We designed an amphiphilic copolymer containing sulfobetaine methacrylamide (SBAA), styrene and ethylene glycol methyl ether methacrylate (EGMA) groups. Once the appropriate composition determined, membranes were prepared by vapor-induced phase separation (VIPS), a process permitting fine control over formation mechanisms, hence over the matrix structure. Sorption, mapping FT-IR and DSC tests indicated that even a low proportion of SBAA (< 10 mol%) in the P(S-r-EGMA-r-SBAA) copolymer significantly increases the proportion of non-freezable water and enhances the strength of the hydration layer, compared to a system containing styrene and EGMA groups only, P(S-r-EGMA). The modification also resulted in a large increase in membrane hydration capacity (> 550 mg/cm3 vs. < 25 mg/cm3 for the virgin membrane). Consequently, the zwitterionic copolymer could efficiently mitigate biofouling by fibrinogen (76% drop), Escherichia coli (99% decrease) or whole blood (82% reduction), even after a steam sterilization process, while the control zwitterionic sulfobetaine methacrylate material failed at maintaining its performances. Separation tests carried out with bacterial solutions revealed the ability of the zwitterionic copolymer to significantly decrease irreversible fouling (27%), compared to a commercial membrane (47%). All in all, their porous structure, hydration capacity and their ability to withstand steam sterilization make these novel porous zwitterionic membranes ideal candidates for biomedical (blood filtration) or environmental applications (water treatment).

High‐Performance Biomechanical Energy Harvester Enabled by Switching Interfacial Adhesion via Hydrogen Bonding and Phase Separation

AbstractDramatic advances in wearable electronics have triggered tremendous demands for wearable power sources. To mitigate the impact of CO2 emission on the environment caused by energy consumption, biomechanical energy harvesting for self‐powered wearable electronics offers a promising solution. The output power of devices largely relies on the surface charge density, where adhesion interfaces generate a higher amount than nonadhesion counterparts, yet unfavorable for wearable devices due to the large detachment force required. Thus, sustaining high surface charge density in an adhesion‐free interface represents a major challenge. Herein, by leveraging intermolecular interactions and solvent evaporation induced phase separation, a nonadhesion interface is successfully realized, minimizing the interfacial adhesion from 20 to 0 kPa. Importantly, benefiting from the induced nano/microscale topography upon phase separation, comparable surface charges are generated at the interface. Consequently, a high‐performance flexible biomechanical energy harvester featuring a record high peak power density of 20.5 W m‐2 Hz‐1 at low matching impedance of 1 MΩ is achieved under a low biomechanical input force of 5 N. The device can power small electronics by harvesting regular or intermittent biomechanical energy and illuminate light‐emitting diodes wired/wirelessly. This work provides a facile strategy for interfacial engineering toward efficient energy harvesting.

Preparation of loose nanofiltration PVDF membrane coated with dopamine and EPPTMS layers based on mussel inspired technique and ring-opening reaction via a facile VIPS-NIGPS method for dye separation applications

In this work, vapor-induced phase separation (VIPS) coupled with non-solvent induced gelation phase separation (NIGPS), in which water was used as an additive to tailor loose nanofiltration (NF) membrane, was utilized to obtain an optimized and smoother primer PVDF membrane for efficient dye separation. Next, a polydopamine (PDA) layer was formed through the Mussel-inspired technique on the surface of the as-prepared PVDF membrane. Subsequently, an epoxy-propoxypropyl-trimethoxysilane (EPPTMS) layer was also fabricated on the PDA layer in order to enhance hydrophilicity and rejection performance of the prepared membrane. It was demonstrated that through the addition of external H2O (4%), viscosity was escalated due to the pre-gelation. Moreover, the NIGPS-VIPS process resulted in better consolidation of PVDF chains during de-mixing process, and therefore, led to the improved porosity and surface pore size. After the formation of PDA and EPPTMS layers, extraordinary separation and flux performance were obtained. The permeation rate across the membrane was as high as 15.5 L.m−2.h−1.bar−1, and the rejections of Crystal violet (CV), Methylene blue (MB), Methyl green (MG), Reactive red 120 (RR), and Direct yellow (DY) dye solutions (0.2 g/L) by the prepared PVDF/PDA/EPPTMS membrane were 99.1%, 98.1%, 98.6%, 90.3%, and 97.3%, respectively. Moreover, flux recovery rate was also enhanced from 59.0% to 94.2%, which was about 60% enhancement. The optimum membrane also exhibited an outstanding long-term rejection and long-term flux. All the separation tests demonstrated the extraordinary performance of the optimum membrane for dye rejection applications.

Pyridinium functionalized poly(phthalazinone ether ketone) with pendant phenyl groups porous membranes for vanadium flow battery application by vapor induced phase separation

A novel porous membrane based on pyridinium-functionalized poly(phthalazinone ether ketone) with pendant phenyl groups (PyPPEK-P) is synthesized from poly(phthalazinone ether ketone) with benzyl chloride moieties by the vapor induced phase separation (VIPS) process. The membrane is used for vanadium redox flow batteries (VRFB). Pyridine is used as an amination reagent to improve the chemical stability of the membrane, and its successful introduction is experimentally confirmed. The structure and properties of the porous membrane are adjusted by VIPS to enhance the membrane performance when used in batteries. It is found that a lower temperature and a longer exposure time are beneficial to obtaining a large pore size in cross-section, while relative humidity exert a complex effect on the membrane structure. The PyPPEK-P membrane prepared by mixed NMP and DMAc solvents as casting solution exhibit the best battery performance. Compared with Nafion 115, the PyPPEK-P membrane display higher coulombic efficiency (97.2% vs. 96.8%), voltage efficiency (83.1% vs. 76.9%), and energy efficiency (81.0% vs. 76.8%) at a 140 mA cm−2 current density. After 1000 charge-discharge cycles, the PyPPEK-P membrane exhibit a low capacity-decay, while the battery performance do not decline. These observations indicate that PyPPEK-P porous membranes have good application prospects in VRFB.

Spheres Multiple Physical Network-Based Triboelectric Materials for Self-Powered Contactless Sensing.

Non-contact mode triboelectric nanogenerators effectively avoid physical contact between two triboelectric materials and achieve long-term reliable operation, providing broad application prospects in the field of self-powered sensing. However, the low surface charge density of triboelectric materials restricts application of contactless sensing. Herein, by controlling Rayleigh Instability deformation of the spinning jet and vapor-induced phase separation during electrostatic spinning, a polyvinylidene fluoride@Mxene (Ti3 C2 Tx ) composite film with spheres multiple physical network structures is prepared and utilized as the triboelectric material of a self-powered contactless sensor. The structure of the composite film and high conductivity of Ti3 C2 Tx provide triboelectric materials with high output performance (charge output and power output up to 128 µC m-2 and 200 µW cm-2 at 2Hz) and high output stability. The self-powered contactless sensor shows excellent speed sensitivity (1.175 Vs m-1 ). Additionally, it could accurately identify the motion states such as running (55mV), jumping (105mV), and walking (40mV) within the range of 70cm, and present the signals in different pop forms. This work lays a solid foundation for the development and application of high-performance triboelectric materials, and has guiding significance for the research of self-powered contactless sensing.

Using the dimethyl sulfoxide green solvent for the making of antifouling PEGylated membranes by the vapor-induced phase separation process

The toxicity of common solvents used in membrane fabrication threatens the environmental sustainability and questions the claim that membrane technology is a green separation technology. Therefore, there is a need for re-orienting membrane fabrication processes towards greener solutions, making use of less toxic, and possibly environmentally friendly solvents. We employed dimethyl sulfoxide (DMSO), a non-toxic solvent, to prepare casting solutions containing polyvinylidene fluoride and an antifouling random copolymer made of polystyrene and poly(ethylene glycol) methyl ether methacrylate (PS-r-PEGMA). Membranes were formed by vapor-induced phase separation (VIPS). They were shown to be homogeneous in terms of structure and surface chemistry (tested by mapping FT-IR), suggesting compatibility of the polymer/copolymer/solvent system and justifying the choice of DMSO. Membrane hydration was drastically improved after adding PS-r-PEGMA with a water contact angle falling from 140° to 47°. As a result, biofouling by Escherichia coli and whole blood was reduced by > 90% in static conditions. During several filtration cycles of a highly fouling Escherichia coli solution flux recovery ratio could be increased from 16% (pristine membrane) to 29% (PEGylated membrane). All in all, this study reveals that low-biofouling homogeneous porous membranes can be prepared by in-situ modification and the VIPS process using a greener approach than traditionally reported.

Fabrication of Polyacrylonitrile UF Membranes by VIPS Method with Acetone as Co-Solvent.

For the first time, a systematic study was carried out of the replacement of the low-volatility solvents N-methyl-2-pyrrolidone (NMP) or dimethylsulfoxide (DMSO) with the high-volatility solvent acetone in the casting solution of polyacrylonitrile (PAN). The effect of acetone’s presence in the casting solution on the performance of ultrafiltration membranes fabricated via vapor-induced phase separation (VIPS) was investigated. It was possible to replace 40% of NMP and 50% of DMSO with acetone, which resulted in the reduction of the casting solution viscosity from 70.6 down to 41.3 Pa∙s (20% PAN, NMP), and from 68.3 down to 20.6 Pa∙s (20% PAN, DMSO). It was found that 20 min of exposure to water vapor (relative humidity—85%) was sufficient to govern the phase separation, which was mainly induced by the water vapor. Regardless of the casting solution composition (15 or 20% PAN; DMSO or NMP), all membranes formed via VIPS possessed a sponge-like porous structure. The addition of acetone to the casting solution allowed the reduction of the transport pore size from 35–48 down to 8.5–25.6, depending on the casting solution composition. By varying the acetone content at constant polymer concentration, it was possible to decrease the molecular weight cut-off (MWCO) from 69 to 10 kg/mol. Membranes prepared from 20% PAN solution in an acetone/DMSO mixture had the lowest MWCO of 10 kg/mol with a water permeance of 5.1 L/(m2·h·bar).

Effect of Polymer Concentrations on Pores Mechanism in Electrospun Fibre

Advanced material science has resulted in materials with atomic-scale dimensions whose tremendous application includes filtration, drug delivery, membrane, sensor, and encapsulation. Nanoporous fibre has been formed using temperature-induced phase separation (TIPS) and vapour-induced phase separation (VIPS) mechanism, but polymer concentration has been underestimated in the electrospinning parameter. This work aims at showcasing the effect of electrospinning parameters including polymer concentration and resultant phases on pore formation on fibre. Pore formation in electrospun fibre was carried out by electrospinning expanded polystyrene (EPS). The surface morphology of the resulting nanoporous fibre was characterized with Scanning Electron Microscope (SEM) while the pore distribution was analyzed with a BET (Brunauer, Emmet, Teller) micromeritics analyzer. From the result, an increased concentration of polymer from 10 % decreased bead population to zero, meanwhile, bombardment with high electrostatic power resulted in beaded fibres at 10% and 15% w/v. Further increase in EPS concentration resulted in beadless fibres and electrospun 20% EPS fibre at 8.5 kV resulted in porous fibre with meso, micro and macropores. At 11.5 kV, pore dimension in fibre reduced with predominant pore width less than 100 nm. An increased voltage to 13.5 kV resulted in morphologies showing brittled fibre probably due to excess pores formed. Conclusively, polymer concentration moderates variables interaction that resulted in phase separation which controls fibre orientation. Therefore, pore formation does not solely depend on TIPS, VIPS, and breath figures but also polymer concentration.