Solvent Evaporation Time Research Articles

The influence of cellulose acetate butyrate membrane structure on CO2/N2 separation: effect of casting thickness and solvent exchange time

With the rapid growth of economics, carbon dioxide (CO2) gases are being emitted in bulk into the atmosphere contributing to the current global warming issues. Thus, membrane separation technology was implemented due to its notable benefits of simple operation, cost savings, and high efficiency in CO2 separation. In this study, the cellulose acetate butyrate (CAB) membrane was synthesized from CAB polymers of molecular weights (Mn) 12,000 and 65,000, while the effects of casting thickness and solvent evaporation time during membrane fabrication were studied. The optimal casting thickness and solvent evaporation time were obtained at 250 µm and 5 min respectively, whereas the CO2 permeance and CO2/N2 selectivity were obtained at 106.87 ± 1.03 GPU and 6.948 ± 0.081, respectively. Eventually, this newly developed CAB membrane is expected to benefit the industrial sectors by reducing the CO2 emissions with improved efficiencies in gas separation.

Effect of Reaction Temperature and Time on the Preferential Preparation of Cage Octamer and Decamer of Ammonium-Functionalized POSSs

Abstract In this study, the hydrolytic condensation of 3-(2-aminoethylamino)propyltrimethoxysilane and 3-aminopropyltrimethoxysilane was performed using aqueous trifluoromethanesulfonic acid (HOTf) as a catalyst and solvent at various setting temperatures and pressures in a Kugelrohr apparatus. The solvent evaporation time can be controlled by changing the pressure in the Kugelrohr apparatus. Ammonium-functionalized polyhedral oligomeric silsesquioxane (POSS) mixtures with high proportions of cage octamer (T8-POSS) were consequently obtained at lower setting temperatures (60 °C) in a Kugelrohr apparatus regardless of the solvent evaporation times (2–10 h). Meanwhile, using higher setting temperatures (100 °C and 120 °C) and longer solvent evaporation times (6–8 h), the proportion of cage decamer (T10-POSS) in the POSS mixture increased. Therefore, T10-POSS formed more easily than T8-POSS during reactions in which the solvent was evaporated at higher temperatures and for longer times.

Organic acids interacting with block copolymers have broadened the window that retains isoporous structures

Evaporation is significantly important for the preparation of isoporous membranes from self-assembly and non-solvent induced phase separation (SNIPS). Unfortunately, the time of solvent evaporation that retains isoporous structures is usually rather short, which causes many challenges to fabricate membranes with repeatable and controllable isoporous structures. In the current work, we used organic acids to tailor and enlarge the time window that led to isoporous structures, and their effects on membrane formation were investigated. It was found that binary and ternary organic acids all worked effectively and were able to extend the time window that produced isopores to longer than 200 s. In previous publications, this time duration was commonly in the range from several to tens of seconds. The nuclear magnetic resonance (NMR) determination implied that molecular cross-linking between acids and copolymers was existed in solution, and results from small angle X-ray scattering (SAXS) analysis demonstrated that the microphase separation of the block copolymer in casting solution was enhanced by the selected acids. The results proved that binary and ternary acids added to casting solution had not only enhanced the microphase separation but also stabilized the phase separated domains, which was ascribed as the reason for the extension of the time window. The effectiveness of organic acids on broadening the time window was also found for casting solutions of different concentrations and solvent compositions. Besides the role on stabilization of isoporous structure, the flux of isoporous membrane was also greatly increased by the organic acids.

Mesoporous TiO2 Microspheres with Precisely Controlled Crystallites and Architectures

Summary Mesoporous TiO2 nanomaterials have been investigated for decades; however, most endeavors have been focused on the exploration of their potentials in various applications, and the fundamental research for preparing mesoporous TiO2 in a highly controllable manner remains unfruitful. Herein, we report a facile pressure-driven oriented assembly approach to synthesize an unprecedented type of dehiscent mesoporous TiO2 microspheres with radial mesopore channels and oriented rutile crystallites. By varying the concentrated HCl amount, we have been able to produce TiO2 microspheres with well-controlled rutile/anatase phase ratio. By further manipulating the reaction conditions including solvent evaporation time and hydrothermal temperature, the oriented growth with tunable crevices can also be well manipulated. Such dehiscent mesoporous TiO2 microspheres have exhibited great permeability and excellent photocatalytic properties for H2 generation. We believe that the high structural complexity and predictability of this method offers great opportunities in enhancing the performance of TiO2-based materials.

Formation of Thin, Isoporous Block Copolymer Membranes by an Upscalable Profile Roller Coating Process-A Promising Way to Save Block Copolymer.

In this work we present a method to manufacture flat sheet membranes with a thin isoporous block copolymer (BCP) layer (thickness <3 µm) by profile roller coating (breadth: 30 cm) on top of a porous support membrane. Highly diluted BCP-solutions were used for this coating process. While we cast membranes with dimensions of 30 cm × 50 cm in this work, the procedure can easily be extended to endless dimensions in this roll to roll (R2R) process. The method offers the possibility to save >95% of BCP raw material compared to common doctor blade casting, by strongly decreasing the layer thickness to below 3 µm in combination with a highly open substructure. Additionally, we report a straightforward method to investigate the influence of the solvent evaporation time between coating and precipitation (phase inversion) on the membrane morphology using one sample only, which also ensures that all other influencing parameters remain constant.

Continuous synthesis of high quality metal–organic framework HKUST-1 crystals and composites via aerosol-assisted synthesis

Highly crystalline metal–organic framework (MOF) crystals are desirable for their practical applications and synthesized predominantly using batch processes that are less scalable. More scalable continuous processes for MOF synthesis such as spray-drying and aerosol-assisted synthesis have been recently developed. However, these techniques often resulted in poorly crystalline nanoparticles and their assemblies primarily due to extremely short (sub-second) crystallization time and fast solvent evaporation. Here we report facile continuous aerosol-assisted production of highly crystalline HKUST-1 crystals with relatively narrow size distributions as well as their composites with both inorganic and organic materials exhibiting unique microstructures. Solvents with high donor numbers and low vapor pressures were found desirable to increase both crystallization and solvent evaporation times. Dimethyl sulfoxide (DMSO) was used as a co-solvent with DMF to form phase-pure high quality HKUST-1 crystals revealed by SEM, XRD, and N2 adsorption. Furthermore, alumina nanoparticles and polyethersulfone (PES) polymer were incorporated to create unique microstructures.

Menthol-loaded PLGA Micro and Nanospheres: Synthesis, Characterization and Degradation in Artificial Saliva

Menthol-loaded PLGA micro/nanospheres were synthesized using the multiple emulsion/solvent evaporation technique. Parameters such as stirring rate, external surfactant content, PLGA/menthol weight ratio, solvent evaporation and lyophilization time were evaluated as well as the degradation of micro/nanospheres in an artificial saliva medium. The menthol/PLGA micro/nanospheres thus obtained had a size distribution of between 217 nm and 13 µm and particles with spherical and dense morphology were evidenced by SEM micrographs. FTIR and TGA data showed an increase up to 60% of menthol incorporated in the micro/nanoparticles. The degradation of menthol-loaded PLGA micro/nanoparticles in artificial saliva significantly affected the particles morphology and appears to be an effective medium for releasing menthol.

Nanofiltration membranes based on PA6/EVOH with variable composition and morphology

Nanofiltration PA6/EVOH membranes were prepared through a nonsolvent induced phase separation technique. The effects of polymer concentration in the solution and solvent evaporation time on the performance and morphology of the resulting membranes were investigated by cloud point titration, permeation, and scanning electron microscopy (SEM). Experimental cloud point data for various prepared membranes suggested that polymer solutions with higher concentrations of PA6/EVOH need a less content of nonsolvent. SEM observations show that an increase in polymer concentration leads to formation of a thin dense layer on the surface of the membrane thanks to pore size reduction. However, dense top layer of membrane becomes thicker as polymer concentration increases from 15 wt% to 20 wt%. The performance of membranes reveals a decrease with polymer concentration in casting solution. By contrast, Polyamide/Poly(ethylene‐co‐vinyl alcohol) membranes show an optimal performance with various formic acid evaporation times. J. VINYL ADDIT. TECHNOL., 25:E28–E34, 2019. © 2018 Society of Plastics Engineers

Preparation and characterization of hydrophilic surface modifier macromolecule modified poly (ether sulfone) photocatalytic membrane for phenol removal

A modified poly (ether sulfone) (PES) by hydrophilic surface modifying macromolecules (LSMM) incorporated with oxygenated graphitic carbon nitride (OGCN) photocatalyst (PES/OGCN-LSMM) was successfully prepared as a hybrid photocatalytic membrane. The effect of solvent evaporation time during membrane fabrication was studied by focusing on the positioning of LSMM in order to provide the desirable properties of the PES/OGCN-LSMM hybrid membrane for phenol removal performance by photocatalytic and separation. The PES/OGCN-LSMM membranes exhibited a decreased value of contact angle as the solvent evaporation time increased. The SEM images revealed a dense top layer supported by finger-like structures underneath, which was formed for the membranes at 0–4 min solvent evaporation time, while a sponge-like microvoid structure was observed at 5 min of solvent evaporation time. It is interesting to highlight that as the evaporation time increased, the pure water flux decreased as the result of compact denser membrane. Benefitting the special feature of LSMM that tends to migrate upwards upon mixing, the LSMM effectively assisted OGCN photocatalyst to the top layer of the membrane. This was revealed by SEM top surface images that more OGCN photocatalyst particles were seen distributed on the dense top layer of the membrane upon longer solvent evaporation time supported by the membrane topography analysis. It was found that the phenol reduction by rejection and photocatalytic tests was the highest at 5 min solvent evaporation time, whilst water flux was the lowest. The obtained results showed that the LSMM has indeed assisted the positioning of OGCN towards the top layer of the membrane and consequently increased the photocatalytic activity of the membrane on phenol.

Influence of Solvent–Evaporation Effect on the Structure and Properties of PVDF-g-PNIPAAm Membranes

ABSTRACTTemperature-sensitive poly(vinylidene fluoride)-graft-poly(N-isopropylacrylamide)(PVDF-g-PNIPAAm) copolymer was synthesized and its flat membranes were prepared through phase inversion method with mixture of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF) as solvent in water coagulation bath. The effects of “open time” (solvent–evaporation time) on the structure and performance of membranes were investigated by X-ray photoelectron spectroscopy, field-emission scanning electronic microscopy, contact angle, filtration experiments and static protein adsorption. It was found that the increasing “open time” endowed the membrane with more pores on the surface, higher flux and better hydrophilicity, provided the membrane with lower protein adsorption. Thus, the copolymer membranes showed a good antiprotein fouling.

Tuning of Preparational Factors Affecting the Morphological Structure and Gas Separation Property of Asymmetric Polysulfone Membranes

The aim of this work was to study the effect of preparational factors such as solvent type, evaporation time (ET) and non-solvent additive, on the morphological structure, physical and gas separation properties of the prepared membrane samples by tuning of these parameters. Flat sheet asymmetric polysulfone (PSF) membranes were prepared by the dry/wet phase inversion process combined with the double coagulation bath method. The alteration of the prepared membranes were analyzed through scientific techniques such as Scanning Electron Microscope (SEM) and Dynamic Mechanical Thermal Analysis (DMTA). Furthermore, gas separation performance of membrane samples was measured in term of gas permeation and ideal selectivity of CO2/CH4. Experimental results showed that the change of preparational factors affected to the gas permeation of asymmetric PSF membranes. For example, the selective layer thickness increased with increasing of ET. This lead to increase significantly of ideal selectivity of CO2/CH4. The CO2/CH4 ideal selectivity was also increased with increase of ethanol (non-solvent additive) concentration in casting solution. In summary, the tuning of preparational factors affected to morphological structure, physical and gas separation properties of PSF membranes.

Solution Processing with a Good Solvent Additive for Highly Reliable Organic Thin-Film Transistors

High-performance transistors require homogeneous crystalline thin films with high charge carrier mobilities on large substrates. We report a versatile solution process that uses a good solvent additive with a high boiling point. This method enables the fabrication of uniform, large-area, polymer thin films with improved thin film crystallinity and electrical characteristics and high reliability organic transistors. We demonstrate here that the addition of a small amount of a good solvent additive with a high boiling point to the processing solution is highly effective in not only inducing the strong self-assembly of the conjugated polymer during film solidification by increasing the solvent evaporation time but also in ensuring the formation of a uniform film morphology. These characteristics were found to enhance the device performance of a poly(3-hexylthiophene) film processed from a mixed solvent containing chlorobenzene and 1,2,4-trichlorobenzene, which was found to exhibit a highest average field-eff...

Improvement of CO2/N2 separation performance by polymer matrix cellulose acetate butyrate

With the rapid development of modern civilization, carbon dioxide (CO2) is produced in large quantities and mainly generated from industrial sectors. The gas emission is the major contributor to global warming. To address this issue, the membrane technology is implemented for the CO2 removal, due to the energy efficiency and economic advantages presented. Cellulose acetate butyrate (CAB) is selected as the polymeric material, due to the excellent film-forming properties and capable of developing a defect-free layer of neat membrane. This study described the fabrication development of CAB using a wet phase inversion method with different casting conditions. Where the composition of the casting solutions (3-5 wt %) and solvent evaporation time (4-6 min) were determined. The outcomes of these dominant parameters were then used to determine the best CAB membrane for CO2/Nitrogen (N2) separation and supported by the characterization i.e. scanning electron micrograph. Gas permeation measurements showed satisfactory performance for CAB membrane fabricated with 5 min evaporation time and 4 wt% polymer composition (M2). Where, its permeance and selectivity are 120.19 GPU and 3.17, respectively. In summary, this study showed a brief outlined of the future direction and perspective of CAB membrane for CO2/N2 separation.

Improved performance of organic photovoltaic cells with PTB7-Th:PC71 BM by optimized solvent evaporation time in electrospray deposition

As poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b; 4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] has good potential as a low-band gap donor polymer for organic photovoltaic cells (OPVs), we investigated the optimized electrospray deposition condition for realizing suitable polymer ordering and/or crystallite size by controlling the solvent evaporation time. Previous studies on the electrospray process have mainly focused on novel device structure owing to its unique characteristic of small droplet size, which is less than 1 μm. However, in this research, we investigated the spontaneous formation of interpenetrating continuous networks of the donor- and acceptor-rich domains of solvent evaporation during the electrospray process. By evaluating the ultraviolet–visible absorption spectrum, Raman spectroscopy, and direction of polymer ordering, it was shown that the polymer-stacking condition was not influenced by solvent evaporation time, even though poly(3-hexylthiophene-2,5-diyl) along the face-on direction was well stacked under the slow solvent evaporation condition. In contrast, the crystallite size, which was estimated from the full width at half maximum X-ray diffraction pattern, increased as the solvent evaporation time increased. This means that the crystalline grain spontaneously grew in the droplet and that the large crystalline grain was formed during the slow evaporation condition. Furthermore, the photovoltaic performance trend was the same as the performance trend of the crystallite size and were increased with increasing solvent evaporation time for both polymers. Therefore, the crystalline grain size was a dominant factor in determining the photovoltaic performance. Additionally, the crystalline grain size could be controlled by the solvent evaporation time. Finally, by optimizing the active-layer thickness, the highest photoconversion efficiency of 8.6% was achieved. This is the highest value of an electrospray-based device. These results indicate that the solvent evaporation time is an important factor in determining the crystallite size of an organic thin film, which directly affects the photoconversion efficiency of OPVs.

Characterization and application of cellulose acetate synthesized from sugarcane bagasse

The synthesis and application of cellulose acetate (CA) from sugarcane bagasse were investigated. Firstly, cellulose was extracted by a sequential treatment with H2SO4 (10% v/v), NaOH (5% w/v), EDTA (0.5% w/V), and H2O2 (5% v/v), and characterized by X-ray diffraction (DRX). After the acetylation of the extracted cellulose, CA was characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA), and was applied in the membrane production. The membranes were analyzed by DSC and atomic force microscopy (AFM), and tested in the flux of water vapor to determinate the best conditions for membrane manufacturing. FTIR analysis proved the replacement of free OH groups by acetyl groups, and the thermal analysis showed that sugarcane bagasse CA possessed thermal properties compared to commercial grade CA. The best conditions to prepare membrane were: 3% (w/v) of polymer/solvent relation, 10min of solvent evaporation time, and 20°C as temperature for the coagulation bath. These results show that CA can be successfully synthesized from sugarcane bagasse and applied in membrane preparation.

Effect of combination dope composition and evaporation time on the separation performance of cellulose acetate membrane for demak brackish water treatment

The coastal areas in Indonesia often have a problem of clean water lack, because the water is classified as brackish water. Therefore, this research investigated the fabrication of CA membranes using phase inversion method for brackish water treatment. Investigation was conducted to study the effect of combination dope composition and evaporation time on separation performance and morphology of the memrbane. Membrane was fabricated by dry-wet phase inversion technique with variation of polymer concentration 17, 18 and 20 wt% in the total solid and evaporation time of 5, 10 and 15 seconds, respectively. The asymmetric membranes were characterized by permeability test through rejection and flux measurements using brackish water as feed. The experimental results from SEM images analysis showed that all the membranes have a thin small porous layer and thicker sub-structure of larger porous layer formed asymmetric membrane. Moreover, the greater polymer concentration is resulting smaller pore size and smaller membrane porosity. The longer evaporation time was also resulted in denser membrane active layer. The best membrane performance was observed at the composition of 20 wt% CA polymer, 1 wt % polyethylene glycol with the solvent evaporation time of 15 seconds.

Highly efficient organic photovoltaic cells fabricated by electrospray deposition using a non‐halogenated solution

Since a large amount of solvents are needed for roll‐to‐roll printing processes of organic photovoltaic cells, an environmentally friendly process for practical mass production systems is in high demand. In this research, a highly efficient organic photovoltaic cell was successfully demonstrated by the electrospray deposition method using a non‐halogenated solvent, o‐xylene. An addition of acetonitrile and 1,8‐diiodooctane drastically reduced domain size of the organic active layer, resulting in improved device performance. In addition, the photoconversion efficiency was continuously increased with increasing the solvent evaporation time of a droplet deposited on a substrate, and the highest photoconversion efficiency of 5.6% was achieved by optimizing the solvent evaporation time.Current‐density–voltage characteristics under irradiation with AM 1.5 light and corresponding AFM images of the active layers electrosprayed with and without the addition of 1,8‐diiodooctane in o‐xylene and acetonitrile.

Using PDMS coated TFC-RO membranes for CO2/N2 gas separation: Experimental study, modeling and optimization

Thin film composite (TFC) reverse osmosis (RO) membranes are semipermeable membranes that are utilized in water purification or water desalination systems. Discarding these membranes after end-of-life leads to environmental problems. Reusing old TFC-RO membranes is one way to solve this problem. For this reason, in this study, used TFC-RO membranes were coated with polydimethylsiloxane (PDMS) for CO2/N2 gas separation application. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was utilized to confirm the crosslinking of coated PDMS. The morphology of PDMS/TFC-RO membranes was characterized using scanning electron microscopy (SEM). The parameters that can affect performance of prepared membranes (N2 permeance and CO2/N2 selectivity) are concentration of PDMS solution, coating time, solvent evaporation time and curing temperature and time. Given that the used membranes don't have uniform surfaces, the first step of this study was to investigate the effect of the above mentioned factors on virgin membranes using fractional factorial design (FFD) of experiments. The results obtained showed that PDMS concentration is the most significant factor that has a negative effect on N2 permeance and positive effect on CO2/N2 selectivity. The reported CO2/N2 selectivity of PDMS membranes was 11–12, but this selectivity for prepared PDMS/TFC-RO membranes was in the range of 6.7–22.5. After determining optimum conditions, the gas separation performance of PDMS coated used TFC-RO membrane under these conditions was finally determined. The results showed that the used membranes had a better performance than virgin membranes.

Gaining Further Insight into the Solvent Additive-Driven Crystallization of Bulk-Heterojunction Solar Cells by in Situ X-ray Scattering and Optical Reflectometry

The use of solvent additives has become a successful strategy to control the structural evolution upon film formation in bulk-heterojunction (BHJ) solar cells. Nonetheless, a complete understanding of the additive’s role in the phase separation mechanisms and organization of donor and acceptor materials in BHJs is still lacking. In this work we gain further insight about the specific role that a widely used additive, 1,8-octanedithiol (ODT), has in the crystallization of both PCPDTBT and PC71BM, directly after wet film deposition using blade-coating. By in situ X-ray scattering and optical reflectometry, we correlate the additive-driven crystallization with the evolution of film composition from the earliest time of solvent evaporation. It is shown that ODT influences the evolution of both PCPDTBT and PC71BM. ODT leads to prolonged crystallization time during the ODT-drying dominated period corresponding to an overall solvent content (x) of 75 wt % > x > 15 wt % and delays the onset of PC71BM aggregation ...

Molecular ordering of spin-coated and electrosprayed P3HT:PCBM thin films and their applications to photovoltaic cell

Poly(3-hexylthiophene-2,5-diyl) (P3HT) is one of the most popular donor polymers for organic photovoltaic cells; however, annealing-induced molecular ordering is necessary for realizing high photoconversion efficiency. In this study, the ratio of ordered-disordered P3HT Raman signals was calculated as the crystallinity parameter, which can be evaluated as the molecular ordering of P3HT. In the case of spin-coated devices, the crystallinity parameter increases with increasing annealing temperature, and this agrees with the photovoltaic performance. Furthermore, the direct molecular ordering of P3HT during electrospray deposition is reported, detailing the relation between the solvent evaporation time and the crystallinity of P3HT, and is evaluated by Raman spectroscopy and grazing incidence X-ray diffraction. To observe the solvent evaporation phenomena of the electropsray process, in situ measurement of solvent evaporation time was also successfully realized for the first time by placing a CCD camera below the substrate in electrospray deposition. The solvent evaporation time was controlled from 0.036 to 2.8s by changing the applied voltage and solvent. By investigating the relationship between the solvent evaporation time and the molecular ordering of P3HT, the long solvent evaporation time caused the high crystallinity of P3HT. In addition, the population of P3HT crystallinity with an edge-on orientation also increased with increasing solvent evaporation time by evaluating the grazing incidence X-ray diffraction pattern, in good agreement with the estimated crystallinity from Raman spectroscopy. Finally, a photoconversion efficiency of 2.0% was achieved by electrospray deposition without post thermal annealing.