Dimethylacetamide Solution Research Articles

Composite Films Based on Methyl Cellulose Mixtures with Poly(urethane-imide) Obtained from Their Solutions in Dimethylacetamide

Composite Films Based on Methyl Cellulose Mixtures with Poly(urethane-imide) Obtained from Their Solutions in Dimethylacetamide

Composite Films Based on Methyl Cellulose Mixtures with Poly(urethane-imide) Obtained from Their Solutions in Dimethylacetamide

Composite films of methyl cellulose and poly(urethane-imide) are obtained. At the poly(urethane-imide) content in the films above 50% phase separation of the polymers is observed. Using the methods of dynamic mechanical analysis and X-ray diffraction the structural organization of the films is studied, the temperatures of relaxation transitions are determined, and the mechanical characteristics of the composite films are investigated.

Preparation and Characterization of Microporous Cellulose Membranes as Potential Pathogen Filters

Growth and development in the textile and fashion industry have resulted in the generation of large amounts of industrial pre-consumer textile wastes. It is estimated that 10 to 20% of textile fabrics are wasted during garment manufacturing, with most of the wastes being burned or landfilled. Reusing pre-consumer fabric wastes is therefore considered a viable approach to alleviate environmental impacts associated with their disposal. To achieve a higher porosity membrane, pre-consumer cotton fabrics were partially dissolved in a solution of dimethyl acetamide (DMAc) and lithium chloride (LiCl), and the resulting fibre suspension was utilized to prepare a microporous cellulose membrane (MCM) through a vacuum filtration method. The suspension comprised a mixture of partially and completely dissolved fibres, which provided the required morphological and structural integrity to the fibrous membranes. The membranes’ chemical structure, fibre size, and morphology were characterized based on Fourier transform infrared spectroscopy (FT-IR), light microscope, and field emission scanning electron microscopy (FE-SEM), respectively. The filtration efficiency of the microporous cellulose membranes was evaluated against 500 ppm sodium chloride (NaCl) solutions. The results showed that the filtration efficiency of the membranes ranged between 31.82 and 59.85% for cellulose membranes with 60.2% porosity, suggesting that the membranes could be applied as filters against pathogens upon further improvement.

One-step post-treatment boosts thermoelectric properties of PEDOT:PSS flexible thin films

• High power factor of 64.4 µW m −1 K −2 is achieved in PEDOT:PSS films at 360 K. • 80 vol.% DMAC solution boosts the electrical conductivity from 5 to 964 S cm −1 . • 0.5 mol L −1 LAA improves the Seebeck coefficient from 18.7 to 25 µV K −1 . • Mott variable range hopping model explains the thermoelectric transport behavior. Developing high-performance poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) significantly widens the practical applications of flexible organic thermoelectric devices, while the water-based co-solvent dopants and/or post-treatments are still rarely studied so far. Here, we develop a one-step post-treatment to improve the power factor of PEDOT:PSS films by using a water-based solution, which is composed of co-solvent (polar solvent dimethylacetamide (DMAC) and deionized water) and organic reducing agent L-ascorbic acid (LAA). The 80 vol.% DMAC solution significantly boosts the room-temperature electrical conductivity of the films from 5 to 964 S cm −1 , while the Seebeck coefficient can be further enhanced from 18.7 to 25 µV K −1 by treating with 0.5 mol L −1 LAA, contributing to a significantly improved power factor of 55.3 µW m −1 K −2 . The boosted electrical conductivity is ascribed to the separated PEDOT and PSS phases triggered by the high dielectric constant and polarity of DMAC; while the improved Seebeck coefficient is attributed to the reduced oxidation degree of PEDOT from the reducing agent LAA, both confirmed by the comprehensive structural and morphological characterizations. Furthermore, a maximum power factor of 64.4 µW m −1 K −2 can be achieved at 360 K and the observed temperature-dependent electrical transport behavior can be well explained by the Mott variable range hopping model. Besides, a flexible thermoelectric device, assembled by the as-fabricated PEDOT:PSS films, exhibits a maximum output power of ∼23 nW at a temperature difference of 25 K, indicating the potential for applying to low-grade wearable electronics.

The Use of Pectins As Part of a Cryoprotective Solution For Long-term Storage of Human Platelet Concentrates

BACKGROUND: Pectins have unique properties and great potential to become an indispensable component of cryoprotective environment for platelet freezing. OBJECTIVE: To investigate the possibility of including pectins (apple pectin AU-701, tanacetan) into the composition of a cryoprotective solution for platelets during low-temperature storage. MATERIALS AND METHODS: Samples of platelet concentrates (PC) were frozen under the protection of complex solutions and stored in an electric freezer at -80 °C for 1 and 6 months. RESULT: The study showed that of the basic cryoprotectants, the best effect in the preservation of PC was with dimethylacetamide (DMAC). The use of pectins as an additive to the base solution of DMAC statistically improves the preservation of PC after exposure to low temperatures (-80 ° C) for 30 and 180 days. CONCLUSIONS: We conclude that DMAC is more promising as a basis for the development of a new combined cryoprotectant for PC freezing. Moreover, the chemical structure of pectin determines the level of its cryoprotective action in relation to the preservation of PC.

Evaluation of the quality of native and cryopreserved semen of birds of breeds brama light and brama fawn and their chimeras

Due to the significant decline in the diversity of bird breeds and populations, there is a need to preserve germ cells of rare breeds and unique organisms, such as chimeras. The main method for preserving the gene pool in birds is the method of semen cryopreservation, which is used in many countries of the world in the form of creating cryobanks. Sperm from the birds of the breeds Brama light and Brama fawn and their chimeras were obtained by abdominal massage. Cryopreservation of the semen was carried out in small granules with the addition of a 6% solution of dimethylacetamide. The granules were thawed on a heated metal plate at 60°C. The ejaculate volume, sperm activity and its concentration in the studied breeds and their chimeras did not differ statistically. The maximum activity of the frozen-thawed semen was observed in the semen of the Brahma fawn breed (40.0%), and the minimum activity in the Brahma light breed was 30%, while in chimeras the semen activity occupied an intermediate position and amounted to 35%. Thus, frozen-thawed spermatozoa of bird chimeras are viable, as well as native semen.

Mathematical modeling of the properties of thermal insulation materials based on hollow ceramic microspheres and phenylon

In this work, the creation of heat-insulating materials that are still operable at temperatures up to + 400 °C and have increased physical and mechanical characteristics was studied. This aim was achieved by using a heat-resistant polymer binder phenylon (an aromatic polyamide) and hollow ceramic microspheres, that were used as a filler. Phenylon was produced by OJSC «Polimersintez» in Vladimir. Hollow ceramic microspheres are the floating fractions of flue emissions from solid-fuel thermal power plants. Thermal insulation materials were made by mixing hollow ceramic microspheres with a phenylon solution in dimethylacetamide to the state of «wet sand». Then, the obtained substance was molded the solvent residues were removed. Furthermore, the main properties of the obtained materials were also studied. It was established that the thermal insulation material is characterized by high strength characteristics, has significant resistance to impact loads and is operable at temperatures up to 400 °C The developed thermal insulation materials are intended to be used in the construction of objects operating under the conditions of cyclic exposure to high temperatures (for example, power plants) and in the construction of objects operating under the conditions of cyclic exposure to high temperatures (for example, power facilities).

A Wet-Spinning Process for Producing Carbon Nanotube/Polyvinylidene Fluoride Fibers Having Highly Consistent Electrical and Mechanical Properties.

Studies of polymer/carbon nanotube (CNT) fibers typically focus on optimizing the overall properties, and the effects of structural variation on these properties are ignored. Thus, we investigated the longitudinal variation in the properties of CNT/polyvinylidene fluoride (CNT/PVDF) fibers prepared by wet spinning a solution of multi-walled nanotubes, PVDF, and dimethylacetamide. To this end, materials for the CNT/PVDF fiber were selected, and a dope solution was prepared using MWNT, PVDF, and dimethylacetamide (DMAc). To consider the process parameters that would affect the performance of the CNT/PVDF fiber during the wet-spinning process using the dope solution, the initial conditions for wet spinning were selected, including bath concentration, bath temperature, drying temperature, and elongation, and the CNT/PVDF fiber was spun under the corresponding conditions. Additionally, three performance stabilization processes were proposed to improve the initial conditions for wet spinning and manufacturing the fiber. Lastly, to confirm the reliability of the CNT/PVDF fiber in all sections, tensile strength, electrical conductivity, and cross-sectional images were analyzed for the 30 m, 60 m, and 90 m sections of the fiber, and the reliability of the wet-spinning process was verified.

Synthesis of a hydroxylamino-modified silicone oil for use in a polyacrylonitrile oil emulsion in carbon fiber production

In order to prepare a stable oil emulsion suitable for polyacrylonitrile (PAN) in carbon fiber production, a hydroxylamino-modified silicone oil (HA-PDMS) was synthesized by a three-step procedure and mixed with a commercial epoxy-modified silicone oil in water to prepare an oil emulsion of PAN (P-OE) in carbon fiber preparation. The structure of the intermediate products and P-OE were analyzed by FT-IR and 1H-NMR. The major properties of P-OE were investigated by a laser particle size analyzer, thermogravimetric analyzer and surface tension instrument and compared with those of the commercial one used in Japan (J-OE). The polyacrylonitrile solution in dimethyl acetamide was drawn by wet spinning and impregnated in P-OE and J-OE to obtain P-PAN and J-PAN, respectively, which were carbonized to obtain carbon fibers P-CF and J-CF. The Roder friction coefficient, hairiness and tensile strength of P-PAN, J-PAN, P-CF and J-CF were tested to compare the performance of the two kinds of oil emulsions for use in PAN-based carbon fiber production. Results show that the tensile strength of P-PAN is higher than that of J-PAN. Compared with J-CF, the tensile strength and tensile modulus of P-CF are higher and the hairiness is greatly reduced. P-OE is superior to J-OE for the use as an oil emulsion of PAN in production of PAN-based carbon fibers.

Prototype Profile of Supercapactors with Activated Carbon/Fe3O4 Electrodes Natural Materials and Celgard Li-Ion Battery Separators

The electrode composition material in the supercapacitor affects the storage performance of the supercapacitor. In this study, the electrodes were made from coconut shell activated carbon and Fe3O4 from iron sand. To be used as electrodes, the two materials are mixed with PVDF and a solution of Dimethylacetamide at a temperature of 70°C; then, a coating process is carried out by layering the electrode material onto aluminium foil to obtain an electrode sheet. The coin cell assembling process was then carried out by arranging the electrode sheets and the Celgard Li-ion battery separator in the glove box and then tested for charge/discharge with a current density of 5-81 mA/g and cycle stability at a current of 20 mA/g. The study results show that the activated carbon/5 wt% Fe3O4 supercapacitor has the best capacitance value for charging at 8.03 F/g and discharging at 8.55 F/g at a current density of 5 mA/g. The activated carbon/5 wt% Fe3O4 supercapacitor has cycle stability of up to 200 cycles and can withstand up to 95% with a capacitance of 6.6 F/g.

Molecular Rotors with Aggregation-Induced Emission (AIE) as Fluorescent Probes for the Control of Polyurethane Synthesis

In this work, the use of fluorescent molecular rotors such as 9-(2,2-dicyanovinyl)julolidine (DCVJ) and 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl) phenyl)amino)phenyl)fumaronitrile (TPETPAFN) was proposed for the real-time monitoring of polyurethane (PU) formation in a solution of dimethylacetamide starting with 4,4′-methylenediphenyl diisocyanate (MDI) and different polyethylene glycols (PEG400 and PEG600) as diols. Notably, relative viscosity variations were compared with fluorescence changes, recorded as a function of the polymerization progress. The agreement between these two parameters suggested the innovative use of a low-cost fluorescence detection system based on a LED/photodiode assembly directly mountable on the reaction apparatus. The general validity of the proposed experiments enabled the monitoring of polyurethane polymerization and suggested its effective applications to a variety of industrial polymers, showing viscosity enhancement during polymerization.

Polyacrylonitrile (PAN)/TiO2 mixed matrix membrane synthesis by thermally induced self-crosslinking for thermal and organic-solvent resistant filtration

A polyacrylonitrile (PAN)@TiO2 mixed matrix membrane is first fabricated in-situ by the nonsolvent induced phase separation (NIPS) method. Most of the in-situ generated TiO2 nanoparticles are extracted close to the upper layer of the membrane due to their high hydrophilicity, and they strongly interact with the PAN molecules; this enables the resistance of the excessive heat-induced motion of the PAN molecules and prevents structure shrinkage of the pore structures. The thoroughly self-crosslinked PAN@TiO2 membrane (TPAN@TiO2) has a strong resistance against solvents, such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO). All three highly polar organic solvents exhibit 24 h stable permeance at 100 °C with the new membrane. More than 99.5% of Rose Bengal and 88.5% of rhodamine B are rejected from a solution of DMAc. Considering its superior performance, the novel membrane shows promise for application in future desalination processes.

Composition and Structure of Hydrates Formed in Aqueous Dimethylacetamide Solutions

Hydration in aqueous solutions of dimethylacetamide was studied by IR spectroscopy and quantum chemistry; the concentration and structural zones were determined. An analysis of the concentration dependences of IR absorption of these solutions at different frequencies showed that heteroassociates with stoichiometric ratios of components of 2 : 1, 1 : 1, 1 : 2, and 1 : 4 formed in them in sequence. The composition, structure, formation energy, and relative stability of the heteroassociates were determined from the results of DFT calculations for 19 hydrates. The stability of dimethylacetamide hydrates was shown to increase with the relative content of water molecules in them.

Fabrication of polyimide films with imaging quality using a spin-coating method for potential optical applications

Abstract Optical polyimide (PI) films were prepared by spin-coating from nearly non-volatile dimethylacetamide (DMAc) solutions. The uniformity of film thickness met the requirements of diffraction imaging quality. The results show that the final rotating speed ω, dynamic viscosity η, and initial polymer solid concentration c are the main factors affecting the film thickness T, and an empirical relationship which describes the film thickness as a function of the measured parameters was established to be T ∝ c 3.473 , η 0.586 , ω − 0.811 . $T \propto {c^{3.473}},{\rm{ }}{\eta ^{0.586}},{\rm{ }}{\omega ^{ - 0.811}}.$ Moreover, the viscosity dependence on concentration is system specific. Unlike traditional photoresist, the thickness uniformity of the PI film is determined by both spinning and precure process, which is intensively discussed in the present work. Uniform, 22-μm thick, PI films with transmitted wavefronts peak to valley (PV) ≤ 1/5 λ and root mean square (RMS) ≤ 1/50 λ were prepared under the optimum process: spin speed 900 rpm, initial fluid viscosity 10,500 cp, final spin time 120 s, precure temperature 70°C, spin process repeated 3 times. The results will find use in the production of optical quality membrane for ultra-lightweight optics or other applications.

New scents from bio-renewable cis-jasmone by aerobic palladium catalyzed oxidations

The palladium catalyzed oxidation is a versatile method for upgrading of cis-jasmone, a main aroma constituent of jasmine essential oil. Although both olefinic bonds in cis-jasmone are sterically hindered, the substrate has demonstrated a remarkable reactivity in Wacker type oxidations. Depending on the catalyst and the solvent, reactions can be directed to either allylic oxidation or ketone products. The oxidation in acetic acid solutions with a chloride-free Pd(OAc)2/p-benzoquinone catalyst gave with high selectivity an allylic acetate. An efficient oxygen-couple catalytic turnover can be achieved either under atmospheric pressure with catalytic amounts of Cu(OAc)2 to promote the regeneration of p-benzoquinone or at 5–10 at m of oxygen in the absence of any auxiliary co-catalyst. Alternatively, cis-jasmone can be oxidized to ketone products in aqueous dimethylacetamide solutions using molecular oxygen as a final oxidant and PdCl2 as a sole catalyst. Poly-functionalized jasmonoids obtained are potentially useful as components of perfumes and cosmetics.

Fabrication of high flux and fouling resistant membrane: A unique hydrophilic blend of polyvinylidene fluoride/polyethylene glycol/polymethyl methacrylate

To overcome the fouling issue of membrane, hydrophilic membrane fabrication is a rich research domain. In this study, hydrophilic membrane was fabricated by incorporating the hydrophilic polymer into dope solution. Polymethyl methacrylate (PMMA) was blended with polyvinylidene fluoride (PVDF) (12%), polyethylene glycol (PEG) (2%), and N,N dimethyl acetamide (DMAc) solution and membranes were prepared by non-solvent induced phase separation process (NIPS). The synthesized membranes were characterized for their surface and cross-sectional morphology, crystallinity, chemical composition, hydrophilicity, pore size, porosity, permeability, pollutant retention, and fouling resistance. The addition of only PEG to PVDF and PMMA to PVDF increased the porosity, pore size and hydrophilicity of the membrane. Whereas, a combination of both PEG (2%) and PMMA (1%) into PVDF further increased the hydrophilicity (contact angle 60°) and porosity (90%) of the membrane. The maximum pure water flux (PWF) (565 LMH) was also recorded with PVDF-PEG-PMMA membrane without compromising the humic acid (HA) retention rate (80%). Moreover, flux recovery ratio of PVDF-PEG-PMMA membrane was more than 80% with hydraulic flushing. The combination of PEG and PMMA proved to be very effective for improving the properties of PVDF membrane resulting in better flux and antifouling potential of the membrane.

Sulfonated PBI Gel Membranes for Redox Flow Batteries

Sulfonated polybenzimidazole (s-PBI) gel membranes were prepared and shown to have a high stability in concentrated sulfuric acid and strongly oxidizing vanadium (V) solutions. These membranes were considered candidates for use in vanadium redox flow batteries, and compared to the commonly used “conventionally imbibed” meta-polybenzimidazole (m-PBI) membranes cast from N,N’-dimethylacetamide (DMAc) solutions. The s-PBI membranes exhibited high conductivities (up to ∼240 mS cm−1) and low performance degradation during in-cell testing.

Novel meta- and AB-Polybenzimidazole/Zinc oxide polymer hybrid nanomaterials for photocatalytic degradation of organic dyes

New nanocomposites of m-PBI/ZnO and AB-PBI/ZnO – powders and films, containing 2.5 wt% and 5 wt% ZnO, were prepared using two different approaches: mixing commercial ZnO nanoparticles with dimethylacetamide solution of m-PBI and in situ synthesis of ZnO in alkali-ethanol AB-PBI solution. The photocatalytic activity of the materials prepared was tested for photodegradation under UV-light of model organic dyes pollutants, in aqueous media. The powder catalysts exhibit higher photocatalytic efficiency towards degradation of all three tested dyes, compared to the films. The materials containing 2.5 wt% ZnO are usually more efficient than these with 5 wt% ZnO. The highest degree of degradation (97%) was achieved for Malachite Green dye, using m-PBI/2.5 wt% ZnO powder.

Spin coated chitin films for biosensors and its analysis are dependent on chitin-surface interactions

Chitin, abundant in nature, is a renewable resource with many possible applications in bioengineering. Biosensors, capable of label-free and in-line evaluation, play an important role in the investigation of chitin synthesis, degradation and interaction with other materials. This work presents a comparative study of the usefulness of a chitin surface preparation, either on gold (Au) or on polystyrene (PS). In both cases the most common method to dissolve chitin was used, followed by a simple spin-coating procedure. Multi-parametric surface plasmon resonance (MP-SPR), modeling of the optical properties of the chitin layers, scanning electron microscopy, and contact angle goniometry were used to confirm: the thickness of the layers in air and buffer, the refractive indices of the chitin layers in air and buffer, the hydrophobicity, the binding properties of the chitin binding domain (CBD) of Bacillus circulans, and the split-intein capture process. Binding of the CBD differed between chitin on Au versus chitin on PS in terms of binding strength and binding specificity due to a less homogenous structured chitin-surface on Au in comparison to chitin on PS, despite a similar thickness of both chitin layers in air and after running buffer over the surfaces. The use of the simple method to reproduce chitin films on a thin polystyrene layer to study chitin as a biosensor and for chitin binding studies was obvious from the SPR studies and the binding studies of CBD as moiety of chitinases or as protein fusion partner. In conclusion, stable chitin layers for SPR studies can be made from chitin in a solution of dimethylacetamide (DMA) and lithium chloride (LiCl) followed by spin-coating if the gold surface is protected with PS.

Fabrication of novel magnetic zinc oxide cellulose acetate hybrid nano-fiber to be utilized for phenol decontamination

An innovative magnetic nano-fiber composite was prepared via hybridization nano-magnetite zinc oxide and cellulose acetate (CA) using electrospinning technique. The affinity of synthesized composite nano-fiber for phenol adsorption from aqueous solution was monitored. Different parameters that effected on the fabrication of pure CA nano-fiber were optimized. The most proper fabricated CA nano-fiberr was achieved using 10% CA that was dissolved at acetone and dimethylacetamide (DMAc) solution with mixing ratio 2:1 the electrospinning applied voltage was 20 KV and the appropriate separation distance was 25 cm using 0.5 ml/h flow rate. Different weights of magnetic zinc oxide were immobilized onto the most proper fabricated CA nano-fiber (10% CA) to fabricate novel ZnO magnetic CA composite nanofiber. The various fabricated CA based nano-fibers either after and before magnetic ZnO immobilization were characterized using SEM, XRD and FTIR. The phenol sorption affinities of the various fabricated CA nano-fibers were tested using synthetic polluted wastewater in batch manner. It was recorded that magnetite ZnOCA hybrid nanofiber with 0.1% magnetic zinc oxide immobilization represents the most efficient fabricated nanofiber compared with other studied fabricated CA based nano-fiber. This novel composite nano-fiber has ability to adsorb 64% of phenol within 2 h. The various parameters affecting the phenol sorption process onto this novel fabricated composite were optimized. It was evident that the increment at both the solution pH and temperature has negative impact on the phenol sorption process onto the novel fabricated magnetic ZnOCA composite nano-fiber.