Mixture Of Dimethylformamide Research Articles

Fabrication of Piezoelectric Electrospun Termite Nest-like 3D Scaffolds for Tissue Engineering.

A high piezoelectric coefficient polymer and biomaterial for bone tissue engineering— poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)—has been successfully fabricated into 3D scaffolds using the wet electrospinning method. Three-dimensional (3D) scaffolds have significant advantages for tissue engineering applications. Electrospinning is an advanced method and can fabricate 3D scaffolds. However, it has some limitations and is difficult to fabricate nanofibers into 3D shapes because of the low controllability of porosity and internal pore shape. The PVDF-HFP powders were dissolved in a mixture of acetone and dimethylformamide with a ratio of 1:1 at various concentrations of 10, 13, 15, 17, and 20 wt%. However, only the solutions at 15 and 17 wt% with optimized electrospinning parameters can be fabricated into biomimetic 3D shapes. The produced PVDF-HFP 3D scaffolds are in the cm size range and mimic the structure of the natural nests of termites of the genus Apicotermes. In addition, the 3D nanofiber-based structure can also generate more electrical signals than the conventional 2D ones, as the third dimension provides more compression. The cell interaction with the 3D nanofibers scaffold was investigated. The in vitro results demonstrated that the NIH 3T3 cells could attach and migrate in the 3D structures. While conventional electrospinning yields 2D (flat) structures, our bio-inspired electrospun termite nest-like 3D scaffolds are better suited for tissue engineering applications since they can potentially mimic native tissues as they have biomimetic structure, piezoelectric, and biological properties.

Nanoporous Block Copolymer Membranes with Enhanced Solvent Resistance Via UV-Mediated Cross-Linking Strategies.

In this work, a block copolymer (BCP) consisting of poly((butyl methacrylate-co-benzophenone methacrylate-co-methyl methacrylate)-block-(2-hydroxyethyl methacrylate)) (P(BMA-co-BPMA-co-MMA)-b-P(HEMA)) is prepared by a two-step atom-transfer radical polymerization (ATRP) procedure. BCP membranes are fabricated applying the self-assembly and nonsolvent induced phase separation (SNIPS) process from a ternary solvent mixture of tetrahydrofuran (THF), 1,4-dioxane, and dimethylformamide (DMF). The presence of a porous top layer of the integral asymmetric membrane featuring pores of about 30nm is confirmed via scanning electron microscopy (SEM). UV-mediated cross-linking protocols for the nanoporous membrane are adjusted to maintain the open and isoporous top layer. The swelling capability of the noncross-linked and cross-linked BCP membranes is investigated in water, water/ethanol mixture (1:1), and pure ethanol using atomic force microscopy, proving a stabilizing effect of the UV cross-linking on the porous structures. Finally, the influence of the herein described cross-linking protocols on water-flux measurements for the obtained membranes is explored. As a result, an increased swelling resistance for all tested solvents is found, leading to an increased water flux compared to the pristine membrane. The herein established UV-mediated cross-linking protocol is expected to pave the way to a new generation of porous and stabilized membranes within the fields of separation technologies.

Two Unexpected Temperature-Induced Supermolecular Isomers from Multi-Topic Carboxylic Acid: Hydrogen Bonding Layer or Helix Tube.

Under ambient conditions or 160 °C, two supramolecular isomers, namely [(H4PTTA)(H2O)2(DMF)] and [(H4PTTA)(H2O)3]··Guest (1-L and 1-H, H4PTTA = N-phenyl-N′-phenyl bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxdiimide tetra-carboxylic acid, Guest = DMF and H2O), were obtained through the reaction of H4PTTA in a mixture of H2O and dimethylformamide. The single crystal structures reveal the temperature-dependent supramolecular isomerism derived from the torsion of semi-rigid of H4PTTA. The 1-L prepared at room temperature is a hydrogen bond based achiral layer, while the hydrothermal synthesized 1-H is isomer resulted in an H-bond-based chiral tubes-packed supramolecular framework.

Symmetry Breaking in an Excited Quadrupolar Acridine-Dione Derivative Driven by Hydrogen Bonding.

An acridine-dione derivative (3,3,11,11-tetramethyl-8,16-diphenyl-3,4,8,10,11,12,13,16-octahydroacridino[4,3-c]acridine-1.9(2H,5H)dion) with quadrupolar motif has been synthesized and its stationary and transient spectra have been measured. Stationary absorption and fluorescence spectra as well as nonstationary spectra show no signs of symmetry breaking (SB) in aprotic solvents, even of high polarity. The specific features of SB are revealed in alcohol solvents through a considerable red shift of stationary fluorescence spectra and the appearance of a new excited state absorption band in transient absorption spectra. SB is due to the formation of asymmetric strong hydrogen bonds, mainly on one side of the molecule. An unexpected regularity of symmetry breaking is found in mixtures of aprotic dimethylformamide and protic methanol, where methanol acts as a fluorescence quencher. It is revealed that there is no quenching as long as the methanol concentration is less than the critical value of 9 M. This leads to the conclusion that SB in such mixtures is possible only if the concentration of the protic solvent exceeds a certain threshold value.

Polymer Chromophore–Catalyst Assembly for Photocatalytic CO2 Reduction

A polystyrene-based chromophore–catalyst assembly (PS-RuC/RuCat) was synthesized and applied for photocatalytic CO2 reduction in an organic solution in the presence of a sacrificial donor. The polymer assembly contains Ru(bpy)32+ (RuC, bpy = 2,2′-bipyridine) as the chromophore and a derivative of [Ru(tpy)(6-mbpy)(CH3CN)]2+ (RuCat, tpy = 4′-phenyl-2,2′:6′,2″-terpyridine and 6-mbpy = 6-methyl-2,2′-dipyridyl) as the CO2 reduction catalyst. The photophysical and electrochemical properties of the polymer assembly were investigated. Picosecond transient absorption and time-resolved emission reveal that the RuC chromophores are quenched by energy transfer to the RuCat units in the polymer assembly. Cyclic voltammetry shows that PS-RuC/RuCat effects electrocatalytic reduction of CO2 with an onset of approximately −1.25 V versus Ag/AgCl. Photocatalytic studies were conducted separately for the PS-RuC/RuCat polymer assembly and a mixture of monomers RuC and RuCat in a mixture of dimethylformamide and triethanolamine with 1-benzyl-1,4-dihydronicotinamide as a sacrificial reductant. The primary CO2 reduction products CO and H2 were detected in both photocatalytic systems. Formic acid was detected at low levels by nuclear magnetic resonance and is a very minor product. The polymer assembly system shows a lower photocatalytic CO2 reduction quantum yield (6.7%) but exhibits improved stability compared with a mixed molecular chromophore/catalyst system.

Influence of Molecular Weight Distribution on the Thermoresponsive Transition of Poly(N-isopropylacrylamide).

A series of poly(N-isopropylacrylamide) (PNIPAm) homopolymers with narrow molecular weight distributions (MWDs) is prepared via photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. The thermal transition temperature of these polymer samples is analyzed via turbidity measurements in water/N,N'-dimethylformamide mixtures, which show that the cloud point temperatures are inversely proportional to the weight average molecular weight (Mw ). Binary mixtures of the narrowly distributed PNIPAm samples are also prepared and the statistical parameters for the MWDs of these blends are determined. Very interestingly, for binary blends of the PNIPAm samples, the thermoresponsive transition is not only dependent on the Mw , which has been shown previously, but also on higher order statistical parameters of the MWDs. Specifically, at very high values of skewness and kurtosis, the polymer blends deviate from a single sharp thermoresponsive transition toward a broader thermal response, and eventually to a regime of two more distinct transitions. This work highlights the importance of in-depth characterization of polymer MWDs for thermoresponsive polymers.

Ultrahigh Hydrogen Uptake in an Interpenetrated Zn 4 O-Based Metal–Organic Framework

As a highly promising candidate for hydrogen storage, crucial to vehicles powered by fuel cells, metal–organic frameworks (MOFs) have attracted the attention of chemists in recent decades. H2 uptak...

A supertetrahedral T2 [Mn4Ce6] cluster showing second-harmonic generation response

The self-assembly reaction of MnCl2·4H2O, Ce(acac)3·xH2O (acac = deprotonated acetylacetone), and acenaphthenequinone dioxime (acndH2) in a mixture of methanol and dimethyl formamide (DMF) has led to a [MnIII4CeIV6] cluster MnIII4CeIV6(μ-O)8(acnd)4(OAc)4(acac)4(CH3O)4(DMF)4 (1) with a supertehedral T2 metal topology. Owing to the helical alignment of the supertetrahedral clusters, compound 1 shows a weak second-harmonic generation (SHG) response. Magnetic studies reveal very weak antiferromagnetic couplings between the paramagnetic MnIII ions.

In-situ modification of low molar ratio urea–formaldehyde resins with cellulose nanofibrils for plywood

This study describes the in-situ modification of low molar ratio urea–formaldehyde (UF) resins with cellulose nanofibrils (CNFs) to improve the poor performance of resins synthesized with different methods (Synth 1 and Synth 2) when adding second urea. UF resins were in-situ modified with CNFs dissolved in a mixture of dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) during the alkaline reaction step. Results showed that CNF addition enhanced the resin properties, such as shorter gelation time, faster curing rates at low activation energy, higher tensile shear strength (TSS), and lower formaldehyde emission (FE), compared to those of neat resins. The dry and wet TSS values of plywood bonded with UF resins modified with 3% CNFs synthesized using Synth 2 increased by 30% and 42%, respectively, and the FE value was decreased by 22% and 42%, respectively. These results reveal that in-situ modified UF resins with CNFs showed better performance than neat UF resins and that Synth 2 was more favorable than Synth 1.

Highly mesoporous and chemically bonded Fe3O4/N-doped carbon nanocomposite with an outstanding cycling life as lithium-ion-battery anode

Owing to high theoretical capacity (926 mAh g−1), Fe3O4 has achieved much focus as a prospective anode material for lithium-ion batteries (LIBs). A one-step vapor-pressured induced approach considering the synthesis of chemically bonded Fe3O4/N-doped carbon nanocomposites (Fe3O4/NC) via Fe-O-C and Fe-N-C, together with the encapsulation of Fe3O4 nanoparticles (∼80 nm) into highly mesoporous N-doped carbon matrix via pyrolyzing the mixture of iron oxalate and dimethylformamide in a sealed vessel, does not exist at present. As LIB anode, the Fe3O4/NC presents a high capacity of 1250.2 mAh g−1 at 0.1 A g−1, an outstanding cyclability with a capacity of 600.1 mAh g−1 after 4000 cycles at 5 A g−1, and a high rate capability (244.8 mAh g−1 at 20 A g−1). Such excellent performances can be ascribed to its unique structure that Fe3O4 nanoparticles tightly encapsulated into highly mesoporous N-doped carbon matrix can increase active sites, electrical conductivity, and cyclability.

Effect of solvents and annealing treatment on the properties of the methylammonium lead tribromide perovskite thin films

Solution-processed hybrid organic–inorganic perovskites from organoammonium halide and lead halide precursors form effective active layers for optoelectronics devices. The solvent plays a decisive factor on the preparation of active layer for perovskite application. In this report, the properties of methylammonium lead tribromide (MAPbBr3) thin films were studied using various solvents. The solvents used were dimethylformamide (DMF), dimethyl sulfoxide (DMSO), a mixture of DMF + IPA (Isopropanol). The photoluminescence and absorption spectra show a good solubility of the perovskite content in the mixed solvent than that with DMF or DMSO which is attributed to the good crystallization of content in the film. Furthermore, the effect of annealing treatment on the structural and optical properties of MAPbBr3 thin films prepared with DMF + IPA was investigated. The MAPbB3 film annealed at 100 °C has considerably improved the dissociation of the charges resulting from the good interaction of the solvent with the perovskite material and the good perovskite film quality.

Production of Nanofiber Materials Based on Macromolecular Hyaluronic Acid by Electrospinning

Hyaluronic acid-based nanofiber scaffolds imitating the natural extracellular matrix, which is promising for use in tissue engineering, have been prepared by electrospinning. Hyaluronic acid is part of many organs and tissues; it is a biologically active component capable of being involved in cell proliferation and migration. The high viscosity of solutions of the macromolecular biopolymer significantly complicates the preparation of nanofiber scaffolds based on it. Rheological studies have made it possible to determine the solvent composition that contributes to a decrease in the viscosity of the spinning solution. The highest Newtonian viscosity of a 1% hyaluronic acid solution in water is 25 Pa s; in the case of using a mixture of ammonia hydrate (10%) and dimethylformamide at a ratio of 2 : 1, this parameter decreases to 1.147 Pa s. The use of a special spinning cell with a small-diameter nozzle and a high pressure (up to 10 atm) has provided the formation of hyaluronic acid-based nanofibers with a diameter of 100–300 nm.

Solvent effects on the structural and catalytic properties of Pt nano- and microstructures synthesised in solvothermal system

Platinum (Pt) nano- and microstructures were synthesised in different types of solvent (e.g. water (H2O), dimethylformamide (DMF), monoethanolamine (MEA) and a mixture of H2O and DMF) by using solvothermal technique. Spherical particles of diameter ranging from 80 nm to 230 nm were formed when prepared in H2O, whereas particles with irregular shapes were produced from the H2O/DMF media. Particles with flower-like structures of diameter ranging from 140 nm to 200 nm were produced by using DMF solvent, while cubic microstructures with sizes of about 0.7 μm−1.0 μm were formed in the MEA media. The crystallinity of Pt particles prepared in different media increased, following the trend of H2O < H2O/DMF < MEA < DMF. The flower-like Pt structures exhibited a high catalytic performance towards the oxidation of formic acid, as demonstrated by the high electroactive surface area of 0.4058 m2, which was better than Pt black in terms of resistance towards CO poisoning, and showed high stability with current density of 0.41 mA/cm2 for 1000 s. The Pt particles synthesised in MEA exhibited small electroactive area, but more resistance towards CO poisoning as compared to sample prepared in H2O. Therefore, this showed that the catalytic properties of Pt are highly dependent on the faceted structures, whereby large number of edges and corners increased the surface-to-volume ratio, and thus the absorption sites for electrooxidation of formic acid.

Preparation of electrospun polyvinylidene fluoride/amidoximized polyacrylonitrile nanofibers for trace metal ions removal from contaminated water

In this study, a mixture of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and dimethylformamide (DMF) as solvent were reacted with hydroxylamine hydrochloride to produce polyvinylidene fluoride (PVDF)/amidoximized polyacrylonitrile (AOPAN) spinning solution, and then a novel composite PVDF/AOPAN was fabricated by electrospinning technique. Later the electrospun PVDF/AOPAN nanofibers (NFs) were treated with KOH and pitched in (plunged in) mini-column to be used as an adsorbent material under continuous flow. The structural and morphological characterization of nanofibers membrane was determined using scanning electron microscope equipped with an energy dispersive spectrometer(SEM/EDS), Fourier transform infrared spectrometer (FTIR), and goniometer, the inductively coupled plasma optical emission spectrometer (ICP-OES) analysis was used to evaluate the adsorption capability. The effects of pH and metal ions concentration on the transport properties of PVDF/AOPAN nanofibers were also studied. The Langmuir model fits well with isotherm data for lead and copper and the Redlich–Peterson model for nickel, whereas pseudo-second order was the best to clearly delineate the investigated kinetics. The modified PVDF/AOPAN NFs showed excellent adsorption capability with very fast kinetics reaching the equilibrium in 90 min for lead, copper, and 60 min for nickel. EDS analysis of PVDF/AOPAN after metal adsorption confirmed the attachment of the metals. Obtained results illustrate that converting PAN to AOPAN enhanced the hydrophilicity drastically. The removal rate for lead, copper, and nickel reached 99.5% 99.5% 99.6% under 10 mg L−1 respectively, more interestingly for lead, even the concentration was 100 mg L−1, the removal rate still reached 98.1%. Moreover, the adsorbent displayed an excellent regeneration ability by using 0.5 M HCl. This study showed that PVDF/AOPAN is an effective adsorbent for Pb(II), Cu(II), and Ni(II) removal in trace amount.

Effect of solvent on the physicochemical properties of electrospun nanocomposite with gamat oil and cerium oxide for potential medical engineering application

Wound healing is a complex and intricate process that has affected millions of people due to improper management. Scaffolds are capable of exhibiting an environment that is optimum for the regeneration of damaged tissues and hence, enhances the process of wound healing. The current study was done to fabricate nanocomposites composed of polycaprolactone (PCL) as well as gamat oil and cerium (Ce) oxide particles of different ratios through electrospinning that can be used in the healing of wounds. The polymeric solutions were dissolved in two different solvent systems to investigate the influence of solvent parameters on the physical properties of nanofibres. Solvent system A was a mixture of chloroform and dimethylformamide (DMF), while solvent system B was a mixture of acetone and DMF. Morphological analysis of fibre diameter indicated a decrease and the reduction of diameter was more pronounced in solvent system B rather than A. Contact angle measurements revealed that the addition of added constituents to pure PCL have increased its’ hydrophobicity nature for nanocomposites using both solvent systems. Fourier transform infrared spectroscopy (FTIR) results indicated chemical interactions between PCL, gamat oil and cerium oxide as detected through the shift in absorption bands. Lastly, mechanical testing of the nanocomposites indicated that using both solvent systems, there was an increase in the tensile strengths when gamat oil and Ce oxide were added. The newly fabricated nanocomposites using different solvent systems demonstrated physicochemical properties that are well suited for wound healing applications.

Morphology control in PVDF membranes using PEG/PVP additives and mixed solvents

The effects of the mixed two solvents, Dimethylacetamide (DMAc) and Dimethylformamide (DMF), and Polyethylene glycol (PEG) and Polyvinylpyrrolidone (PVP) as additives on performance of Polyvinylidene fluoride (PVDF) membranes were studied. Initially, PEG200 was used as a primary additive at fixed percentage of 5% wt. PVP was then blended with PEG200 in different concentrations. PVDF and DMAc were used as polymer and solvent in the casting solutions, respectively. To control the diffusion rate of PVP in the presence of PEG200 and PVP blend, mixtures of DMAc and DMF were used as the mixed solvent in the casting solutions. Asymmetric PVDF membranes were prepared via phase inversion process in a water bath and the effects of two additives and two solvents on the membrane morphology, pure water flux (PWF), hydrophilicity and rejection (R) were investigated. Attenuated Total Reflection Fourier Transform Infrared Spectra (ATR-FTIR) analysis was used to show the residual PVP on the surface of the membranes. Atomic Force Microscopy (AFM) was utilized to determine roughness of membrane surface. The use of mixed solvents in the casting solution resulted in reduction of PVP diffusion rate and increment of PEG diffusion rate. Eventually, PWF and R values reduced, while porosity and hydrophilicity increased.

Study on hysteresis in perovskite solar cells fabricated using different solvents under ambient conditions

We have investigated the dependency of hysteresis in all-ambient-processed perovskite solar cells on the solvent used for the synthesization of perovskite. Methylammonium lead iodide (MAI) perovskite solar cells have been fabricated using the two-step sequential spin coating method. The influences of PbI2 precursor on the cell performance and its hysteresis are investigated using four different solvents of pure dimethylformamide (DMF), pure dimethyl sulfoxide (DMSO) and mixtures of DMF:DMSO with the ratios of (4:1) and (1:4). The results indicate that a small amount of DMSO in DMF leads to produce large grains of perovskite with proper coverages at the interfaces with hole and electron transport layers. The best conversion efficiency of 10.9% was obtained for the cell prepared by the solvent of (4:1) for DMF:DMSO. The best hysteresis was also obtained from the same cell with the hysteresis index of 0.009.

Low Pressure CO2 Capture with Amide-Based Imprinted Polymers

Bulk polymerization was used to fabricate molecularly imprinted polymer (MIP) adsorbents inherent with amine-functionality for post combustion CO2 capture. Polymerization was performed at 333 K for 24 hours using methacrylamide and ethylene glycol dimethacrylate (EGDMA) as the functional monomer and cross linker respectively, oxalic acid as the template azobisisobutyronitrile (AIBN) as the initiator and 4:1 (v/v) mixture of acetonitrile and dimethylformamide (DMF) as the porogenic solvent. The monolithic polymers were crushed and ground, followed by screening to 75-215 μm and the template was then removed from the polymeric particles by extraction using methanol and hydrochloric acid (90/10 v/v). A fixed bed adsorption column was used to investigate the performance of the dynamic CO2 uptake capacities. The X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared spectroscopy (FT-IR) spectra showed a huge number of -NH2 functionality distributed on the surface of the adsorbents, which thus enhanced the CO2 adsorption uptake. The maximum CO2 capture capacity was found in the MIP with the maximum template concentration (0.40 mmol/g, SBET 258 m2/g at 0.15 bar partial pressure and temperature of 313 K). The MIPs were stable thermally up to 518 K and the isotherms displayed type II revealing a non-uniform distribution of the pore size.

Facile preparation of polybenzoxazine-based carbon microspheres with nitrogen functionalities: Effects of mixed solvents on pore structure and supercapacitive performance

In this study, polybenzoxazine (PBZ)-based carbon microspheres were prepared via a facile method using a mixture of formaldehyde (F) and dimethylformamide (DMF) as the solvent. The PBZ microspheres were successfully obtained at the F/DMF weight ratios of 0.4 and 0.6. These microspheres exhibited high nitrogen contents after carbonization. The microstructures of all the samples showed an amorphous phase and a partial graphitic phase. The porous carbon with the F/DMF ratio of 0.4 showed significantly higher specific capacitance (275.1 F·g−1) than the reference carbon (198.9 F·g−1) at 0.05 A·g−1. This can be attributed to the synergistic electrical double-layer capacitor and pseudo-capacitor behaviors of the porous carbon with the F/DMF ratio of 0.4. The presence of nitrogen/oxygen functionalities induced pseudo-capacitance in the microspheres, and hence increased their total specific capacitance. After activation with CO2, the specific surface area of the carbon microspheres with the F/DMF ratio of 0.4 increased from 349 to 859 m2·g−1 and the specific capacitance increased to 424.7 F·g−1. This value is approximately two times higher than that of the reference carbon. The results indicated that the F/DMF ratio of 0.4 was suitable for preparing carbon microspheres with good supercapacitive performance. The nitrogen/oxygen functionalities and high specific surface area of the microspheres were responsible for their high capacitance.

Electrospinning of polystyrene polybutadiene copolymer for oil spill removal

Cleanup of spilled oil is a difficult process, and it depends on various factors, including the viscosity and the type of the oil spilled, the temperature and the type of water. Oil sorbent nanofibers were prepared from polystyrene polybutadiene copolymer (PSBR) by the electrospinning process using dimethylformamide (DMF), tetrahydrofuran (THF) or mixture of THF and DMF. The fibers surface morphology, crystallinity, hydrophobicity and the sorption capacity, reusability over potable water and seawater were studied. The electrospinning of PSBR in THF produced a structure having a combination of fibers, beads and cup-shaped structures, while the electrospun nanofibers from DMF have more uniform shape and structure. It was found that the average PSBR fibers diameters formed from 10 wt% in THF, DMF and mixture of THF and DMF with the ratio of 50:50 are 80, 1200 and 900 nm, respectively. The results revealed that the contact angle of PSBR fibrous sorbent increased by increasing the concentration of electrospun polymer solution and reached 153 degrees. Moreover, the sorption capacity for crude oil, gas oil and motor oil was 50, 62 and 125 g/g, respectively. The sorption capacity of PSBR nanofibers is higher than regular polystyrene (PS) nanofibers making it a highly promising material for oily water purification.