Standard Organic Solvents Research Articles

Multifaceted insights into pentagonal BeP2 monolayer: From electrochemical to mechanical resilience for alkali-ion batteries using DFT

Herein, we elucidated the properties of a pentagonal BeP2 monolayer, emphasizing its robust dynamic, thermal, and mechanical stabilities, as well as its promising electrochemical characteristics. Combining density functional theory (DFT) with a thermodynamic energy decomposition scheme, we identified BeP2 as a potentially excellent 2D material for energy storage devices. It is characterized by large lattice parameters and semi-metallic behavior, exhibiting a zero density of states (DOS) at the Fermi level. It demonstrates favorable open-circuit voltages, low metal ion migration barriers, and negligible structural modifications for Na and K ions. The specific capacities of Li/Na/K reached remarkable values, surpassing those of most previously reported monolayers. Emerging ion battery technology necessitates solid, directly comparable data to establish an optimized standard organic solvent electrolyte. With this objective in mind, we systematically investigated systems combining two Li/Na/K salts with three different alkyl carbonate solvents. Furthermore, we proposed a defect in BeP2 to explore all possible avenues for sustaining the pentagonal BeP2 monolayer (supplementary Fig. S5 and S6). In summary, our findings strongly indicate that the pentagonal BeP2 monolayer holds considerable promise as an anode material for sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs) owing to its high electrochemical and mechanical sustainability and excellent compatibility with electrolytes.

Addition of allyl Grignard to nitriles in air and at room temperature: experimental and computational mechanistic insights in pH-switchable synthesis.

A straightforward and selective conversion of nitriles into highly substituted tetrahydropyridines, aminoketones or enamines by using allylmagnesium bromide as an addition partner (under neat conditions) and subsequent treatment with different aqueous-based hydrolysis protocols is reported. Refuting the conventional wisdom of the incompatibility of Grignard reagents with air and moisture, we herein report that the presence of water allows us to promote the chemoselective formation of the target tetrahydropyridines over other competing products (even in the case of highly challenging aliphatic nitriles). Moreover, the careful tuning of both the reaction media employed (acid or basic aqueous solutions for the hydrolysis protocol) and the electronic properties of the starting nitriles allowed us to design a multi-task system capable of producing either β-aminoketones or enamines in a totally selective manner. Importantly, and for the first time in the chemistry of main-group polar organometallic reagents in non-conventional protic solvents (e.g., water), both experimental and computational studies showed that the excellent efficiency and selectivity observed in aqueous media cannot be replicated by using standard dry volatile organic solvents (VOCs) under inert atmosphere conditions.

Highly Concentrated Electrolytes for Lithium Sulfur Batteries – the Role of the Anion(s)

Lithium-sulfur batteries (Li-S) have attracted a lot of attention as a alternative/complement to lithium-ion batteries (LIBs) – due to both high energy density, availability, and inexpensive materials used.[1]Yet, dissolution of sulfur from the C/S cathode and subsequent shuttling of lithium polysulfides (LiPS) to the anode as well as the instability of the Li metal anode itself are true scientific and technological challenges. Advancing in the field of electrolytes is one promising way to overcome both issues.Switching from the standard 1 M electrolyte design of LIBs to highly concentrated electrolytes (HCEs) may both prevent the dissolution of LiPSs and hinder dendrite formation at the lithium metal anode.[2]Here we combine experimental methods and computational approaches to investigate several HCEs based on various Li-salts in several standard organic solvents. Experimentally we targeted electrochemical properties, local electrolyte structure, and physico-chemical properties, with focus on the role(s) of the Li-salt anions. Furthermore, to predict the solubility of sulfur the conductor like screening model for real solvents (COSMO-RS), a computational fluid phase thermodynamic approach, was used.[3] Overall, the challenges and opportunities associated with the use of HCEs in Li-S batteries will be addressed, also highlighting potential areas for future research and development.References Peng et al., "Drastic effect of salt concentration in ionic liquid on performance of lithium sulfur battery." Journal of the Electrochemical Society 169.5 (2022): 050515.Suo et al., "A new class of solvent-in-salt electrolyte for high-energy rechargeable metallic lithium batteries." Nature communications 4.1 (2013): 1481.Jeschke and P. Johansson, "Predicting the Solubility of Sulfur: A COSMO‐RS‐Based Approach to Investigate Electrolytes for Li–S Batteries." Chemistry–A European Journal 23.38 (2017): 9130-9136.

Scalable Aqueous Battery Electrode Processing Strategy to Improve High C-Rate Capability of Lithium-Ion Battery Electrodes

N-methyl-2-pyrrolidone (NMP) is a popular solvent in the battery industry, but its environmental impact has caused a shift towards aqueous-based slurry compositions. However, its use is limited in several nations due to its hazardous effects on humans and the environment. Developing environmentally friendly aqueous processing for electrode manufacturing is crucial as a countermeasure. To implement green and sustainable production method, a water-based battery electrode processing is devised to replace NMP, the standard organic solvent. In addition, the manufacturing procedures of lithium-ion battery electrodes must be tuned for the electrodes to provide equivalent performance to those produced by conventional processing. In this study, we developed a simple aqueous battery electrode manufacturing method to form channels to reduce tortuosity and kinetic limitation of thick, high mass loading LIB battery electrodes and, more importantly, to improve rate performance at high C-rate while ensuring scalability and lowering electrode manufacturing cost

Third-order nonlinear optical properties of choline chloride based deep eutectic solvents: Theoretical and experimental studies

In this work, the preparation of three deep eutectic solvents (DES) based on choline chloride as hydrogen bond acceptor and urea, malonic acid, and phenylpropionic acid as hydrogen bond donor is reported. These series of DES were used as models to measure, for the first time, the third-order optical nonlinearities in eutectic solvents. The nonlinear refractive index (n2) originated from the fast electronic response was determined by the close aperture Z-scan technique under excitation of laser ultrafast pulses at 800 nm, resulting in values of the order of ∼3 × 10-16 cm2 W−1, which are similar to those reported recently for ionic liquids. These values are also similar to those exhibited by some traditional polar protic organic solvents such as water and ethanol. At relatively low energy pulses, the DES presented only pure refractive response, but at high energies two of them exhibited nonlinear absorption. On the other hand, ab initio theoretical calculations using density functional theory (DFT) allowed to determine the static and dynamic second hyperpolarizabilities for the DES with M11/6-311G(d,p) level of theory. The tendency of the theoretical results agrees satisfactorily with the values of n2 obtained experimentally. Our results suggest that the presence of aromatic cloud makes that choline chloride:phenylpropionic acid contributes to produce relatively high n2 values. This study provides relevant information to be considered when DES are intended as an alternative to standard organic solvents in the development of photonic materials.

IDF21-0121 NDMA Analytics in Metformin Products: Comparison of Methods and Pitfalls

Background: Since late 2019 concerns regarding trace levels of the N-nitrosamine NDMA in metformin-containing pharmaceuticals have been an issue, as they exceeded the maximum allowable intake of 96 ng/day for a medicine with long-term intake. This has resulted in thorough assessment of the safety of metformin products in this regard by manufactures worldwide. From the early focus on trace NDMA levels in drug substance, the scope of concern quickly expanded to drug products, associated excipients, and the potential for nitrosamine formation in packaging processes. As the scope expanded, the trace analysis challenge has grown. Metformin is made from the starting materials 2-cyanoguanidine and DMA, hence low residual amounts of DMA in the API are unavoidable. Inorganic nitrite is present in trace amounts in many excipients and can react with DMA to form the mutagenic N-nitrosamine NDMA, which needs to be measured in complex drug product formulations. The methods developed in the pharmaceutical industry are validated according to the applicable guidelines. Nevertheless, incorrect measurements can never be fully excluded. In food analysis, environmental analysis and in medical diagnostics, proficiency tests are a common tool to identify and eliminate systematic errors by comparing measurement results from individual laboratories. Aim: Here, we describe the outcome of an across-industry method comparison study for determination of NDMA in metformin-containing drug products between four labs, employing orthogonal mass spectroscopic methods, and discuss how it has helped to identify and mitigate artefactual results due to NDMA in-situ formation in the analytical process. Method: Proficiency testing employing orthogonal mass spectrometric methods was performed between four laboratories in three countries through analysis of different branded metformin-containing products. To exclude bias from sample inhomogeneity, fine powders of test tablets were prepared by one of the participating laboratories. To avoid bias from sample aging, experiments were performed contemporarily. Results: A risk of overestimating NDMA levels has been identified. Notably, special attention must be given to the sample preparation to prevent artefactual formation of NDMA in the extracted sample. Metformin medicines contain DMA in the ppm range, and nitrite in the ppb range, which react in the standard organic solvent DCM to form elevated levels of NDMA. This study has demonstrated that both removal of DMA and nitrite via solvent extraction, and “quenching” the reaction by addition of a nitrosation scavenger are effective remedies. Discussion: Without proper mitigation, NDMA in-situ formation causes overestimation of the NDMA content, which may in turn lead to an overestimation of affected batches and, ultimately, the risk to patients.

Selective chemical degradation of silica sinters of the Taupo Volcanic Zone (New Zealand). Implications for early Earth and Astrobiology.

Most organic matter (OM) on Earth occurs as kerogen-like materials, that is naturally formed macromolecules insoluble with standard organic solvents. The formation of this insoluble organic matter (IOM) is a topic of much interest, especially when it limits the detection of compounds of geomicrobiological interest. For example, studies that search for biomarker evidence of life on early Earth or other planets usually use solvent-based extractions. This leaves behind a pool of OM as unexplored post-extraction residues, potentially containing diagnostic biomarkers. Since the IOM has an enhanced potential for preservation compared to soluble OM, analysing IOM-released biomarkers can also provide even deeper insights into the ecology of ancient settings, with implications for early Earth and Astrobiology investigations. Here, we analyse the prokaryotic lipid biosignature within soluble and IOM of the Taupo Volcanic Zone (TVZ) silica sinters, which are key analogues in the search for life. We apply sequential solvent extractions and a selective chemical degradation upon the post-solvent extraction residue. Moreover, we compare the IOM from TVZ sinters to analogous studies on peat and marine sediments to assess patterns in OM insolubilisation across the geosphere. Consistent with previous work, we find significant but variable proportions-1%-45% of the total prokaryotic lipids recovered-associated with IOM fractions. This occurs even in recently formed silica sinters, likely indicating inherent cell insolubility. Moreover, archaeal lipids seem more prone to insolubilisation as compared to the bacterial analogues, which might enhance their preservation and also bias overall biomarkers interpretation. These observations are similar to those observed in other settings, confirming that even in a setting where the OM derives predominantly from prokaryotic sources, patterns of IOM formation/occurrence are conserved. Differences with other settings, however, such as the occurrence of archaeol in IOM fractions, could be indicative of different mechanisms for IOM formation that merit further exploration.

Effect of benign solvents composition on poly(ε-caprolactone) electrospun fiber properties

Green electrospinning is a flourishing trend in the field of electrospinning (ES) of polymeric/composite materials for biomedical applications. The use of non-toxic solvents instead of the most commonly used solvents in electrospinning is needed to avoid the possible presence toxic solvents traces in the electrospun mats, enhancing their cytocompatibility. It was found that a single solvent or solvent mixtures have a critical role in fiber formation and properties. In this work, fibers in the micro/nanoscale were obtained by electrospinning technique from different poly(ε-caprolactone) (PCL) solutions. Benign solvents (i.e. acetic and formic acids, water and their mixtures) and standard organic solvents for ES (i.e. chloroform) were explored in order to compare the fiber characteristics and properties. Morphology, size, crystallinity, thermal and polymer stability of fibers were analyzed. The obtained results showed the suitability of the use of benign solvents for ES, highlighting that for the use of formic acid the degradation of PCL should be taken into consideration.

Biomass-Derived Poly(ether-amide)s Incorporating Hydroxycinnamates.

Lignin-derived chemicals have great potential as feedstock to produce polymeric materials, due to the low cost and high abundance of lignin biomass. Lignin is one of the few nonpetroleum sources of aromatic carbon, a desirable moiety in high-performance polymers. Herein we describe the synthesis and characterization of a series of 21 poly(ether-amide)s that incorporate hydroxycinnamates derived from lignin. Three different hydroxycinnamates (coumaric acid, ferulic acid, sinapinic acid) were incorporated into dimers, and then copolymerized with a series of seven aliphatic and aromatic diamines via interfacial polymerization. The resultant polymers exhibited poor solubility in standard organic solvents (excluding DMF), but exhibited moderate glass transition temperatures and moderate thermal stabilities. Additionally, the polymers exhibit excellent resistance to hydrolysis. The modularity of this synthetic approach could be used to rapidly generate diverse polymers with a broad range of well-tuned properties.

All Solid State Carbon Based Supercapacitor with Ionogel As Electrolyte

Electrochemical Double Layer Capacitors (EDLCs), so called supercapacitors, represent a growing part of energy storage devices. Their interest lies in their ability to store more energy than conventional capacitors and to deliver more power than secondary batteries. Common supercapacitors involve activated carbon electrodes and organic solvent based electrolytes. These electrolytes have a good ionic conductivity and a broad electrochemical window (2.5 – 2.7 V in symmetric devices) but their liquid state and flammability entail safety issues. Room temperature ionic liquids (RTILs) are under consideration for the replacement of organic electrolytes since they have a fair ionic conductivity (~1-10 mS.cm-1) and a broad temperature operating range, but their main advantage is related to their safety compared to standard organic solvents. Indeed, RTIL show negligible volatility and no flammability when chosen adequately. RTILs are only composed of anions and cations (without any solvent), and are liquid around room temperature. The use of RTIL in different designs can further improve their properties. One of the most interesting examples is their confinement in a host matrix, which prevents from any possible leakage, and in which their liquid state properties are maintained. Such an electrolyte, named ionogel, could permit to increase considerably the safety of energy storage devices such as EDLCs, based on both RTIL properties as well as on their solid-like shaping. Typical activated carbon electrodes (Norit S50 as activated carbon / Super P as conductive carbon / PVDF-HFP as binder with respective proportions 80 / 10 / 10 wt%, overall ~1mg.cm-2) were deposited onto aluminium current collectors for prototyping. The ionogel was synthesized via sol-gel route with alkoxysilane as silica precursor, RTIL as solvent and formic acid as sol-gel catalyst: the resulting monolithic mesoporous silica hosts the RTIL. The reactants were mixed and casted onto carbon electrodes during a single step process. At the same time, a thick, self-standing, ionogel was made for ionic conductivity measurements. After 5 days of aging, the ionogel was dried in a Buchi (60°C, 0.5 mbar) overnight to remove the residual water. The ionic conductivity of the ionogel, measured in a Swagelok cell under argon, was 1.5 mS.cm-1 at 20 °C. A symmetric all solid state EDLC was assembled using two carbon electrodes with ionogel deposit. After drying following previous process, the device was compared with an EDLC using glass microfiber separator impregnated with the same pristine RTIL. All electrochemical measurements were performed under argon. Cyclic voltammetry experiments demonstrated no capacitance loss when the ionogel was used instead of the pristine RTIL, and the electrochemical stability was maintained up to 2.5 V. An acceptable value at 80 F.g-1 for the gravimetric capacitance was reached ();this showed a good impregnation of the activated carbon by either the pristine RTIL or by the ionogel’ sol precursors. Galvanostatic cycling were performed between 0 V and 2.5 V at 1 mA.g-1 for 10,000 cycles with efficiency above 98 % and no significant capacitance loss.

Structure of Spontaneously Formed Solid-Electrolyte Interphase on Lithiated Graphite Determined Using Small-Angle Neutron Scattering

We address the reactivity of lithiated graphite–anode material for Li-ion batteries with standard organic solvents used in batteries (ethylene carbonate and dimethyl carbonate) by following changes in neutron scattering signals. The reaction produces a nanosized layer, the solid-electrolyte interphase (SEI), on the graphite particles. We probe the structure and chemistry of the SEI using small-angle neutron scattering (SANS) and inelastic neutron scattering. The SANS results show that the SEI fills 20–30 nm sized pores, and inelastic scattering experiments with H/D substitution show that this “chemical” SEI is primarily organic in nature; that is, it contains a large amount of hydrogen. The graphite–SEI particles show surface fractal scattering characteristic of a rough particle–void interface and are interconnected. The observed changes in the SEI structure and composition provide new insight into SEI formation. The chemically formed SEI is complementary and simpler in composition to the electrochemicall...

New Trends in the Separation of Significant Greenhouse Gases from Flue Gas Streams

The paper is closely related to the challenge of the most important greenhouse gas - carbon dioxide. Both, the effective capture and secure storage of CO2, is an urgent environmental problem. Approximately ¾ of all anthropogenic emissions of CO2are related to the use of fossil fuels. Great attention is given to the absorption processes for the capture of the gas. Carbon Capture and Storage (CCS) is a promising solution for achieving a significant reduction in CO2- emissions. Capture of combustion gases using standard volatile organic solvents are the source of numerous problems like environmental pollution, instability and corrosivity of such solvents. An effective solution seems to be the use of ionic liquids. Ionic liquids are a relatively new class of compounds, which are chemically and thermally stable and are able to dissolve a wide range of substances. The negligible volatility of ionic liquids is their most important property. Research and development of the CO2- capture technology has not yet reached the stage of commercial exploitation under economically acceptable conditions. The aim of this article is to show the possibilities of use of ionic liquids in the absorption separation processes for CO2-capture.

All Solid State Activated Carbon Supercapacitor with Silica Ionogel As Electrolyte

Electrochemical Double Layer Capacitors (EDLCs), so called supercapacitors, represent a growing part of energy storage devices. Their interest lies in their ability to store more energy than conventional capacitors and to deliver more power than secondary batteries. Common supercapacitors involve activated carbon electrodes and organic solvent based electrolytes. These electrolytes have a good ionic conductivity and a broad electrochemical window (2.5 – 2.7 V in symmetric devices) but their liquid state and flammability entail safety issues.Room temperature ionic liquids (RTILs) are under consideration for the replacement of organic electrolytes since they have a fair ionic conductivity (~1-10 mS.cm-1) and a broad temperature operating range, but their main advantage is related to their safety compared to standard organic solvents. Indeed, RTIL show negligible volatility and no flammability when chosen adequately. RTILs are only composed of anions and cations (without any solvent) and are liquid around room temperature. The use of RTIL in different designs can further improve their properties. One of the most interesting examples is their confinement in a host matrix, which prevents from any possible leakage, and in which their liquid state properties are maintained. Such an electrolyte, named ionogel, could permit to increase considerably the safety of energy storage devices such as EDLCs, based on both RTIL properties as well as on their solid-like shaping.Typical activated carbon electrodes (Norit S50 as activated carbon / Super P as conductive carbon / PVDF-HFP as binder with respective proportions 80 / 10 / 10 wt%, overall ~1mg.cm-2) were deposited onto aluminium current collectors for prototyping. The ionogel was synthesized via sol-gel route with alkoxysilane as silica precursor, RTIL as solvent and formic acid as sol-gel catalyst: the resulting monolithic mesoporous silica hosts the RTIL. The reactants were mixed and casted onto carbon electrodes during a single step process. At the same time, a thick, self-standing, ionogel (Fig. C) was made for ionic conductivity measurements. After 5 days of aging, the ionogel was dried in a Buchi (60°C, 0.5 mbar) overnight to remove the residual water. The ionic conductivity of the ionogel, measured in a Swagelok cell under argon, was 1.5 mS.cm-1at 20 °C.A symmetric all solid state EDLC was assembled using two carbon electrodes with ionogel deposit. After drying following previous process, the device was compared with an EDLC using glass microfiber separator impregnated with the same pristine RTIL. All electrochemical measurements were performed under argon. Cyclic voltammetry experiments (Fig. A) demonstrated no capacitance loss when the ionogel was used instead of the pristine RTIL, and the electrochemical stability was maintained up to 2.5 V. An acceptable value at 80 F.g-1 for the gravimetric capacitance was reached; this showed a good impregnation of the activated carbon by either the pristine RTIL or by the ionogel sol precursors. Galvanostatic cycling was performed between 0 V and 2.5 V at 1 mA.g-1 for 10,000 cycles (Fig. B) with efficiency above 98 % and no significant capacitance loss.Figure : (A) Cyclic voltammetry (0 to 3V) at different scan rates (2, 5 and 10 mV.s-1) with ionogel (▬) and RTIL (―) electrolytes.(B) Long term cycling behaviour of EDLC with ionogel electrolyte : charge(▬) and discharge (―) capacitances obtained with galvanostatic cycling I=1mA.cm-2(~1A.g-1).(C) 1 cm diameter transparent solid ionogel.Reference: All solid state symmetrical activated carbon Electrochemical Double Layer Capacitor using ionogel made of mesoporous silica confined ionic liquid as electrolyte,M. Brachet, T. Brousse, J. Le Bideau, submitted to Electrochemistry Communications.

Isolation of Alpaca Anti-Idiotypic Heavy-Chain Single-Domain Antibody for the Aflatoxin Immunoassay

Anti-idiotypic antibodies recognize the antigenic determinants of an antibody, thus they can be used as surrogate antigens. Single-domain antibodies from camlid heavy-chain antibodies with the benefit features of small size, thermostability, and ease in expression, are leading candidates to produce anti-idiotypic antibodies. In this work, we constructed an antibody phage library from the mRNA of an alpaca immunized with an antiaflatoxin monoclonal antibody (mAb) 1C11. Three anti-idiotypic VHH antibodies were isolated and applied to immunoassay toward aflatoxin as a coating antigen. The best immunoassay developed with one of these VHH antibodies shows an IC50 of 0.16 ng/mL toward aflatoxin B1 and cross-reactivity toward aflatoxin B2, G1, and G2 of 90.4%, 54.4%, and 37.7%, respectively. The VHH-based immunoassay was successfully applied to the analysis of peanuts, corn, and rice, which are the predominant commodities regularly contaminated by aflatoxins. A good correlation (r(2) = 0.89) was found between the data obtained from the conventional ELISA and the ELISA based on a VHH coating antigen for the analysis of aflatoxins in peanuts and feedstuff. The use of biotechnology in developing the surrogate, the absence of standard aflatoxin and organic solvents in the synthesis procedures, and the reproducibility of the VHH antibody makes it an ideal strategy for replacing conventional synthesized antigens.

Stability of the surface termination of differently modified ultrananocrystalline diamond/amorphous carbon composite films

We have investigated the stability of the surface termination of ultrananocrystalline diamond/amorphous carbon (UNCD/a-C) composite films after their modification with UV/O3 treatments or NH3-containing plasmas. The films were prepared by microwave plasma chemical vapor deposition from CH4/N2 mixtures and possess the H-termination typical for all CVD grown diamond films. The treatment with UV/O3 or NH3/N2 plasma resulted in a change of the surface termination as revealed by contact angle measurements and X-ray photoelectron spectroscopy (XPS). Both processes rendered the as-grown hydrophobic UNCD surface hydrophilic; the influence of the treatment time as well as that of the carrier gas (N2 or Ar) for the plasma process were investigated. The main task of this investigation was to determine the stability of the surface termination with storage time and storage conditions and upon exposure to standard organic solvents, like acetone, ethanol and i-propanol. It was found that for the UV/O3 treated UNCD surfaces the storage in air, and after NH3/N2 plasma modification package under reduced pressure preserved to a great extent the achieved hydrophilic properties in a period up to three months. The changes that occur predominantly during the first days after the modification step were due mostly to interchange of surface groups with the ambient. Similar processes were observed after exposure of the UNCD surfaces to standard organic solvents.

Synthesis, structural investigations, and DFT calculations on novel 3-(1,3-dioxan-2-yl)-10-methyl-10H-phenothiazine derivatives with fluorescence properties

Comparison studies on the acetalization of 10-methyl-10H-phenothiazine-carbaldehyde with 1,3-propanediol, or 2-substituted-1,3-propanediols, under conventional versus microwave assisted conditions and standard organic solvents versus water, were performed as an attempt toward more environmentally benign synthetic methods. New 3-(1,3-dioxan-2-yl)-10-methyl-10H-phenothiazine derivatives were obtained in high yields by azeotropic distillation of water and in moderate yields by microwave assisted synthesis in different solvents, including water under superheated conditions. The solvent influence upon stabilizing the key intermediates involved in the acetalization mechanism was assumed based on DFT calculations, which indicated a favorable enthalpy profile in water solvent. Structural investigations of the new compounds based on spectroscopic methods (NMR, FT-IR, UV–vis, and MS), were completed with molecular mechanics and semi-empirical DFT calculations, which supported an anancomeric chair conformation of the 1,3-dioxane ring with the phenothiazine substituent in the equatorial position and possible free rotation about the single bond linking the two heterocyclic units. The new compounds display daylight fluorescence characterized by remarkably large Stokes shifts determined by LE spectroscopy.

Preparation and characterization of chitosan-hydroxybenzotriazole/polyvinyl alcohol blend nanofibers by the electrospinning technique

Abstract Nanofibers of a chitosan-hydroxybenzotriazole (CS-HOBt)/polyvinyl alcohol (PVA) blend were successfully prepared using electrospinning techniques. In this study, nanofibers were fabricated without the use of standard organic solvents or organic acids. CS was dissolved with HOBt in distilled water, and this solution of CS-HOBt (2 wt%) with PVA (10 wt%), blended in different weight ratios, was electrospun to obtain nanofibers. The morphology, diameter, and structure of the electrospun nanofibers were investigated. SEM images showed that the morphology and diameter of the nanofibers were mainly affected by the weight ratio of the blend. Nanofibers were observed when the CS content was less than 50 wt%. The average diameter of the nanofibers was 190–282 nm, and this average diameter gradually decreased with increasing CS content. Cytotoxicity tests of the nanofiber mats showed that the fibers were non-toxic to human fibroblast cells. Hence, these biodegradable nanofibers may be suitable for drug delivery or tissue engineering applications.

Perfluorocarbon Soluble Crown Ethers as Phase Transfer Catalysts

AbstractFluorous derivatives of dibenzo‐18‐crown‐6 ether were readily prepared by means of metal‐catalyzed cross‐coupling reactions, and then successfully applied as catalysts in representative solid‐liquid phase transfer catalysis (PTC) reactions, which were performed in standard organic solvents, such as chlorobenzene and toluene, and also in fluorous solvents, such as perfluoro‐1,3‐dimethylcyclohexane (PFDMC). It was clearly shown that properly designed fluoroponytailed crown ethers can promote the disintegration of the crystal lattice of alkali salts and transfer anions from the solid surface into an apolar, non‐coordinating perfluorocarbon phase. Far from being a simple chemical curiosity, this unprecedented observation has relevant implications in the design of PTC scenarios of wide applicability. This new paradigm represents an advance in crown ether chemistry, and their use as recyclable phase transfer catalysts.

Tetrafluoro‐IBA and‐IBX: Hypervalent Iodine Reagents

Fluorine makes the difference: FIBX (see structure), the tetrafluoro derivative of the hypervalent iodine reagent, is more soluble and has higher reactivity than its nonfluorinated counterpart. An efficient synthesis of FIBX and initial reactions are presented. Some of these reactions can be conducted in standard organic solvents. Owing to the increased reactivity, new transformations and catalytic reactions may be possible.

New Amorphous Fluoropolymers of Tetrafluoroethylene with Fluorinated and Non-Fluorinated Tricyclononenes. Semiconductor Photoresists for Imaging at 157 and 193 nm

Twenty-two tricyclo[4.2.1.02,5]non-7-ene (TCN) or 3-oxatricyclononene monomers, having fluorinated or nonfluorinated substituents on the four-membered rings, were prepared by cycloaddition reactions of functionalized olefins with norbornadiene or quadricyclane. Radical polymerizations with tetrafluoroethylene (TFE) and/or TFE and acrylates provided amorphous polymers with high solubility in standard organic solvents. The TFE/TCN dipolymers typically have glass transition temperatures of over 200 °C, substantially higher than TFE copolymers with norbornene. Perfluoroalkyl sulfonyl fluoride groups can be incorporated in the side chains of the TCN monomers giving soluble copolymers. Polymers which also incorporated acrylate monomers were prepared using a semibatch process to control composition. Selected polymers incorporating tertiary alkyl ester groups from the TCN monomer or acrylates have shown good image formation when compounded with a photoacid generator, imaged with 157 or 193 nm light, and developed using aqueous base.