Solutions In Organic Solvents Research Articles

Optimization of ethyl lactate‐based organosolv process for lignin recovery from the solid waste of a wheat straw biorefinery

AbstractBACKGROUNDThe organosolv process promotes biomass delignification at relatively high temperatures using a wide variety of organic solvent solutions. Nevertheless, previous studies on organosolv processes have not dealt with the use of ethyl lactate as organic solvent. Thus the aim of the present contribution was to determine and to validate if the use of ethyl lactate has a positive influence on lignin recovery for organosolv processes whose feedstock is the solid waste from a wheat straw‐based biorefinery. The effect of operating conditions (temperature and time) on lignin recovery was also studied.RESULTSA mixed design of experiments was proposed as the strategy to maximize lignin recovery. The mathematical model derived from a multiple linear regression applied to the mixed design results indicates that 190 °C and a non‐aqueous solution containing ethyl lactate and ethanol (81.2% w/w ethyl lactate) could provide a maximum lignin recovery of 75.9% w/w. This theoretical maximum was validated. Thus the proposed model adequately describes the behavior of lignin recovery. Moreover, Fourier transform infrared (FTIR) characterization of the resultant lignin suggested that its structure is a function of the organic solvent solution used during the organosolv process.CONCLUSIONThe evidence from this study indicates that lignin recovery from the solid waste of a wheat straw‐based biorefinery in an organosolv process depends on temperature and ethyl lactate presence in the reaction medium. These findings enhance the understanding of organosolv processes and could be applied if eventual lignin valorization is desired. © 2019 Society of Chemical Industry

ПОЛИЭФИРИМИДЫ ДЛЯ СОЗДАНИЯ ТЕПЛОСТОЙКИХ ПОЛИМЕРНЫХ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ С ВЫСОКИМИ ФИЗИКО-МЕХАНИЧЕСКИМИ СВОЙСТВАМИ

Thermoplastic and soluble in organic solvents polyetherimide is of great interest for the creation of heat-resistant composite materials with high physical and mechanical properties. In recent decades, the main scientific approaches to the synthesis of polyimides with the ability to process from melt and solutions in organic solvents have been developed. According to this methodology, the glass transition temperature of rigid-chain polyimides is reduced by increasing the flexibility of the main polymer chain and/or by reducing the intermolecular interaction. 
 Evolution of fine organic synthesis is one of the priority directions of development of chemical technology. Chemistry of high-molecular compounds is the subject of research by various domestic and foreign scientists. This interest is due to the prospects for the use of materials for industrial purposes. The polyetherimide contains various aromatic, heterocyclic and cycloaliphatic groups and systems in its chain. This article describes the main approaches to the creation of polymers with improved, compared with polyimides, technological properties and prospects for their application in the production of filled composite materials based on them. The paper presents the properties of the materials under consideration as a justification for the creation of heat-resistant composite materials.

Structure Water-Solubility Relationship in α-Helix-Rich Films Cast from Aqueous and 1,1,1,3,3,3-Hexafluoro-2-Propanol Solutions of S. c. ricini Silk Fibroin.

Silk fibroin (SF) produced by the domesticated wild silkworm, Samia cynthia ricini (S. c. ricini) is attracting increasing interest owing to its unique mechanical properties, biocompatibility, and abundance in nature. However, its utilization is limited, largely due to lack of appropriate processing strategies. Various strategies have been assessed to regenerate cocoon SF, as well as the use of aqueous liquid fibroin (LFaq) prepared by dissolution of silk dope obtained from the silk glands of mature silkworm larvae in water. However, films cast from these fibroin solutions in water or organic solvents are often water-soluble and require post-treatment to render them water-stable. Here, we present a strategy for fabrication of water-stable films from S. c. ricini silk gland fibroin (SGF) without post-treatment. Aqueous ethanol induced gelation of fibroin in the posterior silk glands (PSG), enabling its separation from the rest of the silk gland. When dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), the SGF-gel gave a solution from which a transparent, flexible, and water-insoluble film (SGFHFIP) was cast. Detailed structural characterization of the SGFHFIP as-cast film was carried out and compared to a conventional, water-soluble film cast from LFaq. FTIR and 13C solid-state NMR analyses revealed both cast films to be α-helix-rich. However, gelation of SGF induced by the 40%-EtOH-treatment resulted in an imperfect β-sheet structure. As a result, the SGF-gel was soluble in HFIP, but some β-sheet structural memory remains, and the SGFHFIP as-cast film obtained has some β-sheet content which renders it water-resistant. These results reveal a structure water-solubility relationship in S. c. ricini SF films that may offer useful insights towards tunable fabrication of novel biomaterials. A plausible model of the mechanism that leads to the difference in water resistance of the two kinds of α-helix-rich films is proposed.

Structure solution and analyses of the first true lipase obtained from metagenomics indicate potential for increased thermostability

Metagenomics is a modern approach to discovery of new enzymes with novel properties. This article reports the structure of a new lipase, belonging to family I.1, obtained by means of metagenomics. Its structure presents a fold typical of α/β hydrolases, with the lid in closed conformation. The protein was previously shown to present high thermostability and to be stable in aqueous solutions of polar organic solvents at high concentrations [30% (V/V)]. Molecular dynamics studies showed that the protein maintains its structure well in organic solvents. They also suggested that its thermostability might be enhanced if it were mutated to present a disulfide bond similar to that typically found in lipase family I.2. These findings identify this lipase as a good candidate for further improvement through protein engineering.

Stimuli‐Responsive Copolymer and Uniform Polymeric Nanoparticles with Photochromism and Switchable Emission

AbstractAn efficient approach to make a fluorescent polymer both photoswitchable and stimuli‐responsive was successfully developed by rationally introducing a photochromic bisthienylethene derivative (BTE) and fluorescent 4‐dicyanomethylene‐2,6‐distyryl‐4H‐pyran derivative (DPC) units in the side chains via copolymerization. Benefiting from the reversible photocyclization of BTE and the intermolecular Förster Resonance Energy Transfer (FRET) effect from DPC to the closed form of BTE, the emission signatures of the polymer both in solution in organic solvents and in thin films could be tuned by the alternating irradiation of ultraviolet and visible light. Moreover, uniform polymeric nanoparticles (NPs) with reversibly photoswitchable fluorescence properties were synthesized using a facile one‐step mini‐emulsion polymerization. This polymer could act as a smart material for photoresponsive polymer illuminants and offers new platform for multifunctional molecular switching and multi‐responsive materials.

Microheterogeneity and CO2 Switchability of N, N-Dimethylcyclohexylamine-Water Binary Mixtures.

Binary mixtures of water and organic solvents are described as the aqueous solutions of organic solvents, which are usually spatially heterogeneous on the scale of a few molecular sizes but homogeneous on longer length scales, that is, microheterogeneity. For the water-organic solvent binary mixtures with microheterogeneity, most organic solvents are miscible with water at any ratio. Interestingly, some slightly water-miscible organic solvents can also be used to prepare binary mixtures with microheterogeneity. In this study, N, N-dimethylcyclohexylamine (DMCHA) was used to prepare binary mixtures with microheterogeneity and CO2 switchability. With the help of conductivity, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and dynamic light scattering measurements, we found that water molecules are hydrogen-bonded together to form clusters over the water content range of 9 to 27 wt %, exhibiting microheterogeneity in the binary mixture. The size of the water clusters increases slightly with increasing water content. What is more, the DMCHA-water mixtures can be reversibly split into two phases by alternate bubbling of CO2 and N2, exhibiting excellent CO2 switchability. The binary mixtures can be used as reaction media for the synthesis of CaCO3 nanoparticles. Binary mixtures with microheterogeneity can also be formed under high salinity or high temperature conditions or be prepared using other slightly water-miscible organic solvents, opening up more interesting possibilities for binary mixtures with microheterogeneity.

Solubility Determination and Modeling for Artesunate in Binary Solvent Mixtures of Methanol, Ethanol, Isopropanol, and Propylene Glycol + Water

Artesunate is dissolved in an aqueous solution of several organic solvents (methanol, ethanol, isopropanol, and PG), and the mole fraction of artesunate is determined by the static method. When the system reaches equilibrium, the range of system temperature is 278.15–318.15 K and the pressure environment is 101.1 kPa. When the temperature is constant, the equilibrium mole fraction of artesunate is proportional to the mass percentage of organic solvents, and the relationship between artesunate solubility and temperature is the same as before under certain conditions of the organic solvent component. When the external conditions are the same, artesunate is more likely to dissolve in the ethanol + water mixture than in several other systems. Besides, three classical mixed solvent thermodynamic equations—Jouyban–Acree model, van’t Hoff–Jouyban–Acree model, and Apelblat–Jouyban–Acree model—are applied to calculate the equilibrium mole fraction of artesunate. The maximum value of average relative deviations (AR...

Saponin-Based Near-Infrared Nanoparticles with Aggregation-Induced Emission Behavior: Enhancing Cell Compatibility and Permeability

Fluorescence imaging is critical for physiological activities and cell biology but limited by the poor solubility, cell compatibility, and permeability. Herein, we develop a novel engineering methodology to prepare biocompatible and penetrable aggregation-induced emission (AIE) nanoparticles with the assistance of flash nanoprecipitation (FNP) technology. On the basis of the donor-π-acceptor (D-π-A) system, the AIE building block of tricyano-methylene-pyridine (TCM) is fine-tuned to long emission wavelength by modulating the π-conjugation bridge and electron-donating group, thereby achieving high solid fluorescent quantum yield, near-infrared (NIR) characteristic, large Stokes shift, and excellent photostability. On the basis of the FNP technology, the amphiphilic saponin solution and TCMN-5 in organic solvent are quickly mixed in the multi-inlet vortex mixer (MIVM), followed by saponin-encapsulation of the hydrophobic AIE nucleation with inhibiting further growth of nanoparticles. The biocompatible amphiphilic saponin such as α-hederin can encapsulate and micellize the AIE TCM fluorophore for efficient cell imaging. The kinetic FNP technology can not only modulate the uniform diameter size, but also distinctly increase the micelle stability when compared to the conventional thermodynamic self-aggregation method, which provides an alternative opportunity for scale-up preparation of drugs and probes in delivery vehicles.

Bulk Nanobubbles from Acoustically Cavitated Aqueous Organic Solvent Mixtures

We investigate the existence and stability of bulk nanobubbles in various aqueous organic solvent mixtures. Bulk nanobubble suspensions generated via acoustic cavitation are characterized in terms of their bubble size distribution, bubble number density, and zeta potential. We show that bulk nanobubbles exist in pure water but do not exist in pure organic solvents, and they disappear at some organic solvent-water ratio. We monitor the nanobubble suspensions over a period of a few months and propose interpretations for the differences behind their long-term stability in pure water versus their long-term stability in aqueous organic solvent solutions. Bulk nanobubbles in pure water are stabilized by their substantial surface charge arising from the adsorption of hydroxyl ions produced by self-ionization of water. Pure organic solvents do not autoionize, and therefore, nanobubbles cannot exist in concentrated aqueous organic solvent solutions. Because of preferential adsorption of organic solvent molecules at the nanobubble interfaces, the surface charge of the nanobubbles decreases with the solvent content, but the strong hydrogen bonding near their interfaces ensures their stability. The mean bubble size increases monotonically with the solvent content, whereas the surface tension of the mixture is sharply reduced. This is in agreement with literature results on macro- and microbubbles in aqueous organic solutions, but it stands in stark contrast to the behavior of macro- and microbubbles in aqueous surfactant solutions.

Synthesis of functionalized magnetite nanoparticles using only oleic acid and iron (III) acetylacetonate

The solvothermal method is a way to obtain magnetite nanoparticles with uniformity in shape and size, good dispersibility and functionalized surface. These properties are desirable in many applications in materials science and medical area. Although methods for obtaining nanoparticles with these properties are reported, the most their use several reagents to act as solvent, surfactant and reducing agent, which makes the synthesis process more difficult and expensive. In this paper, we introduced a simple method for the preparation of magnetite nanoparticles using only iron (III) acetylacetonate as metal precursor and oleic acid for all the other functions. This is possible due the constant liberation of the acetylacetone formed in the reaction, which favors the formation of the oleate, the responsible for the conditions required to obtain magnetite nanoparticles smaller than 20 nm. By this method, nanoparticles were obtained with an average size of 17 nm in a narrow size distribution, uniformity of morphology, high crystallinity and functionalized surface. The organic capping layer allows the preparation of stable colloidal solutions in organic solvents and facilitates the posterior use of nanoparticles in films, ferrofluids and nanocomposite preparation.

A Simple Theoretical Approach of Aqueous Solutions of Salts and Organic Solvents in Paper Chromatography

The purpose of this study is to determine the properties of the solvents responsible of the chromatographic phenomenon. A simple and homogeneous system of ascending chromatography on paper is described, allowing varying only one of the factors constituting it. This method made it possible to determine constants by means of a simple equation. The validity of the method is deduced from the good agreement between its mathematical expression and the experimental values obtained.

Poly(2-oxazoline)s terminated with 2,2'-imino diacetic acid form noncovalent polymer-enzyme conjugates that are highly active in organic solvents.

A great limitation for the usability of free enzymes in organic solvents is their insolubility in these media. Some surfactants are capable of solubilizing enzymes in such media, but they are hard to remove. Covalent modification of enzymes with polymers has led to polymer-enzyme conjugates (PECs) that are soluble in organic solvents, but the process is quite elaborate. Poly(2-oxazoline)s (POx) with the end group 2,2'-imino diacetic acid were shown to form reversible, nano-sized noncovalent aggregates with enzymes. These PECs give clear solutions in organic solvents. The enzymes lysozyme, horseradish peroxidase (HRP), laccase, α-chymotrypsin (CT), catalase, and alcohol dehydrogenase could be solubilized in chloroform and toluene at concentrations of up to 2 mg protein/ml. Laccase, HRP, and CT were shown to survive the transfer into the organic medium and back to water in their active form. The distribution coefficient of the proteins between water and the organic solvent was shown to be dependent on the nature of the POx backbone. All three biocatalysts exhibit greatly enhanced activity in the respective organic solvent.

Understanding the effect of molecular solvents on the microscopic network of DBU imidazole ionic liquid

In order to uncover the microscopic structure of ionic liquids (ILs) in solutions of organic solvents, a protic ionic liquid, prepared from superbase 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with imidazole, which is so-called [HDBU]IM, has been synthesized. And the 1H NMR chemical shifts of binary mixtures, namely [HDBU]IM/ dimethyl sulfoxide (DMSO), [HDBU]IM/dimethylformamide (DMF) and [HDBU]IM/ethanol were measured at 298.15 K within whole concentrations range, which were correlated using the local composition (LC) model to obtain the local mole fractions. In addition the excess molar volumes VE and excess Gibbs energy of activation for viscous flow ΔG⁎E were calculated from experimental data of densities ρ and viscosities η of mixtures. Moreover electrical conductivities κ of all solutions were measured and correlated using empirical Casteel-Amis equation. LC analysis deduced from 1H NMR chemical shifts shows that the ability of organic solvents to destroy the network of [HDBU] IM could follow this order: ethanol>DMF > DMSO, which is consistent with the variation of VE, κ and ΔG⁎E values.

Synthesis and characterization of bacteriochlorin loaded magnetic nanoparticles (MNP) for personalized MRI guided photosensitizers delivery to tumor

HypothesisHydrophobic bacteriochlorin based photosensitizer (PS) can be effectively immobilized on MNP covered by human serum albumin (HSA). PS loading into MNP protein shell allows solubilizing PS in water solution without altering its photodynamic activity. MNP@PS can serve as diagnostic tool for tracking PS delivery to tumor tissues by MRI. ExperimentsImmobilization on MNP-HSA-PEG was performed by adding PS solution in organic solvents with further purification. MNP@PS were characterized by DLS, HAADF STEM and AFM. Absorbance and fluorescence measurements were used to assess PS photophysical properties before and after immobilization. MNP@PS internalization into CT26 cells was investigated by confocal microscopy in vitro and MRI/IVIS were used for tracking MNP@PS delivery to tumors in vivo. FindingsMNP@PS complexes were stable in water solution and retained PS photophysical activity. The length of side chain affected MNP@PS size, loading capacity and cell internalization. In vitro testing demonstrated MNP@PS delivery to cancer cells followed by photoinduced toxicity. In vivo studies confirmed that as-synthetized complexes can be used for MRI tracking over drug accumulation in tumors.

Microfluidic Inverted Flow of Ternary Water/Hydrophilic/Hydrophobic Organic Solvent Solution in a Y-Type Microchannel and a Proposal of the Response Microfluidic Analysis through the Experiment.

Two solutions that are individually fed at the same flow rate into two separate microchannels of a microchip, combine to form a single channel (a Y-type microchannel). This flow is either parallel for immiscible solutions or initially parallel, but then becomes homogeneous through diffusion, for miscible solutions. However, a new type of microfluidic behavior in a Y-type microchannel that was neither parallel nor homogeneous flow has been observed using, for example, water/acetonitrile (3:4.5, v/v) and acetonitrile/ethyl acetate (3.5:4, v/v) mixed solutions. Each mixed solution was marked with distinctive dyes and delivered at the same flow rate into a Y-type microchannel under laminar flow conditions. In the single channel, the two phases were initially observed to flow in parallel, but then apparently swapped to flow on the opposite wall while retaining parallel flow with a slight change in the components of the two phases. We have named this type of laminar flow "microfluidic inverted flow" for ternary water/hydrophilic/hydrophobic organic solvent mixed solutions. The inverted flow of a ternary water/acetonitrile/ethyl acetate system was examined in detail under various flow conditions. We also proposed a concept of response microfluidic analysis based on such microfluidic inverted flow.

Solvent-Tuned Supramolecular Assembly of Fluorescent Catechol/Pyrene Amphiphilic Molecules.

The synthesis and structuration of a novel low-molecular-weight amphiphilic catechol compound is reported. The combination of a hydrophilic tail containing a catechol unit and a pyrene-based hydrophobic head favors solvent-tuned supramolecular assembly. Formation of hollow nanocapsules/vesicles occurs in concentrated solutions of polar protic and nonprotic organic solvents, whereas a fibril-like aggregation process is favored in water, even at low concentrations. The emission properties of the pyrene moiety allow monitoring of the self-assembly process, which could be confirmed by optical and electronic microscopy. In organic solvents and at low concentrations, this compound remains in its nonassembled monomeric form. As the concentration increases, the aggregation containing preassociated pyrene moieties becomes more evident up to a critical micellar concentration, at which vesicle-like structures are formed. In contrast, nanosized twist beltlike fibers are observed in water, even at low concentrations, whereas microplate structures appear at high concentrations. The interactions between molecules in different solvents were studied by using molecular dynamics simulations, which have confirmed different solvent-driven supramolecular interactions.

An Alternative Method for Correlation and Evaluation of Mutual Diffusion Coefficients of Solutes in Organic Solvents at Infinite Dilution

Based on the linear free energy relationships theory and empirical equations, correlations of mutual diffusion coefficients of solutes in organic solvents at infinite dilution at various temperatures are proposed. Four homologues in 743 binary systems have been regressed and correlation equations for the diffusion coefficients are obtained. The mean relative deviations of the four equations are 8.63%, 8.57%, 2.96%, and 4.85%, and all of the squared correlation coefficients (R2) are larger than 0.96, indicating that the fittings are good. The results reveal that a simple form of the equation exhibits high estimation accuracy, definite theory meaning, wide applicability and wide temperature range. This study successfully combines macroscopic physical properties of substances with their molecular microstructure, providing an alternative approach for calculating of mutual diffusion coefficient.

Polycaprolactone foams prepared by supercritical CO2 batch foaming of polymer/organic solvent solutions

In this work, the batch foaming of polymeric solutions by means of supercritical CO2 (scCO2) is described. The developed process combines the advantages of processing materials from solution in organic solvents and scCO2 batch foaming to prepare foams with uniform and controllable porosity. Polycaprolactone (PCL) was selected as semi-crystalline polymer as a case study and foams from solutions in different scCO2-miscible organic solvents, namely ethyl acetate, chloroform, dioxane and dimethyl sulfoxide, were prepared.Obtained results demonstrate that processing PCL solutions by means of scCO2 batch foaming enables preparing solid polymeric foams with solvent residue close to 1 wt. %, density values in the 0.2–0.5 g/cm3 range, hundreds of microns pore size and pore walls with spherulitic morphology. The advantage of this process is herein demonstrated by the fabrication of composite PCL foams containing 30 w% of either inorganic TiO2 nanoparticles and 5-fluorouracil chemotherapeutic by processing polymeric solutions in a single step.

Structure-fluorescence relationships in 2-aryl-5-(2′-aminophenyl)-4-hydroxy-1,3-thiazoles

Five substituted 2-aryl-4-hydroxy-5-(2′-aminophenyl)-1,3-thiazoles have been studied for their fluorescence properties under neutral and alkaline conditions in solutions of various organic solvents. From comparison with the analogous 2-aryl-4-hydroxy-5-(2′-hydroxyphenyl)-1,3-thiazoles it is clear that both in neutral as well as in the deprotonated state the presence of the 2′-amino group lowers the fluorescence quantum yields (Φ). Introduction of an electron withdrawing groups into the 2-aryl group further decreases Φ. Upon deprotonation of the 4-hydroxy group a large bathochromic shift of the absorption (ΔλA = 100–125 nm) as well as emission (ΔλF = 100–120 nm) bands occurs. An intramolecular hydrogen bond between the amino and hydroxyl groups is obvious. The first absorption band of all studied compounds corresponds to a π-π* HOMO-LUMO transition with a CT character. Thiazoles 3b-f and their deprotonated forms 3b–-f– display fluorescence properties with large Stokes shift (ca 9000 cm−1 and 6000 cm−1, respectively) and moderate quantum yields (0.11–0.41), both are connected with the presence of inter and intramolecular hydrogen bonds.

Stability of the Monoelectronic Reduction Product from 1,2,5‐Thiadiazole S,S‐Dioxides. Electrochemical, Chemical, and Photoinduced Doping

AbstractThe accumulation of radical anions from 3,4‐disubstituted 1,2,5‐thiadiazole S,S‐dioxides (1) in solution of organic solvents is achieved by electrochemical, chemical and photoinduced pathways. Electrolytic and chemical reduction of 1 produces the radical anions (1•–) in high molar yields (> ca. 80%). The survival of 1•– is measured for ca. three months. The stability of the reduced state depends on its structure and the composition (solvent, reducing agent, and supporting electrolyte) of the medium in which it is generated by the chemical and electrochemical routes. In solution of polar aprotic solvents, 1•– persists even in the presence of water or oxygen. Irradiation with 254 nm light generates 1•– but only in DMF solution; the proposed reaction mechanism involves the participation of the solvent. Radical anions are characterized by cyclic voltammetry, UV‐Vis spectrophotometry and electron spin resonance spectroscopy. The chemical stability and the properties of 1/1•– make them suitable for the development of novel materials for technological applications.