Nonpolar Cosolvent Research Articles

Nonpolar Cosolvent Driving LUMO Energy Evolution of Methyl Acetate Electrolyte to Afford Lithium‐Ion Batteries Operating at −60 °C

AbstractThe operation of lithium‐ion batteries (LIBs) at low temperatures (<−20 °C) is hindered by the low conductivity and high viscosity of conventional carbonate electrolytes. Methyl acetate (MA) has proven to be a competitive low‐temperature electrolyte solvent with low viscosity and low freezing point, but its interfacial stability is poor and remains elusive until now. Here, it is revealed thaat the reductive stability of MA‐based electrolytes is fundamentally governed by the anion‐prevailed solvation structure. Based on this framework, fluorobenzene is employed in the electrolyte to promote the entry of anions into the solvation shell via dipole‐dipole interactions and the generation of free MA, thus enhancing the lowest unoccupied molecular orbital energy of MA. The designed electrolyte enables LiCoO2 (LCO)/graphite cells to exhibit excellent cycling performance at −20 °C (90% retention after 1000 cycles at 1 C) and to remain 91% of their room‐temperature capacity at a super‐low temperature of −60 °C at 0.05 C. Thanks to the plentiful free MA, this electrolyte has a high conductivity (2.61 mS cm−1) at −60 °C and allows LCO/graphite cell to charge at −60 °C. This study offers the possibility of practical applications for those solvents with poor reductive stability and provides new approaches to designing advanced electrolytes for low‐temperature applications.

Dynamics simulation of the effect of cosolvent on the solubility and tackifying behavior of PDMS tackifier in supercritical CO2 fracturing fluid

Due to the low viscosity of supercritical carbon dioxide (SC-CO2) fracturing fluid, the method of adding tackifier is generally chosen to improve its sand carrying ability. Recently, siloxane-based tackifier has been widely utilized because of low cohesive energy and good viscosity building properties, but cosolvents are somehow needed to be added in the system to improve its solubility in SC-CO2. In this study, polydimethylsiloxane (PDMS)- a widely used siloxane polymer- was selected as the object tackifier. First, the effects of the addition of cosolvents such as ethanol, acetic acid, cyclohexane and toluene on dissolution behaviors of PDMS in SC-CO2 fracturing fluid were investigated by molecular dynamics simulation. Moreover, the solubilization effects of polar and nonpolar cosolvents on PDMS in SC-CO2 fracturing fluid were studied by comparing the binding energy, cohesive energy density and radial distribution function between solvent-solvent and between solvent-solute. The simulation results showed that cyclohexane could improve the solubility parameters of SC-CO2 the most at the same cosolvent concentration, and SC-CO2 was more uniformly distributed in the system. Meanwhile, the interactions between toluene and SC-CO2 was the strongest, and SC-CO2 was generally uniformly distributed in the system. However, ethanol and acetic acid performed poorly because they could produce hydrogen bonds with certain directionality and saturation. It was revealed that the mechanism of using cosolvents to improve the solubility of PDMS in SC-CO2 was based on the equilibrium of intermolecular forces between CO2 and PDMS, between CO2 and cosolvent, and between PDMS and cosolvent. When the siloxane-based tackifier was a nonpolar material, cyclohexane was recommended as the cosolvent. If the siloxane-based tackifier itself had some weak polarity, toluene was more suitable.

Promoting solution-phase superlattices of CsPbBr3 nanocrystals.

We present a size-selective method for purifying and isolating perovskite CsPbBr3 nanocrystals (NCs) that preserves their as-synthesized surface chemistry and extremely high photoluminescence quantum yields (PLQYs). The isolation procedure is based on the stepwise evaporation of nonpolar co-solvents with high vapor pressure to promote precipitation of a size-selected product. As the sample fractions become more uniform in size, we observe that the NCs self-assemble into colloidally stable, solution-phase superlattices (SLs). Small angle X-ray scattering (SAXS) and dynamic light scattering (DLS) studies show that the solution-phase SLs contain 1000s of NCs per supercrystal in a simple cubic, face-to-face packing arrangement. The SLs also display systematically faster radiative decay dynamics and improved PLQYs, as well as unique spectral absorption features likely resulting from inter-particle electronic coupling effects. This study is the first demonstration of solution-phase CsPbBr3 SLs and highlights their potential for achieving collective optoelectronic phenomena previously observed from solid-state assemblies.

Water-Based Dynamic Depsipeptide Chemistry: Building Block Recycling and Oligomer Distribution Control Using Hydration-Dehydration Cycles.

The high kinetic barrier to amide bond formation has historically placed narrow constraints on its utility in reversible chemistry applications. Slow kinetics has limited the use of amides for the generation of diverse combinatorial libraries and selection of target molecules. Current strategies for peptide-based dynamic chemistries require the use of nonpolar co-solvents or catalysts or the incorporation of functional groups that facilitate dynamic chemistry between peptides. In light of these limitations, we explored the use of depsipeptides: biorelevant copolymers of amino and hydroxy acids that would circumvent the challenges associated with dynamic peptide chemistry. Here, we describe a model system of N-(α-hydroxyacyl)-amino acid building blocks that reversibly polymerize to form depsipeptides when subjected to two-step evaporation–rehydration cycling under moderate conditions. The hydroxyl groups of these units allow for dynamic ester chemistry between short peptide segments through unmodified carboxyl termini. Selective recycling of building blocks is achieved by exploiting the differential hydrolytic lifetimes of depsipeptide amide and ester bonds, which we show are controllable by adjusting the solution pH, temperature, and time as well as the building blocks’ side chains. We demonstrate that the polymerization and breakdown of the depsipeptides are facilitated by cyclic morpholinedione intermediates, and further show how structural properties dictate half-lives and product oligomer distributions using multifunctional building blocks. These results establish a cyclic mode of ester-based reversible depsipeptide formation that temporally separates the polymerization and depolymerization steps for the building blocks and may have implications for prebiotic polymer chemical evolution.

Coordination Engineering of Single‐Crystal Precursor for Phase Control in Ruddlesden–Popper Perovskite Solar Cells

Abstract2D Ruddlesden–Popper perovskites (RPPs) have recently drawn significant attention because of their structural variability that can be used to tailor optoelectronic properties and improve the stability of derived photovoltaic devices. However, charge separation and transport in 2D perovskite solar cells (PSCs) suffer from quantum well barriers formed during the processing of perovskites. It is extremely difficult to manage phase distributions in 2D perovskites made from the stoichiometric mixtures of precursor solutions. Herein, a generally applicable guideline is demonstrated for precisely controlling phase purity and arrangement in RPP films. By visually presenting the critical colloidal formation of the single‐crystal precursor solution, coordination engineering is conducted with a rationally selected cosolvent to tune the colloidal properties. In nonpolar cosolvent media, the derived colloidal template enables RPP crystals to preferentially grow along the vertically ordered alignment with a narrow phase variation around a target value, resulting in efficient charge transport and extraction. As a result, a record‐high power conversion efficiency (PCE) of 14.68% is demonstrated for a (TEA)2(MA)2Pb3I10 (n = 3) photovoltaic device with negligible hysteresis. Remarkably, superior stability is achieved with 93% retainment of the initial efficiency after 500 h of unencapsulated operation in ambient air conditions.

Controlling nucleation and growth of nano-CaCO3 via CO2 sequestration by a calcium alkoxide solution to produce nanocomposites for drug delivery applications

The proposed sol-gel synthesis of CaCO3 proved to create unprecedented size of CaCO3 nanoparticles with striking size uniformity. The obtained results clearly demonstrate their ability to incorporate hydrophobic components in a nanocomposite matrix converting them into amorphous nano sized particles, building stable colloids via release in acidic medium. Transfer of a sol produced in organic medium into water in the presence of albumen surfactant results in relatively uniform micro particles about 1μm size. The obtained materials show characteristics attractive for use in drug delivery and potentially also a variety of other industrial applications.

Continuous hydrothermal liquefaction of macroalgae in the presence of organic co-solvents

This paper examines the use of organic co-solvent (n-heptane, toluene and anisole, up to 10wt.%) in the hydrothermal liquefaction of macroalgal biomass as a means of achieving in situ fractionation of the biocrude product according to polarity. The filamentous freshwater macroalga Oedogonium was grown under nutrient-depleted conditions to achieve a low nitrogen content, 1.1wt.% N. Its hydrothermal liquefaction in a continuous pilot plant reactor (300–350°C, 3–5min and 2–5wt.% loadings) yielded up to 25wt.% (dry ash-free basis, daf) extractable biocrude. More severe conditions led to biocrudes in higher yields, with reduced oxygen and slightly increased nitrogen contents, and with lower viscosity. The presence of co-solvents had little effect on the total biocrude yield but gave rise to in situ separation of the biocrude into distinct fractions associated with the organic phase (designated solvent oil) and the aqueous phase (designated DCM oil). The amount of solvent oil produced exceeded the amount that could be extracted at room temperature, by that solvent, from the product mixture obtained in the absence of co-solvent. The relative proportions and properties of the solvent and DCM fractions varied with the polarity of the co-solvent. Anisole co-solvent dissolved nearly all the biocrude and the resulting viscous oil was similar to that obtained without co-solvent. On the other hand, solvent oil produced with n-heptane (~7.4wt.% daf yield, or ~37% of the total biocrude) had significantly reduced levels of nitrogen (1.1wt.%) and oxygen (12.5wt.%) and possessed relatively low viscosity. Toluene co-solvent HTL produced a solvent oil with intermediate yield and properties. Co-solvent HTL offers a simple and effective means of fractionating HTL biocrude on the basis of polarity. A non-polar co-solvent such as n-heptane produces an enhanced product fraction more suitable for hydrotreating than the mixed product obtained without co-solvent.

Permselectivity of cation-exchange membranes between different cations in aqueous alcohol mixtures

In view of the separation and purification of salt streams, the permselectivity of ion-exchange membranes between different counter-ions is of interest. This paper investigates the permselectivity of two cation-exchange membranes (Neosepta CMS and Neosepta CMX). The separation between either sodium/calcium, sodium/protons or calcium/protons was studied and the influence of operating parameters was tested. It was found that a change in concentration ratio did not have a significant effect on the permselectivity. Furthermore, the monovalent selective membrane enables the preferential removal of sodium in an excess amount of calcium. The separation of sodium or calcium from protons is hampered because of the high mobility of protons in aqueous solutions. In the presence of weak bases, such as acetate and formate, the permselectivity (Na+ relative to H+) is increased more than 100 times. As a solvent either water or a solvent mixture of water with methanol or ethanol was used. Generally, the permselectivity changed according to the variation in ion mobility in the solvent mixture. The permselectivity between sodium and protons was enhanced, while the permselectivity between sodium and calcium was decreased. Hereby, the more nonpolar co-solvent, ethanol, has a larger influence than methanol.

Prediction of cosolvent effect on solvation free energies and solubilities of organic compounds in supercritical carbon dioxide based on fully atomistic molecular simulations.

The solubility of organic compounds in supercritical fluids can be dramatically affected by addition of a suitable cosolvent (entrainer) at small concentrations. This makes the screening of the best-suited cosolvent an important task for the supercritical technology. The present study aims to improve our fundamental understanding of solvation in supercritical CO2 with cosolvents. We address the following questions: (1) How does the solvation free energy depend on the chemical class of an organic solute and the chemical nature of co-solvents? (2) Which intermolecular interactions determine the effect of a cosolvent on the solubility of organic compounds? We performed extensive calculations of solvation free energies of monofunctional organic molecules at infinite dilution in supercritical media by the Bennett's acceptance ratio method based on fully atomistic molecular dynamics sampling. Sixteen monofunctional organic molecules were solvated in pure sc-CO2 and sc-CO2 with addition of 6 molar % of cosolvents of different chemical nature: ethanol, acetone, and n-hexane. Cosolvent-induced solubility enhancement (CISE) factors were also calculated. It was found that formation of significant number of hydrogen bonds between a solute and cosolvent molecules leads to a profound solubility enhancement. The cosolvent effect is proportional to the number of hydrogen bonds. When polar cosolvents do not form hydrogen bonds with solutes, the CISE correlates with the dipole moment of solute molecules. However, the electrostatic interactions have a small impact on the solubility enhancement compared to hydrogen bonding. Addition of a nonpolar cosolvent, n-hexane, has a very little effect on the solvation Gibbs free energy of studied small organic molecules. The observed trends were discussed in line with available experimental data.

Competitive role of structural properties of titania–silica mixed oxides and a mechanistic study of the photocatalytic degradation of phenol

TiO2–SiO2 mixed oxide materials were hydrothermally synthesized and the photocatalytic degradation of phenol under UV-irradiation was evaluated. We also demonstrated that varying the co-solvent, modulates the structural properties of the materials. In particular, the use of non-polar co-solvents such as toluene seemed to increase the crystallinity, surface area, and pore diameter while the crystallite size of titania seemed to change little. A comprehensive characterization using surface and bulk techniques evidenced the role of porosities, crystallinity, and Ti–O–Si linkages of the mixed oxides as significant factors that contribute to the degradation of phenol. The TiO2–SiO2 mixed oxide material prepared using only ethanol as the solvent showed 24% degradation of phenol after 120min of irradiation whereas other mixed oxide materials degraded phenol more efficiently (57% to 100%) in the same duration of time. The higher photocatalytic activities of the mixed oxide materials prepared using non-polar solvents is attributed to a combination of factors that include higher Apparent Surface Coverages of Ti–O–Si heterolinkages, larger pore sizes, and most importantly higher crystallinities of the titania phase. Larger pore sizes enabled better transport of reactant molecules and products to and from the active sites (Ti–O–Si heterolinkages) and the higher crystallinities of the titania phase helped in minimizing the electron–hole recombination in these photocatalysts, and thus resulted in high degradation efficiencies.

Biodiesel production by transesterification of sludge in supercritical conditions

In this study wastewater treatment plant (WWTP) sludge was subjected to a reactive pyrolysis treatment to produce a high quality pyro-oil. Sludge was treated in supercritical conditions in the presence of methanol using hexane as cosolvent in a high pressure lab-autoclave. The variables affecting the pyro-oil yield and the product quality, such as mass ratio of alcohol to sludge, presence of cosolvent and temperature, were investigated. It was found that the use of a non-polar cosolvent (hexane) presents advantages in the production of high quality pyro-oil from sludge: increase of the non-polar pyro-oil yield and a considerable reduction of the amount of methanol needed to carry out the transesterification of fatty acids present in the sludge.

Steady-state and time-resolved fluorescence behavior of coumarin-153 in a hydrophobic ionic liquid and ionic liquid–toluene mixture

Steady-state and time-resolved fluorescence behavior of C-153 in neat ultra hydrophobic 1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and its mixture with toluene has been investigated. Steady-state absorption and emission spectral behavior of C-153 is found not to be affected by the nonpolar cosolvent. Time-resolved fluorescence anisotropy measurements show that the rotational diffusion of the probe becomes faster in presence of toluene. Solvation dynamics in ionic liquid–toluene mixtures is found to be biphasic, and the average solvation time is found to decrease with the addition of nonpolar cosolvent to the ionic liquid. A significant blue shift of the time-zero maximum of fluorescence spectrum upon addition of toluene indicates a more nonpolar environment around C-153 at the initial stage of dynamics in the mixed solvent system. A comparison of the dynamics of solvation data in ionic liquid and ionic liquid–toluene mixture suggests that toluene can effectively penetrate into the ionic liquid-rich cybotactic region of the probe. This is explained in terms of favorable hydrophobic interaction between ionic liquid and toluene.

Solubility of solid solutes in supercritical carbon dioxide with and without cosolvents

The solubility of 2-naphthol and anthracene in supercritical CO 2 was determined at 308.1, 318.1 and 328.1 K, with and without cosolvent. The influence of three polar or nonpolar cosolvents, acetone, ethanol and cyclohexane, was studied at concentrations of 3.6 and 4.0 mol%. The solubility enhancement with these cosolvents is considerable, and the cosolvent effect increases in the order ethanol, acetone, and cyclohexane for 2-naphthol and for anthracene, the order is cyclohexane, ethanol, and acetone. The influence of density and cosolvent on the solid solubility was studied and discussed.

분말사출성형에서 초임계유체를 이용한 탈지공정

The purpose of the present study is to investigate the method decreasing debinding time as well as lowering operation condition than pure supercritical <TEX>$CO_2$</TEX> debinding by using cosolvent or binary mixture of propane + <TEX>$CO_2$</TEX>. First method is to add cosolvent, such as n-hexane, DCM, methanol, 1-butanol, in supercritical <TEX>$CO_2$</TEX>. In case of adding cosolvent, we were found the addition of non-polar cosolvent (n-hexane) improves dramatically the binder removal rate (more than 2 times) compared with pure supercritical <TEX>$CO_2$</TEX> debinding, second method is to use mixture of supercritical propane + <TEX>$CO_2$</TEX>, as solvent. In case of using mixture of supercritical propane + <TEX>$CO_2$</TEX>, the rate of debinding speeded up with increasing of pressure and concentration of propane at 348.15 K. It was found that addition of cosolvent (e.g., n-hexane, DCM) and binary mixture propane + <TEX>$CO_2$</TEX> for supercritical solvent remarkably improved binder removal rate for the paraffin wax-based binder system, in comparison with using pure supercritical <TEX>$CO_2$</TEX>.

Supercritical Carbon Dioxide debinding in metal injection molding (MIM) process

The conventional debinding process in metal injection molding (MIM) is critical, environmentally unfriendly and time consuming. On the other hand, supercritical debinding is thought to be an effective method appropriate for eliminating the aforementioned inconvenience in the prior art. In this paper, supercritical debinding is compared with the conventional wicking debinding process. The binder removal rates in supercritical CO2 have been measured at 333.15 K, 348.15 K, and 358.15 K in the pressure range from 20 MPa to 28 MPa. After sintering, the surface of the silver bodies were observed by using SEM. When the supercritical CO2 debinding was carried out at 348.15 K, all the paraffin wax (71 wt% of binder mixture) was removed in 2 hours under 28 MPa and in 2.5 hours under 25 MPa. We also studied the cosolvent effects on the binder removal rate in the supercritical CO2 debinding. It was found that the addition of non-polar cosolvent (n-hexane) dramatically improves the binder removal rate (more than 2 times) for the paraffin wax-based binder system.

Evaluation of Co-solvents with supercritical fluid extraction of atrazine from soil.

Supercritical fluid extraction (SFE) with CO(2) has been successfully applied to herbicide extractions from soil. The objectives of this work were to compare extraction efficiency of atrazine from soil using different types and quantities of co-solvent modifiers under a specified set of SFE instrument conditions and to determine the ruggedness of an optimized extraction program and co-solvent on several soils with varying characteristics. The effect of 18 co-solvents on atrazine extraction from Lufkin fine sandy loam was determined using a completely randomized design with six replications. Extractions of Lufkin soil using the more nonpolar co-solvents had recovery similar to extractions where no co-solvent was added. The co-solvents that showed high extraction efficiency, low incidences of restrictor plugging, and ease of cleaning extraction cells were acetone, acetone:water mixtures (with and without 1% triethylamine), and acetonitrile. The addition of 1% triethylamine (TEA) did not increase recovery significantly. The 9:1 acetone:water mixture with 1% TEA was used for the soil comparison because of the high atrazine recovery and low water content. No differences in atrazine recovery were detected between extractions of the four representative soils when the same extraction conditions were employed. No cleanup steps were included in the procedure, yet adequate chromatography results were obtained suggesting some selectivity for this procedure. These data indicate that SFE with optimized conditions and appropriate co-solvents is a relatively robust method that can effectively be used in soil extractions of atrazine.

98/03101 Yields of oil products from thermochemical biomass conversion processes

This paper examines the use of organic co-solvent (n-heptane, toluene and anisole, up to 10 wt.%) in the hydrothermal liquefaction of macroalgal biomass as a means of achieving in situ fractionation of the biocrude product according to polarity. The filamentous freshwater macroalga Oedogonium was grown under nutrient-depleted conditions to achieve a low nitrogen content, 1.1 wt.% N. Its hydrothermal liquefaction in a continuous pilot plant reactor (300–350 °C, 3–5 min and 2–5 wt.% loadings) yielded up to 25 wt.% (dry ash-free basis, daf) extractable biocrude. More severe conditions led to biocrudes in higher yields, with reduced oxygen and slightly increased nitrogen contents, and with lower viscosity. The presence of co-solvents had little effect on the total biocrude yield but gave rise to in situ separation of the biocrude into distinct fractions associated with the organic phase (designated solvent oil) and the aqueous phase (designated DCM oil). The amount of solvent oil produced exceeded the amount that could be extracted at room temperature, by that solvent, from the product mixture obtained in the absence of co-solvent. The relative proportions and properties of the solvent and DCM fractions varied with the polarity of the co-solvent. Anisole co-solvent dissolved nearly all the biocrude and the resulting viscous oil was similar to that obtained without co-solvent. On the other hand, solvent oil produced with n-heptane (~ 7.4 wt.% daf yield, or ~ 37% of the total biocrude) had significantly reduced levels of nitrogen (1.1 wt.%) and oxygen (12.5 wt.%) and possessed relatively low viscosity. Toluene co-solvent HTL produced a solvent oil with intermediate yield and properties. Co-solvent HTL offers a simple and effective means of fractionating HTL biocrude on the basis of polarity. A non-polar co-solvent such as n-heptane produces an enhanced product fraction more suitable for hydrotreating than the mixed product obtained without co-solvent.

Effects of the co-solvent energy parameter and dipolar strength on solute residual chemical potential

We investigate the effects of size and energy parameters and dipole moment of co-solvent molecules on the solute residual chemical potential in infinitely dilute supercritical fluids. To determine the chemical potential, an NPT test-particle computer simulation method is employed. Both polar and nonpolar co-solvent are considered. The results show that the Lennard-Jones (LJ) energy parameter of the co-solvent greatly affects the solubility of the solute whereas the size parameter does not. For the system containing polar co-solvent and polar solute, we find that a larger co-solvent dipole moment enhances the solute solubility. By comparing the solute chemical potential reduction due to the long range dipole-dipole interaction with that due to the short range LJ interaction, we also find that the local molecular interaction dominates the value of the solute residual chemical potential.

Solvatochromic study on nitroanilines. Preferential solvation vs dielectric enrichment in binary solvent mixtures

The preferential solvation approach and the dielectric enrichment model have been applied to explain the solvatochromic behavior of o -, m - and p -nitroaniline ( o NA, m NA and p NA) in several binary solvent mixtures. Cyclohexane was used as the “inert” nonpolar cosolvent in every mixture. The other solvents were chosen trying to vary their polarity as much as possible as well as their hydrogen bond donor or acceptor capabilities. Preferential solvation is detected in every solvent mixture studied. These global interactions were quantified by calculating the preferential solvation constant, K . Also, by using the previously developed model, we calculated for each pair of solvent mixtures a theoretical curve and the corresponding K D due to dielectric enrichment. Non hydrogen bond acceptor solvents (β=0), give values of K quite similar to those of K D , indicating that the preferential interaction is practically dielectric in nature. When the interacting solvent is a hydrogen bond acceptor, the values of K are higher than K D according to the acidity of the H in the amino group in the solutes. The values of K as well as of K D for any solvent mixtures in general follow the order p NA > m NA > o NA as expected, considering the values of μ g and μ g -μ ex . Studies in pure solvent support previous conclusions.

Dielectric enrichment in binary solvent mixtures. The intramolecular hydrogen bond in N-alkyl-substituted o-nitroanilines. Substituent effects

In this work we report solvatochromism studies on o-nitroaniline and several N-alkyl-o-nitroaniline derivatives used as solutes in solvent mixtures of an "inert" nonpolar cosolvent, cyclohexane, and THF as a solvent with hydrogen bond acceptor ability. These studies allowed us to establish the competition between inter- and intramolecular hydrogen bond in solutes. This was done by comparing the magnitude of the local inhomogeneity induced by the solute-in-solvent mixture, that is, "preferential solvation," using Suppan's dielectric enrichment model as modified by us to be applied to electronic transitions. Since preferential solvation accounts for dielectric as well as specific interactions while dielectric enrichment only for the former, it was shown by comparison that it is possible to separate both effects and even quantify them. It was deduced that N-alkyl-o-nitroanilines form a strong intramolecular hydrogen bond, which remains unbroken even in polar solvents and hydrogen bond acceptors such as dimethyl sulfoxide. This was also confirmed by solvatochromic studies in pure solvents. On the other hand, a symmetrical dependence of the effects of alkyl substituents and solvents on the shifts of the absorption spectra was observed.