Water Miscibility Research Articles

H_2-H_2O demixing in Uranus and Neptune: Adiabatic structure models

Demixing properties of major planetary constituents influence the interior structure and evolution of planets. Comparing experimental and computational data on the miscibility of hydrogen and water to adiabatic profiles suggests that phase separation between these two components occurs in the ice giants Uranus and Neptune. We aim to predict the atmospheric water abundance and transition pressure between the water-poor outer envelope and the water-rich deep interior in Uranus and Neptune. We constructed seven H$_ $-H$_ $O phase diagrams from the available experimental and computational data. We computed interior adiabatic structure models and compared these to the phase diagrams to infer whether demixing occurred. We obtain a strong water depletion in the top layer due to the rain-out of water and find upper limits on the atmospheric water-mass fraction Zatm of 0.21 for Uranus and 0.16 for Neptune. The transition from the water-poor to the water-rich layer is sharp and occurs at pressures $P_Z$ between 4 and 11 GPa. Using these constraints on Zatm and $P_Z$, we find that the observed gravitational harmonics $J_2$ and $J_4$ can be reproduced if $P_Z 10$ GPa in Uranus and $ 5$ GPa in Neptune, and if the deep interior has a high primordial water-mass fraction of 0.8, unless rocks are also present. The agreement with $J_4$ is improved if rocks are confined deeper than $P_Z$, for instance, below a rock cloud level at 2000 K (20--30 GPa). These findings confirm classical few-layer models and suggest that a layered structure may result from a combination of primordial mass accretion and subsequent phase separation. Reduced observational uncertainty in $J_4$ and its dynamic contribution, atmospheric water abundance measurements from the Uranus Orbiter and Probe (UOP) or a Neptune mission, and better understanding of the mixing behaviour of constituents are needed to constrain the interiors of ice giants.

Potential toxic effects linked to taurine interactions with alkanolamines and diisopropylamine

Diisopropylamine (DIPA), aminomethyl propanol (AMP), amino ethoxy ethanol (AEE), diethanolamine (DEA), ethanolamine (EA), pyridine (PYR) and methyl diethanolamine (MDEA) are used for carbon capture and to sweeten sour gas, and are found in groundwater. They are also used in cosmetic products. Taurine is abundant in the body, with key biological functions linked to its charged SO groups. Interactions between SO and amines have not been studied, but can strongly affect the biological function of taurine. Fourier transform infrared spectroscopy indicates SO…HN hydrogen bonding between taurine and DIPA, AMP, AEE, DEA, EA and MDEA. These interactions induce the formation of hydrophobic amine-taurine clusters, thus decreasing amine miscibility in water, as revealed by light scattering. This effect is most marked for DIPA, leading to turbid mixtures indicative of micron-sized droplets. PYR and taurine likely interact via S…N bonding. This study offers insights regarding potential mechanisms of amine toxicity to humans.Graphical

Preparation of high-performance PVDF hollow fiber microporous membranes via the c-TIPS process with water-insoluble solvent as the second solvent

Triethyl phosphate (TEP) is a promising solvent for the c-TIPS process given its high boiling point and water miscibility. However, casting solutions containing high TEP concentration generally trigger gelation, giving a dense outer surface in PVDF membrane. In this work, we fabricated PVDF hollow fiber membranes with a porous outer surface and excellent mechanical strength via a complex thermally induced phase separation (c-TIPS) method and applied them in the DCMD process. A water-insoluble solvent, dibasic ester solvents (DBEs), was used as the second solvent to modulate the phase separation process of the PVDF/TEP system. The mass transfer between the coagulation bath and the DBEs solvent was analyzed. It could decrease the polymer-solvent interactions and the rate of solvent efflux in the coagulation bath, contributing to the development of a porous membrane structure. When the weight ratio of TEP/DMA was 1, the optimized PVDF hollow fiber membrane exhibited a tensile strength of 8.34 MPa, an average pore diameter of 0.14 μm, giving the permeate flux of 18.56 ± 2.5 kg m−2 h−1 in DCMD and excellent operational stability when subjected to high brine concentration. Thus, the fabrication method shows a promising potential for tailoring the surface porosity and bulk structure. The PVDF membranes developed in this study demonstrate potential for use in membrane distillation and related applications.

Unraveling the Surface Activity of Ethanol-Water Mixtures through Experiments and Molecular Dynamics Simulations.

Ethanol's complete miscibility in water makes it a widely used solvent in various applications, such as organic compound synthesis, paint manufacture, chromatography, and cosmetics preservation. Studies suggest that ethanol's concentration at interfaces can be higher than in the bulk due to its amphiphilic nature, especially at lower concentrations, making it a surface-active agent. Accordingly, ethanol plays a crucial role in controlling the emulsion stability, foam formation, heat transfer, and coating adhesion. However, the precise concentration ranges up to which ethanol's surface activity dominates its interfacial properties, and the underlying molecular mechanism is not fully understood in the literature. In this context, our foamability experiments, coupled with film stability experiments conducted via ethanol drop impact on varying concentration ethanol-water mixture pools, indicate that the surface-active nature of ethanol is observed up to a maximum of 10% molar ethanol concentration in water. We next employ all-atom molecular dynamics simulations to reveal that the surface tension and other interfacial properties are most significantly affected only up to the molar concentration in the range of 0-10% of ethanol in water. This observation is further supported by free energy analyses, indicating that the stabilization free energy of an ethanol molecule at the interface becomes comparable to that in the bulk region beyond this concentration range. The transition from surface-active to a behavior resembling a homogeneous solution occurs when the molar concentration of ethanol in water exceeds 10%. This transition is attributed to distinctive alterations in the number and strength of ethanol-water hydrogen bonds. These findings provide valuable insights into the interfacial molecular structure, which can be suitably exploited to modulate interfacial properties and dynamic behavior in a wide array of industrial and scientific applications.

Mechanochemical Synthesis of Praziquantel Hemihydrate in the Presence of Five Solvents with Different Water Miscibility

Mechanochemical Synthesis of Praziquantel Hemihydrate in the Presence of Five Solvents with Different Water Miscibility

Microemulsion containing guava leaves essential oil: Enhanced anti-inflammatory, anti-oxidation, anti-tyrosinase activities and skin permeation

In this study, a microemulsion system containing guava leaf essential oil (GLE) was developed to enhance water miscibility, stability and bioactivity. The major chemical components of GLE, d-limonene, and β-caryophyllene, were identified by GC-MS analysis. The microemulsion system consisted of Tween 80 and propylene glycol as the surfactant (S) and co-surfactant (Co–S), respectively, with GLE serving as the oil phase. Three pseudo-ternary phase diagrams were constructed with different S:Co–S ratios (Km) at 2:1, 1:1, and 1:2 to illustrate the microemulsion area. Characterization of GLE contained microemulsions (GLEMEs) was performed using dynamic light scattering (DLS), viscometry, and conductivity measurements. The particle sizes of GLEMEs ranged from 10 to 150 nm. Selected GLEMEs exhibited stable particle sizes for more than 90 days and remained stable over a wide pH range. Additionally, compared to free GLE, these microemulsions demonstrated enhanced anti-tyrosinase and antioxidant activity, as well as improved anti-inflammatory properties. Moreover, microemulsions with high oil content exhibited deeper skin penetration compared to free GLE, while those with high water content accumulated in the upper skin layer.

Effective removal of personal care product residues from aqueous media using hydrophobic deep eutectic solvents: Experimental and computational approach

Personal care product (PCP) residues - classified under micropollutants (MPs)- are widely found in aquatic environments, posing trace-level toxicity. Traditional water treatment techniques struggle to remove these toxins effectively. Deep eutectic solvents (DESs), the liquid mixtures typically composed of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs), have recently emerged as a viable alternative for extracting pollutants from water. Among DESs, hydrophobic deep eutectic solvents (HDESs) exhibit low water miscibility and unique solvent properties. The main objective of this study is to synthesize HDESs to effectively eliminate 2-naphthol and methylparaben- two of the significant chemical contaminants in PCPs- from aqueous media. HDESs were prepared by mixing different terpenes (menthol and thymol) and long-chain carboxylic acids at varying molar ratios. They were characterized using different spectroscopic and thermal techniques. The density and viscosity of the pure DESs were measured as afunction of temperature. Experimental studies were carried out using the liquid–liquid extraction (LLE) method, and the factors influencing the efficiency of extraction were optimized.Considering the limited number of studies on the extraction mechanism of MPs from aqueous media, this study employs comprehensive computational methods, including density functional theory (DFT) and the COnductor-like Screening MOdel for Real Solvents (COSMO-RS), to provide a detailed interpretation of the extraction mechanism. A series of successive extractions were conducted to reduce the DES usage to ensure economic viability. The reusability of the best-performed DES was explored. Additionally, the regeneration of one of the DESs was accomplished through activated carbon-based recovery.---------------------------------------------------------------------------------------------------------------------

Natural deep eutectic solvents as sustainable alternative for the Ultrasound-Assisted extraction of triazines from agricultural soils

Natural deep eutectic solvents (NADES) have gained much attention as a viable and sustainable alternative to traditional organic solvents in multiple areas of analytical chemistry, including extraction of contaminants from samples of environmental concern. In this work, a total of 68 potential NADES have been assayed and further evaluated as sustainable solvents in the development of an ultrasound (US)-assisted extraction method for triazinic herbicides from agricultural soil samples and final determination by HPLC-UV. Choline chloride (ChCl) was used as hydrogen bond acceptor (HBA), and different carboxylic acids, alcohols and amines were tested as hydrogen bond donors (HBDs) in different molar ratios in order to find the optimum combination able to form appropriated NADES for the extraction of triazines. Among the different ChCl:carboxylic acids mixtures tested, those consisting of ChCl:formic acid and ChCl:acetic acid, both in a molar ratio 1:2, presented the better physico-chemical properties (pH, stability at room temperature, water miscibility, etc.). Concerning amines, NADES could not be obtained at any of the combination assayed whereas, among the alcohols tested, 2,3-butanediol was found to be the most appropriated for NADES formation. A three-level factorial design was then used to further evaluate the effect of time and temperature on the ability of these selected optimum NADES for the US-assisted extraction of triazines from agricultural soil samples. Under optimal conditions, the developed US-assisted extraction method provided quantitative recoveries (from 87 to 104 %) with good reproducibility (RSDs lower than 12 %) and limits of detection (LODs) lower than 0.05 μg g−1 for all target triazines.

Dimethyl carbonate as a green alternative to acetonitrile in reversed-phase liquid chromatography. Part I: Separation of small molecules

Nowadays, environmental problems are drawing the attention of governments and international organisations, which are therefore encouraging the transition to green industrial processes and approaches. In this context, chemists can help indicate a suitable direction. Beside the efforts focused on greening synthetic approaches, currently also analytical techniques and separations are under observation, especially those employing large volumes of organic solvents, such as reversed-phase liquid chromatography (RPLC). Acetonitrile has always been considered the best performing organic modifier for RPLC applications, due to its chemical features (complete miscibility in water, UV transparency, low viscosity etc); nevertheless, it suffers of severe shortcomings, and most importantly, it does not fully comply with Environmental, Health and Safety (EHS) requirements. For these reasons, alternative greener solvents are being investigated, especially easily available alcohols.In this work, chromatographic performance of the most common solvents used in reversed-phase chromatography, i.e., acetonitrile, ethanol and isopropanol, have been compared to a scarcely used solvent, dimethyl carbonate (DMC). The analytes of interest were two small molecules, caffeine and paracetamol, whose kinetics and retention behaviour obtained with the four solvents have been compared, and all contributions to band broadening have been assessed. Results about kinetic performance are very promising, indicating that a small amount (7 % v/v) of DMC is able to produce the same efficiency as a 2.5-times larger ACN volume (18 % v/v), and larger efficiency than alcohols.This paper reports, for the first time, fundamental studies concerning the mass transfer phenomena when DMC is used as an organic solvent in RPLC, and, together with the companion paper, represents the results of a research whose final aim was to discover whether DMC is suitable for chromatographic applications both in linear and preparative conditions.

Effects of intramolecular chain conformation on the hydration and miscibility of polyethylene glycol in water studied by means of polymer reference interaction site model theory.

To examine the conventional idea that the gauche conformation of the OCCO dihedral angle promotes the dissolution of polyethylene glycol (PEG) in water through strong hydration, the thermodynamic properties of liquid mixtures of PEG and water were studied by means of polymer reference interaction site model (PRISM) theory. The intramolecular correlation functions required as input for PRISM theory were calculated by the generator matrix method, accompanied by changes in the distribution of dihedral angles. In the infinite dilution limit, the increased probability of gauche conformation of the OCCO dihedral angles stabilizes the hydration of PEG through enhanced hydrogen bonding between the ether oxygen of PEG and water. The mixing Gibbs energies of the liquid mixtures were also calculated in the whole concentration range based on the Gibbs-Duhem equation, as per our recent proposal. A liquid-liquid phase separation was observed when all the dihedral angles of PEG were in the trans conformation; for the liquid mixture to be miscible in the whole concentration range, the introduction of the OCCO gauche conformation was found to be indispensable. The above theoretical results support the conventional idea that the OCCO gauche conformation is important for the high miscibility of PEG and water.

Stretchable and Biocompatible Transparent Electrodes for Multimodal Biosignal Sensing from Exposed Skin

AbstractReal‐time health monitoring technology in daily life requires mechanically robust and transparent electrodes for multimodal biosignal sensing from exposed human epidermis. Here, highly stretchable transparent electrodes comprising a water‐dispersed conductive polymer, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and a protic ionic liquid (IL), 3‐methylimidazolium:bis(trifluoromethylsulfonyl)amide (p‐MIM:TFSI) are reported. Owing to the high water miscibility of p‐MIM:TFSI and its favorable ion exchange capability with PEDOT:PSS, PEDOT:PSS/p‐MIM:TFSI transparent electrodes show enhanced electrical conductivity (σ = 450 S cm−1) and thin‐film stretchability represented by crack onset strain (εc) exceeding 50%. These electrodes outperform other PEDOT:PSS electrodes processed with an aprotic counterpart, 1‐ethyl‐3‐methylimidazolium(EMIM):TFSI, or a traditional ionic salt, Li:TFSI. The PEDOT:PSS/p‐MIM:TFSI thin‐film electrodes are also biocompatible and conformally adhere to human skin; therefore, multimodal biosignals including electrocardiogram, electrooculogram, and electromyogram with high signal‐to‐noise ratios from exposed epidermis on human faces and arms under various measurement conditions mimicking daily activities are collected. Considering the importance of light penetration through human skin for stable biological activity during biosignal monitoring, the results can broaden the applicability of daily‐use wearable biosignal sensors by applying them to exposed human skin.

Arundo donax L Processing in Catalyzed Butanol-Water Media in the Scope of Lignocellulose Biorefineries.

Arundo donax L samples, before or after aqueous extraction to remove extractives, were subjected to chemical fractionation in H2SO4-catalyzed mixtures of 1-butanol and water. The partial miscibility of 1-butanol and water at room temperature allowed the separation of the three major feedstock components in separate streams (lignin, accumulated in the 1-butanol-rich phase; hemicellulose-derived products, accumulated in the aqueous acidic phase; and cellulose, present in the solid phase). The effects of selected variables (temperature, catalyst concentration, reaction time and 1-butanol content of the reaction media) on variables measuring the solid recovery yield and the compositions of phases from fractionation were measured. Using water-extracted A. donax L as a substrate, the best operational conditions enabled 93.2% hemicellulose removal and 85.4% delignification with limited cellulose solubilization (15%). The experimental results provided key information to assess the proposed process in the scope of biorefineries.

Sustainability in Drug and Nanoparticle Processing.

The formulation of drugs in poly(lactic-co-glycolic acid) (PLGA) nanoparticles can be accomplished by various methods, with nanoprecipitation and nanoemulsion being among the most commonly used manufacturing techniques to provide access to high-quality nanomaterials with reproducible quality. Current trends turned to sustainability and green concepts leading to a re-thinking of these techniques, particularly as the conventional solvents for the dissolution of the polymer suffer from limitations like hazards for human health and natural environment. This chapter gives an overview about the different excipients used in classical nanoformulations with a special focus on the currently applied organic solvents. As alternatives, the status quo of green, sustainable, and alternative solvents regarding their application, advantages, and limitations will be highlighted as well as the role of physicochemical solvent characteristics like water miscibility, viscosity, and vapor pressure for the selection of the formulation process, and for particle characteristics. New alternative solvents will be introduced for PLGA nanoparticle formation and compared regarding particle characteristics and biological effects as well as for in situ particle formation in a matrix consisting of nanocellulose. Conclusively, new alternative solvents are available that present a significant advancement toward the replacement of organic solvents in PLGA nanoparticle formulations.

Super‐Amphiphilic Na2Ti3O7 Nanofibrous Film Enabling Water–Oil Miscibility (Adv. Mater. Interfaces 32/2022)

Flexible Super-Amphiphilic Film In article number 2201445, Conghu Hu, Licheng Hua, Jianke Dua, and colleagues describe a flexible Na2Ti3O7 (NTO) film composed of numerous nanofibrous into 3D porous nanostructures with super-amphiphilic properties that enable water and oil miscibility. The film has a high absorption capacity for water and poly-alpha-olefin (PAO) up to 32–36 times its weight. The absorption capacity of the NTO film for water-PAO miscibility can keep at ≈ 22 g g−1 after 20 cyclic applications.

Water Miscibility, Surface Tension, Density, and Dynamic Viscosity of Hydrophobic Deep Eutectic Solvents Composed of Capric Acid, Menthol, and Thymol

Deep eutectic solvents (DESs) are rapidly emerging as environmentally benign and viable alternatives not only to common organic solvents but to relatively toxic ionic liquids as well. By judicious selection of the constituents and subsequent variation in their composition, the key physicochemical properties of the DESs can be easily tailored for a specific application. Impact of variation in constituents as well as their composition on important physical properties of natural DESs (NADESs) prepared using a common fatty acid n-decanoic acid (DA) and two naturally occurring monoterpenoids, thymol (Thy) and L(−)-menthol (Men), is assessed. Specifically, water miscibility, surface tension, density, and dynamic viscosity of 17 different DESs of three combinations of constituents, Men:DA, Thy:DA, and Thy:Men in four, four, and nine compositions, respectively, are measured. The water intake by the DESs under ambient conditions varies from 0.6 to 2.7 mol·kg–1 offering a means to gauge their hydrophobicity. Water miscibility is relatively lower for Men:DA DESs and higher for Thy:DA DESs. Surface tension values are within 28.37 mN·m–1 to 31.14 mN·m–1 under ambient conditions; they are higher for the DESs with the Thy constituent and vary systematically with DES composition. The densities of all the DESs are lower than that of water and decrease linearly with increasing temperature. While density does not vary with composition for Men:DA, it is found to increase linearly with an increase in Thy mole fraction for Thy:DA and Thy:Men DESs. The dynamic viscosity of the DESs are relatively lower as compared to the common tetralkylammonium salt- and metal salt-based DESs, and exhibit strong constituent and composition dependence. Rather than the Arrhenius-type expression, the temperature-dependence of the dynamic viscosity better conforms to the Vogel–Fulcher–Tammann (VFT) model with activation energy of the viscous flow varying systematically with the constituent and composition. Reported physical properties and their dependence on constituents/composition of the NADESs will enhance their utility and help establish them as novel alternate media in science and technology.

Super‐Amphiphilic Na2Ti3O7 Nanofibrous Film Enabling Water–Oil Miscibility

AbstractDue to their extraordinary affinity for both water and oil, super‐amphiphilic materials have garnered considerable interest. A Na2Ti3O7 (NTO) film with super‐amphiphilic properties that enable water and oil miscibility is offered. Multiple nanofibrous 3D porous nanostructures compose the super‐amphiphilic NTO layer. Up to 32–36 times its weight, the film has a high absorption capacity for water and poly‐alpha‐olefin (PAO). The average miscibility ratio of water to oil in the film is ≈6:5. The discovery of NTO nanofibrous film's super‐amphiphilic behavior has significant implications for the development of superwetting materials and their potential applications in the oil emulsion purification and catalyst anchoring industries.

Investigation of Alogliptin-Loaded In Situ Gel Implants by 23 Factorial Design with Glycemic Assessment in Rats.

The aim of the study was to design injectable long-acting poly (lactide-co-glycolide) (PLGA)-based in situ gel implants (ISGI) loaded with the anti-diabetic alogliptin. Providing sustained therapeutic exposures and improving the pharmacological responses of alogliptin were targeted for achieving reduced dosing frequency and enhanced treatment outputs. In the preliminary study, physicochemical characteristics of different solvents utilized in ISGI preparation were studied to select a proper solvent possessing satisfactory solubilization capacity, viscosity, water miscibility, and affinity to PLGA. Further, an optimization technique using a 23 factorial design was followed. The blood glucose levels of diabetic rats after a single injection with the optimized formulation were compared with those who received daily oral alogliptin. N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO), as highly water-miscible and low viscous solvents, demonstrated their effectiveness in successful ISGI preparation and controlling the burst alogliptin release. The impact of increasing lactide concentration and PLGA amount on reducing the burst and cumulative alogliptin release was represented. The optimized formulation comprising 312.5 mg of PLGA (65:35) and DMSO manifested a remarkable decrease in the rats’ blood glucose levels throughout the study period in comparison to that of oral alogliptin solution. Meanwhile, long-acting alogliptin-loaded ISGI systems demonstrated their feasibility for treating type 2 diabetes with frequent dosage reduction and patient compliance enhancement.

A Survey of Gasoline Ameliorator, Methyl-Tert-Butyl Ether (MTBE) on Bovine Serum Albumin: A Spectroscopy and Molecular Dynamic Simulation Study.

Methyl-Tert-Butyl Ether (MTBE) as a gasoline modifier is frequently added to fuels and used in plenty of worldwide applications. MTBE biodegradation in groundwater occurs slowly and produces water miscibility; therefore, it causes diverse environmental and human health concerns. The interaction of MTBE with bovine serum albumin (BSA) as a model protein at physiological conditions is investigated to illustrate the possible interactions of MTBE with the body's proteins. Uv-visible, fluorescence, circular dichroism (CD) spectroscopy methods, and molecular modeling were used to analyze the MTBE's effect on BSA structure and dynamics. The constant protein concentration and various MTBE contents were used for possible interactions. The protein structural analysis shows that MTBE binds to BSA via positive enthalpy and entropy via hydrophobic interactions. Molecular docking shows the participation of several amino acids in the MTBE-BSA interaction. The CD spectroscopy results show that the BSA structure was not changed in the MTBE concentrations utilized in the study. Molecular dynamics (MD) simulation results suggest that MTBE can slightly change protein structure in the last 50ns. Comparing experimental and MD simulation results demonstrated that the BSA secondary structure was maintained in the low concentration of the MTBE. The entropy and enthalpy parameters asserted the hydrophobic interaction was the major force in the interaction between the BSA and MTBE.

Disclosing the Potential of Fluorinated Ionic Liquids as Interferon-Alpha 2b Delivery Systems.

Interferon-alpha 2b (IFN-α 2b) is a therapeutic protein used for the treatment of cancer, viral infections, and auto-immune diseases. Its application is hindered by a low bioavailability and instability in the bloodstream, and the search for new strategies for a target delivery and stabilization of IFN-α 2b to improve its therapeutic efficacy is crucial. Fluorinated ionic liquids (FILs) are promising biomaterials that: (i) can form self-assembled structures; (ii) have complete miscibility in water; and (iii) can be designed to have reduced toxicity. The influence of IFN-α 2b in the aggregation behaviour of FILs and the interactions between them were investigated through conductivity and surface tension measurements, and using electron microscopic and spectroscopy techniques to study FILs feasibility as an interferon-alpha 2b delivery system. The results show that the presence of IFN-α 2b influences the aggregation behaviour of FILs and that strong interaction between the two compounds occurs. The protein might not be fully encapsulated by FILs. However, the FIL can be tailored in the future to carry IFN-α 2b by the formation of a conjugate, which prevents the aggregation of this protein. This work constitutes a first step toward the design and development of FIL-based IFN-α 2b delivery systems.

Characterization of polyurea microcapsules synthesized with an isocyanate of low toxicity and eco-friendly esters via microfluidics: Shape, shell thickness, morphology and encapsulation efficiency

There are some studies on the synthesis of polyurea microcapsules. However, there is hardly a case where both green solvents and non-toxic isocyanates are used, especially in microfluidics. In this work, an environmentally friendly chemical system of interfacial polymerization (isocyanate: HDB-LV; solvent: octyl salicylate or dibutyl adipate) is tested for the first time to produce polyurea microcapsules. The size of microcapsules is calibrated at 78 μm by microfluidics to quantitatively analyze the relationships among shell thickness, encapsulation efficiency and isocyanate concentrations. The influences of solvent types and reactant concentrations on the shape, morphology and shell thickness of microcapsules are studied. Esters with low water miscibility and low amine concentrations (lower reaction rate) are crucial for the formation of spherical microcapsules. An ester with high water miscibility can diffuse into the continuous phase during encapsulation, which results in broken microcapsules. A high concentration of amine can probably cause cross-linking not only at the interface but also inside the droplet template, which leads to microcapsule deformation. A linear relationship is observed between the shell thickness of microcapsules and the isocyanate concentration. Overall, a high encapsulation efficiency (more than 90%) for octyl salicylate is achieved with polyurea microcapsules.