Amphiphilic Solvents Research Articles

Pathway Selection in Temporal Evolution of Supramolecular Polymers of Ionic π-Systems: Amphiphilic Organic Solvent Dictates the Fate of Water.

Understanding solvent-solute interactions is essential to designing and synthesising soft materials with tailor-made functions. Although the interaction of the solute with the solvent mixture is more complex than the single solvent medium, solvent mixtures are exciting to unfold several unforeseen phenomena in supramolecular chemistry. Here, we report two unforeseen pathways observed during the hierarchical assembly of cationic perylene diimides (cPDIs) in water and amphiphilic organic solvent (AOS) mixtures. When the aqueous supramolecular polymers (SPs) of cPDIs are injected into AOS, initially kinetically trapped short SPs are formed, which gradually transform into thermodynamically stable high aspect ratio SP networks. Using various experimental and theoretical investigations, we found that this temporal evolution follows two distinct pathways depending on the nature of the water-AOS interactions. If the AOS is isopropanol (IPA), water is released from cPDIs into bulk IPA due to strong hydrogen bonding interactions, which further decreases the monomer concentration of cPDIs (Pathway-1). In the case of dioxane AOS, cPDI monomer concentration further increases as water is retained among cPDIs (Pathway-2) due to relatively weak interactions between dioxane and water. Interestingly, these two pathways are accelerated by external stimuli such as heat and mechanical agitation.

Alkanediol–hexafluoroisopropanol amphiphilic supramolecular solvent: Fabrication, characterization, and application potential for doping control of hormones and metabolic modulators in human urine

A novel amphiphilic supramolecular solvent (SUPRAS) was developed by hexafluoroisopropanol (HFIP)-induced self-assembly of 1,2-hexanediol in an aqueous matrix. Its application potential in multiclass determination was assessed by extracting from urine 10 prohibited hormones and metabolic modulators (log P from 2.38 to 7.57) listed by the World Anti-Doping Agency (WADA). This SUPRAS is stably formed across a wide pH range (2–12) and is unaffected by salt concentrations (<10 % g mL−1 of NaCl), and it has a higher density than water. The dehydration and hydrogen bonding ability of HFIP, as well as hydrophobic interactions between alkanediols, dominates the formation of the SUPRAS. The nanostructure of the SUPRAS, composed of 1,2-hexanediol, HFIP, and a high content of water (>25 %, w/w), forms large spherical micellar aggregates (10–100 μm) that exhibit amphiphilic properties. A 1,2-hexanediol-HFIP SUPRAS-based liquid-phase microextraction (LPME) method for detection of selected prohibited drugs in urine coupled with liquid chromatography–tandem mass spectrometry (LC-MS/MS) was established, optimized, and validated. The method showed fast extraction time (30 s of vortex) and low solvent consumption (160 μL of organic solvent). Under the optimal conditions (7 % g mL−1 of 1,2-hexanediol, 10 % v/v of HFIP), the SUPRAS achieved high extraction efficiencies (>80 %) and an enrichment factor of 6.0, with minimal matrix effects for all analytes due to its high amphiphilicity and large surface area. The method demonstrated excellent linearity (R ≥0.9909), with method limits of detection ranging from 0.018 to 0.18 ng mL−1 and method limits of quantitation ranging from 0.060 to 0.60 ng mL−1, which are well below the minimum required performance levels set by authorities. Furthermore, the intra- and inter-day relative recoveries for spiked human urine samples varied in the ranges of 90.3–121 % and 88.1–119 %, respectively, with relative standard deviations less than 13 % and 19 %, respectively. This SUPRAS-based LPME method proves to be simple, highly efficient, and eco-friendly, and it has promising potential for multiclass determination in doping control.

Enhanced oil recovery for siliciclastic reservoirs using alcoholic micellar solutions: performance evaluation in core flooding systems

Enhanced Oil Recovery (EOR) assumes a fundamental role in augmenting reservoir productivity through chemical methods. The optimal selection of injection fluids becomes pivotal for managing surface and interfacial tension while altering rock wettability to enhance water affinity. This study investigates alcoholic micellar solutions for EOR in siliciclastic reservoirs, utilizing lauryl alcohol surfactant, 1-butanol as an amphiphilic solvent, and distilled water. The characterization of these systems encompassed micellar diameter, conductivity, and surface tension, which validated the micellar structures in these systems. EOR tests achieved a remarkable oil recovery of up to 74% with a mere 10% of active matter. Wettability tests exhibited a crucial contact angle of 27.8° for water, indicating favorable oil displacement conditions. This research unveils the potential of alcoholic micellar solutions in EOR, emphasizing the significance of tailored injection fluids to enhance reservoir management and productivity.

Non-aqueous lyotropic liquid crystalline phases of natural surfactant Withania somnifera for antibacterial applications

Lyotropic liquid crystalline (LLC) phases are derived from a binary mixture of Withania somnifera roots and ethylene glycol. Studied concentrations of Withania somnifera roots/ethylene glycol are 2:98, 5:95, 10:90, 20:80 and 30:70 wt/wt%. The nematic lyotropic phase is obtained for all the concentrations examined under polarising optical microscopy (POM). The formation of a lyotropic phase in these systems could be explained by considering hydrogen bonding between amphiphilic molecules (Withanolides) and solvent (-OH groups). Nematic lyotropic phases are further tested for antibacterial activity against gram-positive (Bacillus subtilis) and gram-negative (Pseudomonas stutzeri) bacteria. The LLCs show strong inhibition of approximately 2-3 times higher than that of the standard antibiotic (Streptomycin) for gram-positive bacteria Bacillus subtilis. It is noted that the concentration of the binary mixture shows a strong effect on the inhibition of the bacteria irrespective of the nematic ordering for both bacteria.

Interfacial Interaction in Colloidal Heteronanostructures of Tb3+-Complex and Eu3+-Doped Nanosheets: Implications for Bioprobes

It is essential for luminescent materials to be compatible with complex bioenvironments when used for probing biological events. Förster resonance energy transfer (FRET) is a common process in gaining enhanced luminescence signals, in which the interaction between the donor and acceptor plays a decisive role in the optical properties of heterostructured bioprobes. Yet systematic investigations on the gradient amphiphilic and electrostatic interaction effect on luminescence in a complex environment are scarce. Heteronanostructures of Tb(C12H8N2)2(NO3)3 nanocrystals and Eu3+-doped oxide nanosheets in various solutions with varied double electric layers and amphiphilic capacities are chosen for the investigation. It is found that a complex redox process takes place and an interfacial Tb–O bond is formed during preparation of the heteronanostructures. According to the decay dynamics of Tb3+ and Eu3+ emission of the heteronanostructures in various amphiphilic alcohol solvents, the interfacial Tb3+ → Eu3+ energy transfer efficiency apparently displays an extraordinary dependence on alkyl chain length after excluding the refractive index effect, while the zeta potential data suggest that the interfacial electrostatic force on the heteronanostructures should be dominant via the electric double layer in alcohol solvents with short alkyl chain. As the length of alkyl chain increases, the amphiphilic force on the heteronanostructures with amphiphilic Tb(phen)2(NO3)3 and hydrophilic Eu3+-doped nanosheets tends to be overwhelming. These competitive forces strengthen the interaction between Tb3+ and Eu3+ and result in enhancement of the interfacial Tb3+ → Eu3+ energy transfer efficiency. The research helps design potential new bioprobes concerning the interfacial interaction in amphiphilic and salty biosystems.

An Amphiphilic Molecule-Regulated Core-Shell-Solvation Electrolyte for Li-Metal Batteries at Ultra-Low Temperature.

Lithium metal batteries hold great promise for promoting energy density and operating at low temperatures, yet they still suffer from insufficient Li compatibility and slow kinetic, especially at ultra-low temperatures. Herein, we rationally design and synthesize a new amphiphilic solvent, 1,1,2,2-tetrafluoro-3-methoxypropane, for use in battery electrolytes. The lithiophilic segment is readily to solvate Li+ to induce self-assembly of the electrolyte solution to form a peculiar core-shell-solvation structure. Such unique solvation structure not only largely improves the ionic conductivity to allow fast Li+ transport and lower the desolvation energy to enable facile desolvation, but also leads to the formation of a highly robust and conductive inorganic SEI. The resulting electrolyte demonstrates high Li efficiency and superior cycling stability from room temperature to -40 °C at high current densities. Meanwhile, anode-free high-voltage cell retains 87 % capacity after 100 cycles.

An Amphiphilic Molecule‐Regulated Core‐Shell‐Solvation Electrolyte for Li‐Metal Batteries at Ultra‐Low Temperature

AbstractLithium metal batteries hold great promise for promoting energy density and operating at low temperatures, yet they still suffer from insufficient Li compatibility and slow kinetic, especially at ultra‐low temperatures. Herein, we rationally design and synthesize a new amphiphilic solvent, 1,1,2,2‐tetrafluoro‐3‐methoxypropane, for use in battery electrolytes. The lithiophilic segment is readily to solvate Li+to induce self‐assembly of the electrolyte solution to form a peculiar core‐shell‐solvation structure. Such unique solvation structure not only largely improves the ionic conductivity to allow fast Li+transport and lower the desolvation energy to enable facile desolvation, but also leads to the formation of a highly robust and conductive inorganic SEI. The resulting electrolyte demonstrates high Li efficiency and superior cycling stability from room temperature to −40 °C at high current densities. Meanwhile, anode‐free high‐voltage cell retains 87 % capacity after 100 cycles.

Effect of the Surface Modification of Silica Nanoparticles on the Viscosity and Mechanical Properties of Silica/Epoxy Nanocomposites

ABSTRACT Silica/epoxy hybrid resin has high viscosity owing to its particle size and aggregation in the epoxy matrix, which leads to poor usability and processability. To control the size of the silica nanoparticles, surface modification of the colloidal silica (12 nm) was conducted in two steps using a silane coupling agent. The silica nanoparticles were then dispersed in the epoxy resin using an amphiphilic solvent with a high boiling point instead of mechanical dispersion. A nanosilica/epoxy hybrid resin with a low viscosity was obtained. The hybrid resin containing 3 wt% silica nanoparticles obtained a viscosity value that is 1.2% that of the neat epoxy resin. The tensile and flexural strengths of the silica/epoxy nanocomposite, as well as the impact strength of the silica/epoxy nanocomposite, were improved by plastic deformation cause by the introduction of silica nanoparticles. With silica nanoparticles loading of 10 wt%, the tensile strength of the silica/epoxy nanocomposite increased by 24%, and the impact strength increased by 112%. For higher amounts of loaded silica nanoparticles, the tensile strength of the silica/epoxy nanocomposite continuously increased, while the impact strength decreased.

Determination of ionization constants for sequinidazole in aqueous solutions and mixtures of water with isopropanol, acetonitrile and ethanol

Seknidazole is a drug from the 5-nitroimidazole group with a number of side-effects. This drug is virtually unexplored from the point of view of chemico-toxicological analysis (CTA). Therefore, the development of a set of methods for the detection and quantification of secnidazole in biological fluids for use in CTA is an urgent task. Aim. To study the acid-base equilibrium of secnidazole in aqueous solutions and mixtures of water with amphiphilic solvents and determine the corresponding ionization constants. Materials and methods. Spectrophotometric measurements were performed using a SPEKOL®1500 single-beam spectrophotometer. An EV-74 ionomer was used to control the pH of the solutions. Seknidazole solutions in the concentrationof 1000 μg/ml were used in the experiment. Results and discussion. Absorption spectra of secnidazole in water and mixtures of water and amphiphilic solvents in the pH range studied showed four isobestic points characterizing two protolytic equilibria (equilibrium 1 – 240 and 295 nm, equilibrium 2 – 261 and 297 nm). The position of the isobestic points of equilibrium 2 fluctuated in the range ± 3 nm; it was due to the presence of tautomeric transformations for the molecular form of secnidazole. Conclusions. The acid-base equilibria of secnidazole in aqueous solutions and mixtures of water with amphiphilic solvents have been studied. It has been shown that in a strongly alkaline medium there is an anionic form of secnidazole R–, with further decrease in the pH value the molecular form HR appears, in a strongly acidic medium the final product – a protonated form H2R+ – is formed. The ionization constant 1 has been determined for aqueous solutions of secnidazole, mixtures of water with isopropanol, acetonitrile and ethanol. It is impossible to determine the equilibrium constant 2 by the method specified.

Amphiphilic Deep Eutectic Solvent Based on Lidocaine and Lauric Acid: Formation of Microemulsion and Gel.

Deep eutectic solvent (DES), as a new type of promising green solvent, showed great advantages of easy preparation and no need for purification after synthesis and displayed great potential applications in various fields. Herein, we have constructed a new type of therapeutic DES based on lidocaine and lauric acid. The DES displayed good surface activity in constructing a nonaqueous microemulsion with 1,2-propanediol (PG) and isopropyl myristate (IPM) being the polar phase and nonpolar phase, respectively. The obtained nonaqueous microemulsion displayed a structural transition from W/O type to O/W type via a bicontinuous structure with an increase of the PG content. The size, morphology, and microstructure of the microemulsion were explored using dynamic light scattering (DLS), transmission electron microscopy (TEM), and UV-vis absorption spectra measurements. Furthermore, this novel DES can act as a gelator to form a gel in a certain water content range. The rheological measurements suggested the presence of a strong colloidal force. Therefore, the results presented herein were expected to provide a new perspective in the applications of deep eutectic solvent as a surfactant.

Anomalous interfacial dynamics of single proton charges in binary aqueous solutions.

Our understanding of the dynamics of charge transfer between solid surfaces and liquid electrolytes has been hampered by the difficulties in obtaining interface, charge, and solvent-specific information at both high spatial and temporal resolution. Here, we measure at the single charge scale the dynamics of protons at the interface between an hBN crystal and binary mixtures of water and organic amphiphilic solvents (alcohols and acetone), evidencing a marked influence of solvation on interfacial dynamics. Applying single-molecule localization microscopy to emissive crystal defects, we observe correlated activation between adjacent ionizable surface defects, mediated by the transport of single excess protons along the solid/liquid interface. Solvent content has a nontrivial effect on interfacial dynamics, leading at intermediate water fraction to an increased surface diffusivity, as well as an increased affinity of the proton charges to the solid surface. Our measurements evidence the notable role of solvation on interfacial proton charge transport.

The key to surfactant-free microemulsion demulsification: CO2 promotes the transfer of amphiphilic solvent to aqueous phase

In recent years, research on surfactant-free microemulsion (SFME) has given us new insight into the field of microemulsion. Here, we report a SFME with CO2 responsiveness prepared by mixing 1-dodecanol (oil phase), aqueous phase and N,N-dimethylethanolamine (DMEA, amphiphilic solvent) at appropriate proportion. The proportion of the three components used to prepare SFME was obtained by analyzing the ternary phase diagram of DMEA, 1-dodecanol and water. Meanwhile, the microstructure transition characteristics of SFME from oil-in-water (O/W) to bicontinuous phase (B.C.) to water-in-oil (W/O) was characterized by electrical conductivity and UV–Vis spectroscopy. In addition, the CO2 response behavior of W/O microemulsion has been studied deeply. We found that a significant demulsification phenomenon when CO2 was introduced into this SFME system. By measuring the concentration of DMEA in 1-dodecanol after demulsification, the demulsification mechanism of SFME can be confirmed: The introduction of CO2 causes the protonation of DMEA, and this process makes the amphiphilic solvent more soluble in the aqueous phase, which results in destabilization of this ternary system. Eventually, with the continuous introduction of CO2, the separation of the oil and water phases of SFME occurs.

In situ amphiphilic modification of thin film composite membrane for application in aqueous and organic solvents

Conventional support (uncrosslinked) based polyamide (PA) thin film composite (TFC) membranes are indispensable for desalination and purification of water. In addition to water purification, an emerging application of TFC membrane is the nanofiltration of organic solvents if the support layer is solvent resistant. However, solvent resistant PA TFC membranes show good permeate flux of polar solvents but low flux of non-polar solvents. We report that amphiphilic PA barrier layer is required to obtain good permeate flux of polar and nonpolar solvents. Herein, a facile approach for the in situ amphiphilic modification of PA layer of TFC membrane for application in aqueous and organic (polar and non-polar) medium is reported. Amphiphilic PA layers have been fabricated on conventional polysulfone (PSf) and solvent resistant polyimide (PI) supports. Interfacial polymerization (IP) between mixture of m-phenylenediamine (MPD) and MPD-capped polyethylene glycol (MPD-PEG-MPD) and mixture of trimesoyl chloride (TMC) and TMC-capped polydimethylsiloxane (TMC-PDMS-TMC) produces amphiphilic TFC membranes. Hydrophobic TFC membranes have been prepared by the IP between MPD and mixture of TMC and TMC-PDMS-TMC. The TFC membranes exhibit tunable water wetting behavior (water contact angle = 61-110o) depending on the composition of the organic phase. Amphiphilic TFC membranes show surface rearrangement/reconstruction behavior in contact with water and non-polar solvent. The amphiphilic membranes show good antifouling property with reduction of flux to about 14% and recovery in the flux to about 97% during desalination of water containing bovine serum albumin. The hydrophobic and amphiphilic TFC membranes (solvent resistant) showed significant improvement in the permeate flux of toluene and hexane. Particularly, amphiphilic solvent resistant membranes are suitable for application in water and nanofiltration of polar and non-polar solvents.

Supramolecular Depolymerization in the Mixture of Two Poor Solvents: Mechanistic Insights and Modulation of Supramolecular Polymerization of Ionic π‐Systems

AbstractSolvents are fundamentally essential for the synthesis and processing of soft materials. Supramolecular polymers (SPs), an emerging class of soft materials, are usually stable in single and mixtures of poor solvents. In contrast to these preconceived notions, here we report the depolymerization of SPs in the mixture of two poor solvents. This surprising behavior was observed for well‐known cationic perylene diimides (cPDIs) in the mixtures of water and amphiphilic organic solvents such as isopropanol (IPA). cPDIs form stable SPs in water and IPA but readily depolymerize into monomers in 50–70 vol% IPA containing water. This is due to the selective solvation of the π‐surface of cPDIs by alkyl chains of IPA and ionic side chains by water, as evidenced by molecular dynamic simulations. Moreover, by systematically changing the ratio between water and amphiphilic organic solvent, we could achieve an unprecedented supramolecular polymerization both by increasing and decreasing the solvent polarity.

Supramolecular Depolymerization in the Mixture of Two Poor Solvents: Mechanistic Insights and Modulation of Supramolecular Polymerization of Ionic π‐Systems

Solvents are fundamentally essential for the synthesis and processing of soft materials. Supramolecular polymers (SPs), an emerging class of soft materials, are usually stable in single and mixtures of poor solvents. In contrast to these preconceived notions, here we report the depolymerization of SPs in the mixture of two poor solvents. This surprising behavior was observed for well-known cationic perylene diimides (cPDIs) in the mixtures of water and amphiphilic organic solvents such as isopropanol (IPA). cPDIs form stable SPs in water and IPA but readily depolymerize into monomers in 50-70 vol% IPA containing water. This is due to the selective solvation of the π-surface of cPDIs by alkyl chains of IPA and ionic side chains by water, as evidenced by molecular dynamic simulations. Moreover, by systematically changing the ratio between water and amphiphilic organic solvent, we could achieve an unprecedented supramolecular polymerization both by increasing and decreasing the solvent polarity.

Human skin permeation rates ex vivo following exposures to mixtures of glycol ethers

Skin exposure to cleaning products in the general and occupational population are a public health concern. Among the most frequently identified amphiphilic organic solvents in cleaning products are propylene glycol monomethyl ether (PGME) and propylene glycol n-butyl ether (PGBE). Internal dose from skin exposure may be efficiently evaluated using in vitro flow-through diffusion cells with excised human skin. Our aim in this study was two-fold; 1) characterize the permeation rates (J), time lag (Tlag), and permeation coefficients (Kp) of PGME and PGBE in human ex-vivo skin permeation assays, and 2) determine a possible mixture effect on skin permeation characteristics when applied together. Our results showed a short Tlag for PGME and was reduced further depending on the amount of PGBE in the mixture (Tlag was reduced from 2 h to 1–1.7 h) for fresh skin. PGBE Tlag slightly increased when mixed with 50 % or more PGME. Permeation rate decreased to half for both PGME and PGBE in mixture at any concentration. This substantial permeation was greater with previously frozen skin. This mixture effect could favor permeation of other compounds through human skin.

Ultrafast Formation of the Charge Transfer State of Prodan Reveals Unique Aspects of the Chromophore Environment.

Lipophilic dyes such as laurdan and prodan are widely used in membrane biology due to a strong bathochromic shift in emission that reports the structural parameters of the membrane such as area per molecule. Disentangling of the factors which control the spectral shift is complicated by the stabilization of a charge-transfer-like excitation of the dye in polar environments. Predicting the emission therefore requires modeling both the relaxation of the environment and the corresponding evolution of the excited state. Here, an approach is presented in which (i) the local environment is sampled by a classical molecular dynamics (MD) simulation of the dye and solvent, (ii) the electronically excited state of prodan upon light absorption is predicted by numerical quantum mechanics (QM), (iii) the iterative relaxation of the environment around the excited dye by MD coupled with the evolution of the excited state is performed, and (iv) the emission properties are predicted by QM. The QM steps are computed using the many-body Green's function in the GW approximation and the Bethe-Salpeter equation with the environment modeled as fixed point charges, sampled in the MD simulation steps. The comparison to ultrafast time-resolved transient absorption measurements demonstrates that the iterative molecular mechanics (MM)/QM approach agrees quantitatively with both the polarity-dependent shift in emission and the time scale over which the charge transfer state is stabilized. Together the simulations and experimental measurements suggest that the evolution into the charge transfer state is slower in amphiphilic solvents.

Continuous growth phenomenon for direct synthesis of monodisperse water-soluble iron oxide nanoparticles with extraordinarily high relaxivity.

The direct synthesis of highly water-soluble nanoparticles has attracted intensive interest, but systematic size control has not been reported. Here, we developed a general method for synthesizing monodisperse water-soluble iron oxide nanoparticles with nanometer-scale size increments from 4 nm to 13 nm in a single reaction. Precise size control was achieved by continuous growth in an amphiphilic solvent, diethylene glycol (DEG), where the growth step was separated from the nucleation step by sequential addition of a reactant. There was only one reactant in the synthesis and no need for additional capping agents and reducing agents. This study reveals the "living growth" character of iron oxide nanoparticles synthesised in an amphiphilic solvent. The synthetic method shows high reproducibility. The as-prepared iron oxide nanoparticles are extremely water soluble without any surface modification. Surprisingly, the synthesized 9 nm iron oxide nanoparticles exhibit extremely high transversal and longitudinal relaxivities of 425 mM-1 s-1 and 32 mM-1 s-1 respectively, which is among the highest transversal relaxivity in the literature for sub-10 nm spherical nanoparticles. This study will not only shed light on the continuous growth phenomenon of iron oxide nanoparticles in an amphiphilic solvent, but could also stimulate the synthesis and application of iron oxide nanoparticles. The continuous growth method could be further extended to other materials for the controlled synthesis of water-soluble nanoparticles.

Anisotropic Nano-/Microparticles from Diversified Copolymers by Solvent-Mediated Self-Assembly.

Effective synthesis of anisotropic nano-/microparticles (APs) by the copolymers is of great significance in nanomaterials and nanotechnology. However, achieving regulation of the morphology, composition, property, and particle size of anisotropic nano-/microparticles (APs) with diversified copolymers is difficult due to complex mechanism and formation conditions. In this work, a versatile one-pot solvent-mediated self-assembly (SmSa) strategy had been proposed for the facile one-pot synthesis of shape-tunable anisotropic nano-/microparticles (StAPs). In addition, the formation mechanism of StAPs was determined through numerous characterization methods related to morphology and element distribution. The results revealed that the anisotropic architectures of StAPs were closely related to the nature of poly(methylacrylic acid-methyl methacrylate-butyl acrylate) (L1) and poly(butyl acrylate-styrene) (L2) polymer chains imparted by polymer blocks of different domains. Therefore, the ordered assembly of the rigid and hydrophobic L2 polymer chains in micelles consisting of the flexible and amphiphilic L1 and solvent could be successfully carried out under the mediation of increasing solvent polarity and the strong adsorption of poly(vinylpyrrolidone) for L2. Furthermore, the developed versatile SmSa strategy and the obtained StAPs play an essential role in the development of nanoscience and nanotechnology. Particularly given its adjustable emulsifying properties at different pH values, as well as numerous sites for further modification by fluorescent or other components, it can be employed to synthesize a wide range of functional materials.

Surface properties of the ethanol/water mixture: Thickness and composition

Ethanol is a common amphiphilic solvent often used in conjunction with water. However, despite its widespread use, key questions regarding the thickness and composition of molecules at the ethanol/water/air surface remain unclear. Recent thermodynamic analyses, Bagheri and co-authors (2016) and Santos and Reis (2018), indicated that the interfacial thickness is not constant. However, the interfacial thickness from these two analyses follows opposite trends. This study aims to provide a detailed description of the thickness and composition of the interfacial layer by combining neutron reflectivity (NR) experiments with rigorous molecular simulation. The interfacial composition was determined from molecular simulations and, in conjunction with the Gibbs excess concentration, used to calculate the interfacial thickness. It was found that the thickness decreased exponentially and reached a plateau of ~ 8.2 Å. The results confirm the trends obtained thermodynamically from surface tension. The study also provides a new theoretical framework to describe the interfacial layer of water/alcohol mixtures.