Lower Water Fraction Research Articles

A long-wavelength fluorescent probe based on carbazole with AIE characteristics for the detection of ONOO− and its application

Peroxynitrite (ONOO−) is an important reactive oxygen species, and excess ONOO− in the body can lead to a range of diseases. Addressing the need for sensitive detection ONOO−, in this work, a highly sensitivity and selectivity long-wavelength fluorescent probe (named CIS) was designed for tracking ONOO− in biological cells. Probe CIS featured carbazole as the fluorophore and the CC double bond with two electron withdrawing –CN groups as the recognition site. The probe CIS exhibited the typical aggregation-induced emission (AIE) and intramolecular charge transfer (ICT) characteristics with the bright red fluorescent emission in high water fraction (fw ≥ 50 %) and negligible emission in low water fraction. The fluorescence emission wavelength of probe CIS is 631 nm, with a large Stokes shift (151 nm), which can sensitively detect ONOO− in DMSO: H2O (7:3, v/v) environment. Notably, the probe CIS exhibited a wide pH detection range (pH = 3–10), a low detection limit of 36.66 nM, high selectivity and minimal interference. Furthermore, probe CIS demonstrated excellent biocompatibility and low cytotoxicity, and can be used for the detection of exogenous ONOO− in 4T1 cells (Mouse breast cancer cells). These research results indicate that probe CIS has potential application prospects in the biological aspects.

A visualizable strategy to real-time monitor chiral block copolypeptide assembly by AIE fluorescent probes

Aggregation-induced emission (AIE) luminogens show great potential in many applications. In this study, we have synthesized diblock copolymers poly (ethylene glycol) -b-poly (9-anthrylmethyl-L-lysine) (PEG-b-PLLys-An) and poly (ethylene glycol) -b-poly (9-anthrylmethyl-D-lysine) PEG-b-PDLys-An with opposite handedness by ring-opening polymerization and post-modification. Both diblock copolymers can self-assemble into spherical micelles or planar connected disc-like aggregates at different water fractions. In addition, the copolymers present a typical AIE process concomitant with the self-assembly process. To facilitate the study of chain exchange kinetics, we develope a novel visualizable strategy based on fluorescence variation. This strategy allows us to monitor the real-time chain exchange process by mixing equimolar solutions of PEG44-b-PDLys20-An and PEG44-b-PLLys20-An with varying water volume fractions. We indicate that chain exchange predominantly occurs at low water fractions through a single-molecule extraction and redistribution mechanism rather than micellar fission and fusion. In contrast, the micelles appear to be "kinetically frozen" at high water fractions, suggesting suppressed chain exchange under these conditions. Importantly, our approach offers a visually observable method for probing the dynamics of micellar chain exchange in real time.

A novel AIE peptide-based fluorescent probe for highly selective detection of mercury(II) ions and its application in food samples and cell imaging

A novel peptide-based fluorescent probe TPE-PGH was firstly developed based on aggregation-induced emission (AIE) effect. The fluorescence intensity of TPE-PGH was largely ignored in the low water fraction, whereas bright blue fluorescence was observed in the high water fraction. TPE-PGH achieved high selectivity and rapid detection of Hg2+, and has excellent sensitivity to detect Hg2+ with low LOD (58.1 nM). Interestingly, TPE-PGH provided a significant color changed from dark blue to bright cyan upon binding with Hg2+ ions under UV lamp (365 nm). In addition, TPE-PGH was able to simultaneously visualize Hg2+ in living cells with different fluorescence intensities based on excellent cells permeability and low toxicity. Further, TPE-PGH exhibited high precision (RSD < 4 %), and was successfully applied for detecting Hg2+ in real food samples, such as milk, soda drink, red wine, cucumber, tomato and carrot. Successful test strips responses also demonstrated that the potential of TPE-PGH for portable detection of Hg2+ in real samples. Especially, AIE based-test strips soaked in different Hg2+ concentrations was successfully utilized for semi-quantitative detection of Hg2+ using the RGB APP installed on a smartphone, which will provide a new approach for smart and portable detection of contaminated heavy metal ions in food samples.

Insight into the Molecular Structure, Interaction, and Dynamics of Aqueous Reline Deep Eutectic Solvent: A Nuclear Magnetic Resonance Investigation

Reline, which is composed of choline chloride (ChCl) and urea, is the first and most widely used deep eutectic solvent (DES) described by Abbot and co-workers. Due to the hygroscopic feature, traces of water are unavoidable, which significantly affect the physicochemical properties of reline. At present, the local structure of molecules and the impact from the presence of water are still the most significant questions in this field. Herein, reline and six aqueous dilutions with a controlled amount of water (from 3.2 to 50.0 wt %) were studied mainly by using a combination of nuclear magnetic resonance (NMR) techniques. According to 1D 35Cl NMR, 1D 15N NMR, and 2D 1H-15Cl heteronuclear Overhauser effect spectroscopy, we probed the interactions of urea···Cl- and Ch+···Cl- in pure reline, which gradually dissociated in the presence of water. Moreover, it was revealed that the dissociation rate altered when the water content reached 9.0 wt %, which is ascribed to the higher preference of hydration for Cl- ion compared to other species in the system. Furthermore, selected cross peaks in 1H-1H correlation spectroscopy spectra were analyzed. Accordingly, an enhanced correlation was observed for urea···Ch+ at a lower water fraction within 9.0 wt %. When the water content increased to 24.9 wt %, the water solvation of Ch+ and urea was also observed in COSY spectra. The interaction of H2O···Ch+ got continuously stronger when the water content increased from 24.9 to 50.0 wt %, while H2O···urea got enhanced when the water content reached 33.3 wt % and then diminished gradually from 33.3 to 50.0 wt %. 1H-1H nuclear Overhauser effect spectroscopy and 1H-1H rotating frame Overhauser effect spectroscopy experiments were also conducted for dynamics investigation. The τc value for the species in 9.0 wt % aqueous reline is very close to τccrit of 0.44 ns. For pure reline and the aqueous reline with a water fraction of less than 9.0 wt %, the τc value of the species is longer than 0.44 ns, while for the sample with water of 24.9 wt %, the τc value is much shorter than 0.44 ns. Based on our NMR study, we revealed that with the water amount increasing from 0 to 50.0 wt %, the species involved in the system behaved as the large molecules or molecules in viscous liquids transiting to the medium-sized molecules in nonviscous liquids and finally to small molecules in nonviscous liquids.

A fluorescent probe based on triphenylamine with AIE and ICT characteristics for hydrazine detection

A fluorescent probe MAM based on triphenylamine scaffold was synthesized. The electron donating group 4-methoxyphenyl and the electron acceptor dicyanoethylene were introduced on the triphenylamine scaffold to form a D-π-A fluorescent probe. The probe MAM exhibited the typical aggregation-induced emission (AIE) and intramolecular charge transfer (ICT) characteristics with the bright orange-red fluorescent emission in high water fraction (fw ≥ 50%) and negligible emission in low water fraction. The probe MAM could detect hydrazine (N2H4) in DMSO-tris-HCl (10 mM, pH7.4, v/v, 3:1) with high selectivity and sensitivity. The specific reaction between MAM and hydrazine and the formation of the hydrazone blocked the ICT process, and the system emitted the cyan fluorescence which could be easily observed by naked eyes. The limit of detection (LOD) was 0.196 μM (6.25 ppb), which is lower than the US Environmental Protection Agency standard (10 ppb). The test strips prepared by the probe MAM could realize the convenient and rapid detection of N2H4 solution and vapor. The application of MAM in actual water samples and cells was investigated, and the results showed that MAM could sense N2H4 in environmental and biological aspects with potential application prospects.

Predicting the Water Content of Interstellar Objects from Galactic Star Formation Histories

Abstract Planetesimals inevitably bear the signatures of their natal environment, preserving in their composition a record of the metallicity of their system’s original gas and dust, albeit one altered by the formation processes. When planetesimals are dispersed from their system of origin, this record is carried with them. As each star is likely to contribute at least 1012 interstellar objects (ISOs), the Galaxy’s drifting population of ISOs provides an overview of the properties of its stellar population through time. Using the EAGLE cosmological simulations and models of protoplanetary formation, our modeling predicts an ISO population with a bimodal distribution in their water mass fraction: objects formed in low-metallicity, typically older, systems have a higher water fraction than their counterparts formed in high-metallicity protoplanetary disks, and these water-rich objects comprise the majority of the population. Both detected ISOs seem to belong to the lower water fraction population; these results suggest they come from recently formed systems. We show that the population of ISOs in galaxies with different star formation histories will have different proportions of objects with high and low water fractions. This work suggests that it is possible that the upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time will detect a large enough population of ISOs to place useful constraints on models of protoplanetary disks, as well as galactic structure and evolution.

Development and characterization of a novel naturally occurring pentacyclic triterpene self-stabilized pickering emulsion

Phytochemicals self-stabilized Pickering emulsion is expected to be a highly desirable oral self-delivery system. In this study, ursolic acid (UA), a representative pentacyclic triterpene, was reported for the first time that can be formed self-stabilized Pickering emulsion. That is, it is experimentally and theoretically proved that water-in-oil Pickering emulsion could be stabilized solely by UA. First, the morphology, wettability and interfacial properties of the UA particles were characterized. Then, the influence of variation with UA particle concentration (c) and water fraction (ϕ) on the droplet size and coalescence (and sedimentation) stability of UA stabilized emulsions were also studied. It was found that the formed emulsions performed excellent sediment stability except that under conditions where the UA particle concentration is low (c=1 wt%) or at low water fraction(ϕ=0.1). The viscoelastic properties of the emulsions could be improved with the increasing c or ϕ. Finally, The molecular dynamics simulation further verified that the UA particles are located at the oil-water interface and incompletely wrapped the water droplets to form a stable W/O Pickering emulsion. This work enriches the family of sustainable W/O Pickering stabilizers and provides a new strategy for the construction of a Carrier-Free Delivery System for pentacyclic triterpenes.

Research on the viscosity of stabilized emulsions in different pipe diameters using pressure drop and phase inversion

This paper reports experimental research on the flow behavior of oil-water surfactant stabilized emulsions in different pipe diameters along with theoretical and computational fluid dynamics (CFD) modeling of the relative viscosity and inversion properties. The pipe flow of emulsions was studied in turbulent and laminar conditions in four pipe diameters (16, 32, 60, and 90 mm) at different mixture velocities and increasing water fractions. Salt water (3.5% NaCl w/v, pH = 7.3) and a mineral oil premixed with a lipophilic surfactant (Exxsol D80 + 0.25% v/v of Span 80) were used as the test fluids. The formation of water-in-oil emulsions was observed from low water fractions up to the inversion point. After inversion, unstable water-in-oil in water multiple emulsions were observed under different flow regimes. These regimes depend on the mixture velocity and the local water fraction of the water-in-oil emulsion. The eddy turbulent viscosity calculated using an elliptic-blending k-ε model and the relative viscosity in combination act to explain the enhanced pressure drop observed in the experiments. The inversion process occurred at a constant water fraction (90%) and was triggered by an increase of mixture velocity. No drag reduction effect was detected for the water-in-oil emulsions obtained before inversion.

Effects of substituents on the optical properties of AIEE-active 9, 10-dithiopheneanthrylene derivatives and their applications in cell imaging

A series of asymmetric 9, 10-dithiopheneanthrylene derivatives (DTAs) with various substituent groups and large Stokes shifts (>80 nm) have been synthesized and characterized. All of them displayed aggregation-induced emission enhancement (AIEE) behaviors expect for DTA-M, which fluorescence was gradually enhanced in low water fraction (50%), but dramatically quenched with the increase of water fraction to 90% due to the twisted intramolecular charge transfer (TICT) effect. The size of particles in aggregates were studied by using a scanning electron microscope, indicating the formation of morphological diversity nanoparticles due to the various substituents on 2-position of lateral thiophene ring. Furthermore, all of them exhibited reversible mechanofluorochromic and vapochromic luminescence behaviors, especially compound DTA-M, which showed high color contrast mechanofluorochromism between yellow and red color. In addition to the AIEE and mechanofluorochromic properties, HeLa cells fluorescence imaging experiments proved that these DTAs are capable to achieving bioimaging.

Onset of water accumulation in oil/water pipe flow – experiments and modelling with LedaFlow

In oil/water flows with very low water rates, the steady-state water fraction jumps discontinuously from a low value to a high value when the oil rate falls below the critical value. This jump is understood to be connected to the existence of multiple solutions, and generally takes place when the oil rate becomes too low to sustain a low water fraction. We refer to this critical oil flow rate as the onset of water accumulation. Water accumulation in oil transport lines is undesirable because it can lead to corrosion problems that can threaten the integrity of the installation, potentially leading to oil leaking undetected into the environment, jeopardizing nearby wildlife and ecosystems. It is therefore critical to maintain a flow rate that is high enough to prevent water from accumulating in oil lines, and the ability to predict the minimum allowable flow rate accurately is thus of great importance. To address this challenge, a new and unique set of experiments were conducted at the SINTEF Multiphase Laboratory. The experiments were specially designed to measure the critical conditions for water accumulation in oil/water flows and were performed with a pipe diameter of 8 inches (194 mm) and a pipe inclination of 2.5 degrees. The fluid system consisted of Exxsol D60 as the oil phase and regular tap water as the aqueous phase. In these experiments, the measured critical superficial water velocities were in the range 0.1-2.6 mm/s, while the critical superficial oil velocities were in the range 0.3-0.5 m/s. We found that the customary approach of modelling the oil/water interfacial shear stress as a smooth wall was inadequate for predicting these experiments, and that interfacial waves must be considered. The data analysis showed that the onset of interfacial waves is well predicted by Viscous Kelvin-Helmholtz theory, and that a model for the interfacial shear stress can be constructed with this theory as a starting point. A new model for oil/water interfacial shear stress was developed based on this data and the associated data analysis. The new model was able to match the experimental data well and a slightly modified version of it was ultimately implemented in the commercial multiphase flow simulator LedaFlow.

Synthesis and photophysical properties of bis-tetraphenylene-diones

Bis-tetraphenylethene-diones (Bis-TPE-diones) can serve as key precursors for the synthesis of blue light-emitting OLED materials. In this paper, four Bis-TPE-diones with different dicarbonyl chains as linkers were elaborately designed for photophysical properties investigation. These Bis-TPE-diones have been facilely synthesized by F-C acylation in one step for the first time. Expensive and harmful reagents as well as harsh reaction conditions were excluded, which make our new method more economical and convenient. The AIE properties, solavatochromism and mechanochromism of the Bis-TPE-diones have also been carefully studied. The Bis-TPE-diones exhibited notable AIE properties and their maximum fluorescence in THF can be turned on by low water fractions (fw, 10%–40%). The fw to turn on the maximum fluorescence are closely associated with the dicarbonyl chain linkers in the Bis-TPE-diones as the following sequence: conjugate chain (fumaryl, fw = 10%) < flexible long chain (succinyl, fw = 20% < glutaryl, fw = 30%) < short chain (1,2-dicarbonyl, fw = 40%). This result could be ascribed to different polarities and conformations of the Bis-TPE-diones. Therefrom, a new strategy to turn on the maximum fluorescence of AIE-gens was proposed: The fw to turn on the maximum fluorescence of AIE-gens could be tuned by adjusting the length and the conjugation of the linker. This strategy could be instructive for design of other AIE molecules. The Bis-TPE-diones also exhibited notable solvatochromism, observable mechanochromism as well as good thermal stability. With these outstanding properties, the Bis-TPE-diones could be further applied in optoelectronic devices and other functional materials.

Aggregation Induced Emission Enhancement (AIEE) of Naphthalene‐ Appended Organic Moiety: An Al3+ Ion Selective Turn‐On Fluorescent Probe

AbstractAn example of an aggregation‐induced emission enhancement (AIEE)‐active new naphthalene appended Schiff base (H2L) as an Al3+ ion selective fluorescent sensor has been successfully designed and synthesized. H2L showed turn‐on fluorescence at high concentration in DMF only, and at low concentration in DMF‐H2O mixtures having high water content (more than 20%). But at very low concentration of H2L and in DMF/H2O solutions with low water fraction (fw ≤ 20%), the fluorescence was turned ON in presence of Al3+ ions, which helps to detect Al3+ ions as low as 4.9×10−7 M with high selectivity in an DMF solution without any interference of other competitive metal ions. The fluorescence of H2L in different conditions and in solid state due to AIE effect has been established with the help of detailed spectroscopic studies, dynamic light scattering (DLS), scanning electron microscope (SEM), life time using time‐resolved photoluminescence and optical fluorescence microscope. The experimentally observed H‐type aggregation nature of the probe H2L has also been supported by the theoretical (DFT studies and TDDFT) studies. This probe (H2L) has also been employed for on‐site Al3+ ions detection in solid state.

Super-Earth masses sculpted by pebble isolation around stars of different masses

We developed a pebble-driven core accretion model to study the formation and evolution of planets around stars in the stellar mass range of 0.08 M⊙–1 M⊙. By Monte Carlo sampling of the initial conditions, the growth and migration of a large number of individual protoplanetary embryos were simulated in a population synthesis manner. We tested two hypotheses for the birth locations of embryos: at the water ice line or log-uniformly distributed over entire protoplanetary disks. Two types of disks with different turbulent viscous parametersαtof 10−3and 10−4are also investigated to shed light on the role of outward migration of protoplanets. The forming planets are compared with the observed exoplanets in terms of mass, semimajor axis, metallicity, and water content. We find that gas giant planets are likely to form when the characteristic disk sizes are larger, the disk accretion rates are higher, the disks are more metal rich, and/or their stellar hosts are more massive. Our model shows that first, the characteristic mass of super-Earth is set by the pebble isolation mass. Super-Earth masses increase linearly with the mass of its stellar host, which corresponds to one Earth mass around a late M-dwarf star and 20 Earth masses around a solar-mass star. Second, the low-mass planets, up to 20 M⊕, can form around stars with a wide range of metallicities, while massive gas giant planets are preferred to grow around metal rich stars. Third, super-Earth planets that are mainly composed of silicates, with relatively low water fractions, can form from protoplanetary embryos at the water ice line in weakly turbulent disks where outward migration is suppressed. However, if the embryos are formed over a wide range of radial distances, the super-Earths would end up having a distinctive, bimodal composition in water mass. Altogether, our model succeeds in quantitatively reproducing several important observed properties of exoplanets and correlations with their stellar hosts.

Pre-nucleation aggregation based on solvent microheterogeneity.

Investigation into pre-nucleation aggregates indicating hydrate formation of caffeine and theophylline in aqueous acetonitrile showed hydrate crystallisation at much lower water fraction than significant solute self-association. Molecular dynamics simulations indicate that the solvent separates on the molecular scale and that solute molecules preferentially localise on the phase interface.

Rapid myelin water imaging for the assessment of cervical spinal cord myelin damage.

BackgroundRapid myelin water imaging (MWI) using a combined gradient and spin echo (GRASE) sequence can produce myelin specific metrics for the human brain. Spinal cord MWI could be similarly useful, but technical challenges have hindered routine application. GRASE rapid MWI was recently successfully implemented for imaging of healthy cervical spinal cord and may complement other advanced imaging methods, such as diffusion tensor imaging (DTI) and quantitative T1 (qT1).ObjectiveTo demonstrate the feasibility of cervical cord GRASE rapid MWI in multiple sclerosis (MS), primary lateral sclerosis (PLS) and neuromyelitis optica spectrum disorder (NMO), with comparison to DTI and qT1 metrics.MethodsGRASE MWI, DTI and qT1 data were acquired in 2 PLS, 1 relapsing-remitting MS (RRMS), 1 primary-progressive MS (PPMS) and 2 NMO subjects, as well as 6 age (±3 yrs) and sex matched healthy controls (HC). Internal cord structure guided template registrations, used for region of interest (ROI) analysis. Z score maps were calculated for the difference between disease subject and mean HC metric values.ResultsPLS subjects had low myelin water fraction (MWF) in the lateral funiculi compared to HC. RRMS subject MWF was heterogeneous within the cord. The PPMS subject showed no trends in ROI results but had a region of low MWF Z score corresponding to a focal lesion. The NMO subject with a longitudinally extensive transverse myelitis lesion had low values for whole cord mean MWF of 12.8% compared to 24.3% (standard deviation 2.2%) for HC. The NMO subject without lesions also had low MWF compared to HC. DTI and qT1 metrics showed similar trends, corroborating the MWF results and providing complementary information.ConclusionGRASE is sufficiently sensitive to detect decreased myelin within MS spinal cord plaques, NMO lesions, and PLS diffuse spinal cord injury. Decreased MWF in PLS is consistent with demyelination secondary to motor neuron degeneration. GRASE MWI is a feasible method for rapid assessment of myelin content in the cervical spinal cord and provides complementary information to that of DTI and qT1 measures.

Stress-Driven Separation of Surfactant-Stabilized Emulsions and Gel Emulsions by Superhydrophobic/Superoleophilic Meshes

Oil-in-water (O/W) emulsions and gel emulsions which are stabilized by surfactants for more than 5 months have been successfully separated by a simple gravity-driven agitation-assisted device. The device contains a rotating magnetic stir bar and a flexible superhydrophobic/superoleophilic Cu mesh which has been folded into the desired three-dimensional shape. The emulsions were prepared by mixing various fractions of alkane and water (99–1%) stabilized by a water-soluble surfactant. For low water fractions which contained higher concentrations of the surfactant, solid-like gel emulsions were obtained. The stress-driven process was found to effectively separate stable emulsions with a separation efficiency ≥ 98% and gel emulsions with a separation efficiency as high as 96%. The mechanism for oil recovery from stable emulsions by our stress-driven device is based on the momentary breakage of the water barrier layer (superhydrophobicity) and the enhancement of the oil–mesh contact leading to oil permeation (...

Foam-Scattering Effects on Microwave Emission From Foam-Covered Ocean Surface

In this letter, we investigate volume-scattering effects on microwave emission from a foam-covered ocean surface by a comparative study of emissivities and polarization indexes of a numerical radiative transfer model and an incoherent emission model. The matrix doubling method is applied in the numerical model, which fully accounts for the multiple scattering in the foam layer and at the interfaces. The incoherent emission model considers incoherent interactions between air–foam and foam–seawater interfaces but ignores the volume scattering in the foam layer. Model analyses show that foam volume scattering affects both the magnitude and polarization index of emission from the foam-covered ocean surface. Foam volume scattering reduces the rate of increase in emissivity with increasing foam water fraction. Results also show that polarization index is more sensitive to volume scattering at a large observation angle and at a low foam water fraction. Comparison between model predictions and experimental measurements accentuate the need to account for foam-scattering effects in interpreting emission measurements from the foam-covered ocean surface.

Exploration of solvent responsive Cr3+-Schiff base conjugates formonitoring Cr3+ ions and organophosphates: Fabrication of spot-testingdevices

Herein, we report 2-((2-hydroxybenzylidene)hydrazono)(phenyl)methyl)-5-methoxyphenol (SB) synthesized by Schiff base condensation and characterized by spectroscopic techniques, elemental analysis and X-ray crystallography. In solution phase, it interacts with Cr3+ ions and exhibits a prominent fluorimetric switch due to the formation of SB·Cr3+ conjugate. The dual behavior of SB·Cr3+ conjugates i.e. self-aggregation in high water fraction (fw > 50%) and dissolution in low water fraction (fw < 50%) proves this conjugation excellent tool for monitoring Cr3+ ions. The SB·Cr3+ conjugate in methanol-water (70:30 v/v) allows quantification of Cr3+ ions with limit of detection 0.44 μM and its self-aggregation in high water fraction facilitates extraction of Cr3+ ions with 95% extraction efficiency. Although SB interacts with Zn2+ ions which causes inference in the determination of Cr3+ ions however the interferent can be easily masked with SCN− ions. Besides, the SB·Cr3+ conjugates are also able to quantify organophosphate neurotoxins; i.e. diethyl chlorophosphate (with LOD 4.1 nM) and diethyl cyanophosphonate (with LOD 3.3 nM) from aqueous solutions. Moreover, SB and SB·Cr3+ conjugates can be coated on solid surfaces to fabricate portable devices for the on-spot detection of targets from real samples. Hence, the conjugation of Schiff base and Cr3+ ions can be explored for the recognition, quantification and extraction of Cr3+ ions and detection of organophosphates.

Dielectric Relaxation of Hydration Water in Native Collagen Fibrils.

The dielectric relaxation of hydrated collagen powders was studied over a wide temperature and frequency range. We revealed two mechanisms of dielectric relaxation in hydration water that are driven by the migration of ionic and orientation defects. At high water fractions in powders (h > 0.2), the hydration shell around the collagen triple helixes presents a spatial H-bonded network consisting of structural water bridges and cleft water channels. These two water phases provide the long-range paths for proton hopping and orientation defect migration. At low water fractions (h < 0.2) and in the hydrated collagen samples after the dehydrothermal treatment, the hydration shell presents localized individual water compartments not connected to one another. In these cases, the relaxation mechanism due to proton hopping either disappears or becomes inhibited by the orientation defect migration.

CHEMICAL DEMULSIFICATION OF MODEL WATER-IN-OIL EMULSIONS WITH LOW WATER CONTENT BY MEANS OF IONIC LIQUIDS

The demulsification of model water-in-oil (w/o) emulsions containing 1% wt. water by [Omim][PF6] and Aliquat® 336 ionic liquids (IL) as demulsifiers was investigated in batch mode at different temperatures (30, 45 and 60 °C) and demulsifier concentrations (2.5×10‒3, 1.2×10‒2 and 2.9×10‒2 mol L‒1). The model oil is a mixture n-heptane/toluene (70/30% wt.) with 1% wt. of Span® 83 as a surfactant. Experimental results showed that the main differences in demulsification dynamics between systems containing IL and blank (i.e., in the absence of demulsifier) are detected at 30 °C and for short demulsification times (t≤4 h). In particular, the demulsification efficiency is 8, 21 and 74% for the blank sample, [Omim][PF6] and Aliquat® 336 tested under the more concentrated IL condition, respectively. The superior demulsification performances of Aliquat® 336 with respect to [Omim][PF6] were related to the greater molecular weight and more hydrophobic character of its cation, likely able to induce a faster desorption of the surfactant at the w/o interface and consequently promoting water droplet coalescence. Moreover, the kinetic demulsification data were successfully interpreted by an empirical pseudo-first order model. In general, the obtained outcomes encourage future research efforts in the use of ionic liquids for the removal of low water fractions from w/o emulsions.