Nature Of Surfactant Research Articles

Role of ionic nature of surfactants on zinc stannate nanostructure and their application towards supercapacitors

This work demonstrates the role of cationic, anionic, and non-ionic surfactants [ethylene diamine (EDA), sodium lauryl sulfate (SLS), and triton X100 (TX100)] in synthesizing the phase pure zinc stannate (ZTO) nanostructures via hydrothermal technique. The X-ray diffraction (XRD) pattern reveals that EDA is a suitable surfactant for fabricating high crystalline ZTO nanostructures. The nature of surfactants alters the size and shape of the ZTO nanostructures, as evidenced by the FESEM micrographs. Specifically, hemi-pyramid embedded with fine spherical particles (EDA-assisted) and sphere-like particles (non and other surfactants) morphological features are observed. Their energy storage performance is evaluated through a three-electrode system. EDA-assisted ZTO delivered the specific capacitance value of 31 F/g at 1 A/g current density, slightly higher than that of the non-surfactant ZTO (27 F/g @ 1 A/g) electrode. Furthermore, the role of calcination is investigated, and it was found that the specific capacitance value is increased to 77 F/g (from 31 F/g) for the EDA-ZTO sample calcined at 600 °C for 3 h in an ambient atmosphere.Graphical abstract

Exploration of micellization and phase separation nature of surfactants in metformin hydrochloride + additives media: An experimental and DFT study

The study explores the aggregation and phase separation of a newly synthesized cationic surfactant − octadecyltriethylammonium bromide (OTEAB) and triton X-100 (TX-100) respectively with/without metformin hydrochloride (MMH) drug in absence/presence of NaCl. The conductivity measurements were performed to investigate the aggregation of cationic OTEAB at temperatures between 298.15 and 323.15 K with a 5 K gap. The micelle development of OTEAB in pure state and with MMH drug has been assessed by determining the critical micelle concentration (CMC). The reduction of CMC of OTEAB has been detected owing to the introduction of the MMH drug. The CMC was further decreased in attendance of NaCl. The CMC values also demonstrate the dependency on the change of temperature in all situations investigated. The decrease of CP values of triton X-100 and MMH mixture in aqueous NaCl was attained with the augmentation of the concentration of NaCl. The negative and positive values of free energy of micellization (ΔGm0) and clouding (ΔGc0) indicate the spontaneous and nonspontaneous nature of the respective processes. The enthalpy (ΔHm0) and entropy(ΔSm0) changes of the micellization were negative (exothermic) and positive, respectively. The enthalpy (ΔHc0) and entropy(ΔSc0) changes of the clouding were negative (exothermic) and positive, respectively, at lesser and higher concentrations of NaCl. The values of ΔHm0/ΔHc0 and ΔSm0/ΔSc0 designated that both hydrophobic and electrostatic interaction are present as important forces among the components under investigation. The thermodynamics of transfer and the enthalpy-entropy compensation parameters for the two processes were also computed and explained appropriately. Herein, we have also performed the computational analysis to find out the optimized structures, HOMO-LUMO orbitals, and the band gaps of OTEAB, MMH, and OTEAB+MMH mixture.

Lyotropic Aqueous 2-Picolinium Ionic Liquid Crystals and Their Shear-Induced Foams.

1-Dodecyl-2-methylpyridinium bromide ([C12-2-Pic][Br]) and 1-hexadecyl-2-methylpyridinium bromide ([C16-2-Pic][Br]) are two ionic liquid crystals presenting thermotropic smectic phases above 80 °C. Aiming to take advantage of the liquid crystalline properties at lower temperatures, lyotropic aqueous systems were prepared from these two organic salts. Both systems were characterized by polarized optical microscopy (POM), X-ray powder diffraction (XRD), and fast field cycling nuclear magnetic resonance (FFC-NMR) relaxometry to assess their texture, phase structure, and molecular dynamics, respectively. The mesomorphic behavior was induced at room temperature. Moreover, the lyotropic [C12-2-Pic][Br]aq revealed a smectic phase with higher separation between layers, different from the lamellar phases found in the thermotropic system (S1 and SA), which is thermally stable up to 50 °C. Furthermore, the surfactant nature of the ionic liquids diluted solutions investigated in this work allowed the formation of foams. It was found that the precursor solutions of the lyotropic dilutions with the longest alkyl chain ([C16-2-Pic][Br]aq) originated liquid foams with more stable structures than those of [C12-2-Pic][Br]aq.

Reactive species and mechanisms of perfluorooctanoic acid (PFOA) degradation in water by cold plasma: The role of HV waveform, reactor design, water matrix and plasma gas

The scope of this study was to optimize dielectric barrier discharge (DBD) plasma for the degradation of perfluorooctanoic acid (PFOA) in water by comparing several critical aspects such as pulsed-plasma waveform (nanosecond and microsecond high voltage (HV) pulses), reactor configuration (gas–liquid treatment and underwater plasma bubbles), water matrix and plasma gas. The physicochemical properties and species concentration of plasma-treated water, under the aforementioned conditions, were also determined and correlated with PFOA degradation. PFOA was more efficiently degraded by air–liquid DBD compared to DBD-based underwater air-plasma bubbles consistent with the surfactant nature of PFOA and the more intense plasma-liquid interaction and species formation prevailing during gas–liquid treatment compared to plasma bubbles treatment. After 30 min of gas–liquid DBD treatment, the degradation of PFOA in ultrapure water was >99.9, 98.8, 95.1 and 63% under air-, N2-, Ar- and O2-plasma respectively, whereas its degradation was almost equally effective in the whole range of its initial concentration (10 to 0.1 mg/L). Air was almost equally effective at degrading PFOA in ultrapure and tap water, while argon was much more effective at degrading PFOA in tap water (>99.9% after 20 min) possibly due to the prevailing alkaline conditions (pH ∼8.7) favoring its degradation. Faster PFOA degradation was achieved under HV micropulses compared to HV nanopulses. Nevertheless, in terms of energy requirements, HV nanopulses were superior to HV micropulses, with the lowest electrical energy per order achieved under nanopulsed-argon (∼23.6 kWh/m3). The results of this study could contribute important knowledge to the development of plasma-based treatment of PFOA-contaminated water.

Impact of the Amphoteric Nature of a Chelating Surfactant on its Interaction with an Anionic Surfactant: A Surface Tension and Neutron Reflectivity Study of Binary Mixed Solutions.

2-Dodecyldiethylenetriaminepentaacetic acid (C12-DTPA) is a chelating, amphoteric surfactant with a bulky headgroup containing eight pH-responsive groups. The hypothesis was that the amphoteric nature of the chelating surfactant would affect the interaction with another surfactant and, consequently, also the composition of mixed surface layers. Binary mixed monolayers of C12-DTPA and the anionic surfactant sodium dodecyl sulfate (SDS) were examined using neutron reflection and surface tension measurements. The experiments were conducted at pH 5, where the C12-DTPA monomers carried a net negative charge. Surface excess calculations at low total surfactant concentration revealed that the chelating surfactant dominated the surface composition. However, as the concentration was raised, the surface composition shifted toward an SDS-dominant state. This phenomenon was attributed to the increased ionic strength at increased concentrations, which altered the balance between competing entropic forces in the system. Interaction parameters for mixed monolayer formation were calculated, following a framework based on regular solution theory. In accordance with the hypothesis, the chelating surfactant's ability to modulate its charge and mitigate repulsive interactions in the surface layer resulted in favorable interactions between the anionic SDS and negatively charged C12-DTPA monomers. These interactions were found to be concentration-dependent, which was consistent with the observed shift in the surface layer composition.

Development of surfactant integrated polyaniline based electrode material towards supercapacitor application

Tailoring electrode material is always important for fabricating high-performance energy storage devices. Polyaniline (PANI) is one of the most-explored electrode materials due to its electroactivity, redox property, easy and cost-effective synthesis and reasonable capacitance. Herein, PANI has been integrated with surfactants (cetyltrimethylammonium bromide, dioctyl sodium sulfosuccinate, sodium lauryl sulphate, Tween-80) via chemical oxidative polymerization pathway and utilized as the electrode material for supercapacitor. Chemical nature, crystallinity and morphology of surfactant integrated PANI samples were evaluated by FTIR, UV–Visible, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques while electrochemical properties were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy studies. Among the different PANI samples, PANI integrated with cetyltrimethylammonium bromide (PMC) afforded 2.3 times higher capacitance (528 F/g) than PANI synthesized without surfactants (PM) (229 F/g). Due to the influence of CTAB, PMC displayed higher pore volume and lesser particle size as investigated by Brunauer-Emmett-Teller and dynamic light scattering analyses. Furthermore, PMC displayed two times higher electroactive surface area as compared to PM as investigated by cyclic voltammetry studies. It has been observed that the surfactant not only improved the processability of the polymer but also assisted in enhancing the capacitance of the electrode material significantly.

An industrially potent rhamnolipid-like biosurfactant produced from a novel oil-degrading bacterium, Bacillus velezensis S2.

Surfactants can reduce the interfacial surface tension between two immiscible liquids making them a desirable component for various industrial applications. However, the toxic nature of chemical surfactants brought immense attention towards biosurfactants. Being biodegradable, biosurfactants are eco-friendly and considered safer for different commercial uses. This study focused on the production of biosurfactant from an oil-degrading bacteria and its functional efficacy for prospective industrial applications. Here, a promising oil-tolerant strain, Bacillus velezensis S2 was isolated from oil contaminated sites which showed >50% degradation of convoluted crude oil within 28 days in comparison to a control. The isolate was then found to produce an excellent surface-active compound with an emulsification index of 67.30 ± 0.8% and could reduce the surface tension up to 36.86 ± 0.36 mN m-1. It also manifested a critical micelle concentration of 45 mg L-1 while reducing the surface tension from 72 to 30 mN m-1. When extracting biosurfactant from isolated bacteria, ethyl acetate extraction showed 1.5 times greater efficacy than chloroform : methanol extraction. The purified biosurfactant was characterized using TLC, 1H NMR, 13C NMR, FTIR, elemental analyses and spectrophotometric techniques leading to its identification as a rhamnolipid. The stability of produced biosurfactant at higher temperature (up to 180 °C) was determined by thermal analysis, endorsing its application in high temperature reservoir conditions. Additionally, the extracted biosurfactant showed excellent foaming efficacy with insignificant antibacterial and cytotoxic responses, which indicates their potential application in cleaning and cosmetics industries. Thus, the present study outlines a bi-functional novel isolate Bacillus velezensis S2 which could play a significant role in oil remediation from the environment as well as serve as a potential source of non-toxic and eco-friendly biosurfactants for various industrial applications.

Influence of Surfactant Structure on Polydisperse Formulations of Alkyl Ether Sulfates and Alkyl Amidopropyl Betaines.

Surfactants provide detergency, foaming, and texture in personal care formulations, yet the micellization of typical industrial primary and cosurfactants is not well understood, particularly in light of the polydisperse nature of commercial surfactants. Synergistic interactions are hypothesized to drive the formation of elongated wormlike self-assemblies in these mixed surfactant systems. Small-angle neutron scattering, rheology, and pendant drop tensiometry are used to examine surface adsorption, viscoelasticity, and self-assembly structure for wormlike micellar formulations comprising cocoamidopropyl betaine, and its two major components laurylamidopropyl betaine and oleylamidopropyl betaine, with sodium alkyl ethoxy sulfates. The tail length of sodium alkyl ethoxy sulfates was related to their ability to form wormlike micelles in electrolyte solutions, indicating that a tail length greater than 10 carbons is required to form wormlike micelles in NaCl solutions, with the decyl homologue unable to form elongated micelles and maintaining a low viscosity even at 20 wt % surfactant loading with 4 wt % NaCl present. For these systems, the incorporation of a disperse ethoxylate linker does not enable shorter chain surfactants to elongate into wormlike micelles for single-component systems; however, it could increase the interactions between surfactants in mixed surfactant systems. For synergy in surfactant mixing, the nonideal regular solution theory is used to study the sulfate/betaine mixtures. Tail mismatch appears to drive lower critical micelle concentrations, although tail matching improves synergy with larger relative reductions in critical micelle concentrations and greater micelle elongation, as seen by both tensiometric and scattering measurements.

Synthesis of biosurfactants by bacterial cells: Heavy-metals tolerance and siderophores

Environment unfriendly nature of chemical surfactants and pollution of the environment with heavy metals, especially from industries have become great challenges worldwide, hence the need for an urgent solution. This study aimed to search for novel strains exhibiting multiple industrial applications of heavy-metal tolerance, siderophore and biosurfactant capabilities. Soil samples were collected from industrial metal dumpsites and farmland soils. Isolation, enrichment and characterization of bacteria were carried out using biochemical and molecular techniques. Bacterial isolates were evaluated for heavy metals tolerance by agar-well diffusion and smear methods. Siderophore test was carried out using iron (III) chloride assay and isolates were employed in biosurfactant synthesis using solvent extraction method. Results showed that the prominent genus are Pseudomonas, Proteus, Staphylococcus and Micrococcus species. Resistance to heavy metals were observed to be higher at lower concentrations (100 mg/L) and reduced at higher concentrations (200–600 mg/L). Six isolates tolerated Ni at 600 mg/L and five bacterial isolates resisted Pb and Zn at 600 mg/L while other isolates displayed different inhibition zones. The evaluation of the isolates for siderophores synthesis revealed that only 5 bacterial isolates were positive. Among the positive biosurfactant producers, Burkholderia cepacia strain HB21 gave the highest biosurfactants yield (1.87 g/L and 0.96 g/L) while the least yield of 0.74 g/L and 0.38 g/L were produced by Achromobacter xylosoxidans strain 207–4B with and without agitation. These findings reveal that Burkholderia cepacia strain HB21 is a novel metal-tolerant strain with siderophore and biosurfactant producing potentials and may be useful for industrial applications

BAlGaN light‐emitting diode emitting at 350 nm

AbstractIn this work, the authors report the first demonstration of an ultraviolet light‐emitting diode (LED) with boron‐containing quantum wells (QWs). Secondary ion mass spectrometry measurements revealed a B concentration of 1% in the first QW with an increase in subsequent QWs and lingering decay into the p‐region, likely attributable to boron's surfactant nature. Electroluminescence emission from the BAlGaN LED was observed at 350 nm, with higher intensity compared to the AlGaN reference LED at low currents. A higher operating voltage compared to the reference LED was also observed which may be attributable to a nanomasking behaviour of boron in (Al)GaN alloys.

Understanding the temperature-dependent workability of cement paste with polycarboxylate superplasticizer

This paper aims to clarify the role of polycarboxylate superplasticizer (PCE) on the workability of cement paste under different temperatures ranging from 5 to 35 °C. The temperature-induced change in the aggregate morphology of PCE has been studied to reveal its dispersion efficiency, given its surfactant nature. The results indicate that the workability of cement paste with PCE gradually increases with a rise in temperature, and a similar trend is observed in quartz powder paste, where the effect of hydration can be disregarded. The improvement in dispersing efficiency of PCE is attributed to it being adsorbed as aggregates in both cement and quartz powder systems. Usually, the concentration of PCE in the cement interstitial solution exceeds the critical micellar concentration (CMC), which results in PCE aggregating in size but exhibiting numerous reconstituted branch chains. These findings suggest that cement hydration was not a dominant factor affecting the workability of cement paste at an early stage (within 10 min) with temperature rise, which makes PCE aggregate and enhances its dispersion efficiency in cement-based materials.

Synthesis of WO3 nanopowder using a green surfactant for efficient gas sensing applications

WO3 has attracted great attention for chemical gas sensing applications. However, the synthesis of WO3 is mainly performed by using hazardous organic solvents and corrosive acidic solutions, which can result in environmental and health issues. The development of safe synthesis procedures using green compounds and solvents is in great demand to overcome the aforementioned drawbacks. Therefore, the effect of different eco-friendly chemical compounds on the growth of WO3 materials has yet to be thoroughly studied. Meanwhile, the fabrication of material at the nanoscale with specific crystalline properties may improve its sensitivity to the target gas. In this work, we report an efficient method for the synthesis of WO3 nanopowder by using water and a green surfactant such as vitamin C. The growth mechanism of the structure is analyzed considering the nature of solutions and surfactants. The studies indicate that the surfactant has a crucial effect on the formation of nanoparticles. Furthermore, the experimental findings show that the fabricated monoclinic WO3 material is highly sensitive and selective to low concentrations of acetone. Moreover, the structure exhibits quite stable functionalities at different levels of environmental humidity. Hence, this work may have a considerable impact on the existing techniques for the preparation of WO3 nanomaterials providing new insights into their green synthesis procedures. In addition, it can significantly affect the development of high-performance gas sensors and other catalytic devices based on WO3 nanostructures.

Coarse-grain molecular dynamics simulation framework to unravel the interactions of surfactants on silica surfaces for oil recovery

A coarse-grained molecular dynamics (CG-MD) framework, based on the MARTINI 3.0 model, was developed to characterise the interactions between surfactants and oil-silica substrates to resemble chemical enhanced oil recovery (EOR) processes. Previous computational studies, at the atomistic scale, addressed interactions between surfactants and oil over diverse surfaces. Even though simulations provided significant information involved throughout different stages of oil extraction from surfaces, atomistic scale simulations fail when approaching the time and size scale required to address the surfactant phase behaviour that can also impact the oil detachment. Our coarse-grained model aims to overcome the lack of computer approaches that can tackle the surfactant self-assembly and the formation of ordered structures in the removal of oil from silica substrates. A new MARTINI 3.0 coarse-grain framework to model silica surfaces and aqueous solutions of CiEj and C16TAB surfactants is presented. Coarse-grained simulations entailing a silica surface, covered by dodecane or eicosane were brought in contact with aqueous solutions of C16TAB and four nonionic CiEj (C8E6, C8E12, C12E6, C16E12) surfactants to resemble EOR processes with a size/time scale several orders of magnitude larger than previous simulations. The impact of concentration and hydrophilic-lipophilic balance (HLB) of surfactants on the detachment of dodecane and eicosane from the silica surface was evaluated by visual inspection of the simulation snapshots and the evolution of the solvent accessible surface areas (SASA). In contrast with previous atomistic simulations, nonionic surfactants seem the best candidates for an optimal oil removal from silica-based surfaces whereas the presence of charged moieties hinders the process. Diluted nonionic CE aqueous solutions were shown to be the most effective solutions, unlike more concentrated ones. When compared with dodecane, eicosane was less prone to be removed from the silica surface due to the increased alkyl chain length. Our study demonstrates that not only the surfactant nature but also the phase behaviour, clearly impact the detachment of oil from silica surfaces. This is an important aspect to consider for a proper choice of surfactants in EOR processes, that is only attainable through a coarse-grained framework.

Ultrasound Emulsification in Microreactors: Effects of Channel Material, Surfactant Nature, and Ultrasound Parameters

Ultrasound Emulsification in Microreactors: Effects of Channel Material, Surfactant Nature, and Ultrasound Parameters

Investigation into Rheological Behavior of Warm-Mix Recycled Asphalt Binders with High Percentages of RAP Binder

The rheological properties of warm-mix recycled asphalt binders are critical to enhancing design quality and interpreting the performance mechanisms of the corresponding mixtures. This study investigated the rheological behavior of warm-mix recycled asphalt binders with high percentages of RAP binder. The effects of two warm-mix additives [wax-based Sasobit (S) and surfactant-based Evotherm-M1 (E)], a rejuvenating aging [ZGSB (Z)], four RAP binder contents (0%, 30%, 50% and 70%), and three aging states (unaged, short-term aged and long-term aged) were evaluated in detail using the dynamic shear rheometer (DSR), bending beam rheometer (BBR) and Brookfield rotational viscometer tests as well as conventional performance tests over the whole range of temperatures. The results showed that the rejuvenating agent Z effectively alleviated the aging effect of the RAP binder; however, it could hardly eliminate entirely this negative impact, especially at higher RAP binder contents. The addition of S remarkably lowered the apparent viscosity of the warm-mix recycled binders by up to 35.0%, whereas E had little influence on the binder viscosity due to its surfactant nature. Besides, S performed much better in improving rutting resistance (with the increase of up to 411.3% in |G*|/sinδ) than E, while E exhibited superior fatigue performance (with the reduction of up to 42.3% in |G*|·sinδ) to that of S. In terms of the thermal cracking resistance, E had very slight influence and S even yielded an adverse impact (with the increase of up to 70.2% in Sa and the decrease of up to 34.1% in m-value). Further, S broadened the ranges of pavement service temperatures by about 12 °C, whereas E almost did not change the PG grades of the binders. Finally, regarding the characteristics of viscoelastic master curves, S considerably improved the dynamic modulus and lowered the phase angle of the binders over a wide range of frequencies and temperatures but led to the failure of the time-temperature superposition principle due to its thermorheologically complex nature. Nevertheless, in this regard, the effect of E was found very mild.

Micellization pattern of cationic surfactants in presence of azo dye in methanol mixed media

Conductivity measurements at three different temperatures (298.15, 308.15, and 318.15 K) were performed to determine the micellization nature of cationic surfactants, i.e., dodecyl trimethylammonium bromide (DTAB) and cetylpyridinium chloride (CPC), in the absence and presence of the azo dye methyl red (MR) in four mixed solvent systems (0.1 to 0.4) volume fraction of methanol in water. We calculated the critical micelle concentration (CMC) of DTAB and CPC and the degree of ionization (α) for both in the absence and presence of MR using William’s method. The interaction of surfactants DTAB and CPC with MR has been identified separately through the dye-surfactant aggregation process, with reduced CMC values due to the molecular reorientation of methyl red in the systems. Micellization becomes more likely with MR due to the formation of a molecular complex in mixed systems. We calculated different thermodynamic properties both in the absence and presence of methyl red. Such parameters are the standard Gibbs free energy of micellization (ΔGmo), the standard enthalpy of micellization (ΔHmo), the standard entropy of micellization (ΔSmo), the standard free energy of transfer (ΔGtranso) and heat capacity of micellization (ΔmCp0). In accordance with ΔGmo values, the mixtures show the spontaneous nature of micellization of DTAB and CPC with MR as well.

Microbial Biosurfactant as an Alternate to Chemical Surfactants for Application in Cosmetics Industries in Personal and Skin Care Products: A Critical Review.

Cosmetics and personal care items are used worldwide and administered straight to the skin. The hazardous nature of the chemical surfactant utilized in the production of cosmetics has caused alarm on a global scale. Therefore, bacterial biosurfactants (BS) are becoming increasingly popular in industrial product production as a biocompatible, low-toxic alternative surfactant. Chemical surfactants can induce allergic responses and skin irritations; thus, they should be replaced with less harmful substances for skin health. The cosmetic industry seeks novel biological alternatives to replace chemical compounds and improve product qualities. Most of these chemicals have a biological origin and can be obtained from plant, bacterial, fungal, and algal sources. Various biological molecules have intriguing capabilities, such as biosurfactants, vitamins, antioxidants, pigments, enzymes, and peptides. These are safe, biodegradable, and environmentally friendly than chemical options. Plant-based biosurfactants, such as saponins, offer numerous advantages over synthetic surfactants, i.e., biodegradable, nontoxic, and environmentally friendly nature. Saponins are a promising source of natural biosurfactants for various industrial and academic applications. However, microbial glycolipids and lipopeptides have been used in biotechnology and cosmetics due to their multifunctional character, including detergency, emulsifying, foaming, and skin moisturizing capabilities. In addition, some of them have the potential to be used as antibacterial agents. In this review, we like to enlighten the application of microbial biosurfactants for replacing chemical surfactants in existing cosmetic and personal skincare pharmaceutical formulations due to their antibacterial, skin surface moisturizing, and low toxicity characteristics.

INFLUENCE OF THE PHASE TRANSFER CATALYST ON THE ACCUMULATION AND DECOMPOSITION OF ETHYLBENZENEHYDROPEROXIDE

The regularities of ethylbenzene oxidation and hydroperoxide decomposition in microheterogeneous systems formed by adding sodium dodecyl sulphate to hydrocarbon media have been studied. A pronounced influence of surfactant nature on the transformation mechanism has been revealed. Anionic micellar surfactants including a linear hydrocarbon fragment catalytically accelerate ROOH decomposition, whereas hydrocarbon soluble non-ionic surfactants and solid oxides practically do not influence the reaction rate. Detailed study of the degradation kinetics in the presence of anionic alkyl sulphates has shown that the accelerating effect of surfactants is connected with their colloidal properties, namely, with the formation of joint aggregates of inverse micelles type, which facilitate the destruction of the peroxide bond. For the first time, a synergistic inhibitory effect of sodium alkyl sulphate mixtures with phenolic antioxidants in the oxidation of various hydrocarbons has been found. During the oxidation of ethylbenzene with minor additives (<1%) of sodium dodecyl sulphate (DDS) a unique case of effective self-inhibition has been determined, the mechanism of which includes two steps. Hydroperoxide, the main source of free radicals, decomposes heterolytically in joint microaggregates with DDS. The decomposition occurs selectively with the formation of acetaldehyde and phenol. Phenol being an acceptor of free radicals inhibits the oxidation of ethyl benzene. The main oxidation product of RH in this system is phenol and acetaldehyde. It should be noted that phenols formation at decomposition of alkylaromatic ROOH is usually connected with strong acids. In the case of DDS decomposition of ROOH seems to be driven by the successful orientation of ROOH molecules in the microaggregates formed by anionic surfactants. But a number of experimental factors, namely the influence of the carbon chain length in sodium alkyl sulphates on the dodecane oxidation rate and inertness of the Na2SO4 dispersion in the hydroperoxide decomposition reactions, make it possible to suggest the catalytic reaction of ROOH. Suggest that the catalytic effect of DDS on hydroperoxide decomposition is connected with its colloidal properties and decomposition occurs in common microaggregates formed by DDS and ROOH. The effective activation energy of ROOH decomposition at concentration of 10 mm is Eef = 66.3 kJ/mol. The oxidation of ethyl benzene is completely inhibited at low additions of DDS (1 mM), and the decomposition rate in an atmosphere of N2 significantly increases. DDS increases the effective decomposition constant of ROOH. This surfactant can be considered as an effective catalyst of ROOH decomposition. For citation: Kashkay A.M. Influence of the phase transfer catalyst on the accumulation and decomposition of ethylbenzenehydroperoxide. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 2. P. 100-106. DOI: 10.6060/ivkkt.20236602.6684.

Cryogels loaded with nanostructured fluids studied by ultra-small-angle X-ray scattering

The combination of nanostructured fluids (NSFs), such as micellar solutions or microemulsions and highly-retentive hydrogels, such as PVA-based cryogels, represents nowadays a promising and innovative approach in the field of conservation of cultural heritage, as it enables the highest control available during cleaning interventions. However, at present, little is known about the confinement of NSFs into PVA-based cryogels. In the present work, small-angle X-ray scattering (SAXS) and ultra-small-angle X-ray scattering (USAXS), combined with fluorescence correlation spectroscopy (FCS), were used to address this issue. Two significantly different NSFs were selected for this purpose, based on anionic or nonionic surfactants, and they were confined into four different gels: two single PVA and two PVA/PVA “twin-chain polymer networks” (TC-PNs). The analysis of the experimental results shows that surfactant nature is crucial in determining the interaction of NSFs with the gels’ polymer network. Moreover it was demonstrated that loading NSFs on PVA-based cryogels does not significantly affect the short-range nanostructure of neither the NSFs nor the gels, preserving the cleaning performances of the combined system.

Distributions of α- and δ-TOCopherol in Intact Olive and Soybean Oil-in-Water Emulsions at Various Acidities: A Test of the Sensitivity of the Pseudophase Kinetic Model.

During the last years, the formalism of the pseudophase kinetic model (PKM) has been successfully applied to determine the distributions of antioxidants and their effective interfacial concentrations, and to assess the relative importance of emulsion and antioxidant properties (oil and surfactant nature, temperature, acidity, chemical structure, hydrophilic-liphophilic balance (HLB), etc.) on their efficiency in intact lipid-based emulsions. The PKM permits separating the contributions of the medium and of the concentration to the overall rate of the reaction. In this paper, we report the results of a specifically designed experiment to further test the suitability of the PKM to evaluate the distributions of antioxidants among the various regions of intact lipid-based emulsions and provide insights into their chemical reactivity in multiphasic systems. For this purpose, we employed the antioxidants α- and δ-TOCopherol (α- and δ-TOC, respectively) and determined, at different acidities well below their pKa, the interfacial rate constants kI for the reaction between 16-ArN2+ and α- and δ-TOC, and the antioxidant distributions in intact emulsions prepared with olive and soybean oils. Results show that the effective interfacial concentration of δ-TOC is higher than that of α-TOC in 1:9 (v/v) soybean and 1:9 olive oil emulsions. The effective interfacial concentrations of tocopherols are much higher (15-96-fold) than the stoichiometric concentrations, as the effective interfacial concentrations of both δ-TOC and α-TOC in soybean oil emulsions are higher (2-fold) than those in olive oil emulsions. Overall, the results demonstrate that the PKM grants an effective separation of the medium and concentration effects, demonstrating that the PKM constitutes a powerful non-destructive tool to determine antioxidant concentrations in intact emulsions and to assess the effects of various factors affecting them.