Micellar Solutions Research Articles

Wormlike micellar solutions formed by an anionic surfactant and a cationic surfactant with two head groups.

Innovation in the molecular structure of surfactants is important for the preparation of soft materials with novel properties. In this study, we synthesized a cationic surfactant, N1,N1,N1,N1,N3,N3,N3-pentamethyl-N3-(3-stearamidopropyl)propane-1,3-diammonium bromide, hereafter referred to as C18-DQA. Unlike conventional cationic surfactants, C18-DQA contains two quaternary ammonium head groups and a long-saturated alkyl chain equal to a chain length of 21 carbon atoms. C18-DQA exhibits a low Krafft point of ∼0 °C and a water solubility >1000 mM at 25 °C. The critical micelle concentration (cmc) of C18-DQA was determined to be 0.59 mM using the Nile red method. C18-DQA was mixed with sodium laurate (SL) at different molar ratios to produce transparent solutions with excellent viscoelasticity over a wide concentration range. The 1 : 1.5 molar ratio C18-DQA/SL mixed solutions exhibited gel-like behavior for a total surfactant concentration of 2.88 wt% (75 mM). The solution with a total surfactant concentration of 300 mM (120 mM C18-DQA and 180 mM SL) achieved a maximum zero-shear viscosity (η0) of 4224 Pa s. Cryogenic transmission electron microscopy analysis revealed the formation of extremely long wormlike micelles, with a cross-sectional diameter of 5 nm and contour length >3 μm, in the mixed solutions. C18-DQA and SL molecules were drawn close by electrostatic attractions, leading to a suitable molecular geometry for the extensive growth of wormlike micelles. This work will act as an important reference for the future preparation of highly viscoelastic solutions by mixing cationic and anionic surfactants. The proposed system is also expected to have potential applications in cosmetic formulations, home care products, and oilfield fracturing fluids.

Lanthanide‐Containing Heteropolyoxomolybdate as Precursor to Porous Complex Oxides via Polymeric Micelle Assembly and Its Heterostructure with Carbon Dots for Anticounterfeiting Application

AbstractThe fabrication of porous complex oxides with intriguing opto‐functional properties remains a challenge that requires innovative synthetic strategies. In this work, a facile soft template method is developed based on stable micellar solutions formed with lanthanide‐containing heteropolyoxomolybdate and alkaline earth citrates as metal salt precursors and block copolymer as templates. The resulting structures exhibit an effective interfacial Förster resonance energy transfer (IFRET) between the porous CaMoO4:Eu3+ (CEMO) host and the embedded surface‐active carbon dots through the conjugated bonds between Ca2+/Mo6+ cations and the C═O functional groups. Such IFRET process extends of Eu3+ absorption band toward the UV and blue regions, enabling the proof‐of‐concept demonstration of multiresponsive anticounterfeiting codes. The study not only presents a new strategy to prepare porous lanthanide‐doped complex oxides but also provides a feasible way to achieve spectral regulation through interfacial interaction for multifunctional luminescent materials.

Сравнение двух типов подвижных фаз для определения витаминов группы В методом тонкослойной хроматографии

Thin-layer chromatography (TLC) has been used to study the influence of a number of factors (the nature of the stationary phase, the nature and concentration of the organic solvents and surfactants, the pH of the buffer solution) on the chromatographic characteristics of B vitamins: B 1 (thiamine), B6 (pyridoxine), B12 (cyanocobalamin). The stationary phases were plates with polar (Sorbfil on a polymer (highperformance plates, HTLC) and aluminum substrates), weakly polar (Polyamide-6), and nonpolar (RP-18 on an aluminum substrate) sorbents. As micellar mobile phases – micellar solutions of cetylpyridinium chloride in the concentration range 5–10-4 – 5–10-1 M, sodium dodecyl sulfate in the concentration range 2,5–10-4 – 5–10-1 М. It has been established that among aqueous-organic mobile phases (MF) the best results have been obtained for MF of the composition acetonitrile – water (15:385) on polar high-performance plates. More effective than acetonitrile – water is the PF of the composition acetonitrile – cetylpyridinium chloride (15:85) in the presence of a phosphate buffer solution with pH = 3. For the last PF, TLC determination of vitamins B1, B6, B12 in pharmaceutical preparations with a Sr value of interval 0.01–0.06 has been developed.

Rheology of novel photosensitive viscoelastic trimeric cationic surfactant/trans‐ortho‐methoxycinnamic acid micellar solutions

AbstractPhotosensitive micellar solutions of mixed surfactants and photosensitive additives have gained much interest. However, there are no reports on photosensitive micellar solutions containing trimeric cationic surfactant. In the study, novel photosensitive viscoelastic micellar solutions consisting of trimeric cationic surfactant (TEC) and trans‐ortho‐methoxycinnamic acid (trans‐OMCA) were investigated. This study utilized rheology, UV–vis spectroscopy, and cryo‐TEM to investigate the photo‐responsive behavior and mechanism of the TEC/trans‐OMCA micellar solutions. Rheological studies revealed that the concentration of TEC and trans‐OMCA, as well as temperature, significantly affected the viscoelastic properties of the micellar solutions. Furthermore, the Carreau and Maxwell models might be used to characterize the flow curves and viscoelasticity of the micellar solutions, respectively. Notably, TEC/trans‐OMCA micellar solutions exhibited excellent light‐induced thinning characteristic, with the optimal performance at a mass ratio of φ = 0.5. After UV irradiation, the zero‐shear viscosity of TEC/trans‐OMCA (0.6/0.3 wt%) micellar solution was reduced by 352 times, while the viscoelasticity and the area of hysteresis loops were significantly reduced. This drastic change in the rheological characteristics of the micellar solutions could be attributed to the photoisomerization of trans‐OMCA and the resulting changes in the internal microstructure of the solutions. Moreover, the viscosity of the micellar solutions diminished as the temperature increased, with the remaining viscosity of the TEC/trans‐OMCA (1.0/0.5 wt%) micellar solution at 36.4 mPa s at 95°C. This study expands on the potential utilization of oligomeric surfactants in the construction of photorheological viscoelastic fluids.

Experimental studies on self-propulsion of deformable 5CB liquid crystal droplets in micellar solution

ABSTRACT The 5CB liquid crystal droplets were found to self-propel when suspended in a micellar solution of surfactant. We report experimental studies on the motion of these droplets in a quasi-two-dimensional geometry. The droplets exhibit directed, self-avoiding, or random coiling trajectories depending on the size of the droplets compared to the height of the sample cell. The flattened droplets showed smoother trajectories and with self-crossing. Interestingly, the large flattened droplets were found to exhibit deformation of their apparent cross-section during their self-propulsive motion. These unique properties of self-propulsion of 5CB liquid crystal droplets in surfactant solution can provide a new opportunity to study active biomimetic systems.

Emergent properties of magnetic ions and nanoparticles in micellar solutions of surfactants: Use in fine technologies

Objectives. To establish expected emergent (unexpected) properties of magnetic materials when obtained in aqueous micellar solutions of surfactants (aqueous quantum materials), and their use in fine technologies.Methods. Chemical synthesis of magnetic nanoparticles in aqueous micellar solutions of surfactants of various nature. Characterization of magnetic solutions and nanoparticles by magnetic measurements, spectroscopy, diffractometry, small-angle X-ray diffraction, scanning probe microscopy, and others.Results. The term “water quantum material” refers to materials (micellar solutions) whose properties are mainly determined by the nuclear quantum effect on macroscopic scales (emergent property). Micellar solutions exhibit phenomena and functionality not always consistent with the classical theory of micellization. The article presents in detail the experimental results that suggest the manifestation of the emergent properties of magnetic materials obtained in aqueous micellar solutions of surfactants. In particular, Gd3+ ions in an aqueous micellar solution of sodium dodecyl sulfate exhibit paramagnetic properties, possibly indicating their random arrangement in solution contrary to the classical theory of micellization with an ordered adsorption layer on micelles. Hybrid Pt–Gd nanoparticles are formed in a quantum material with cetylpyridinium chloride as a matrix, although Gd3+ ions must be repelled by CP+ ions on micelles. Nanosized powders of cobalt ferrite and nickel ferrite obtained in a micellar solution of sodium dodecyl sulfate have superparamagnetic properties, although the presence of their precursor ions in the adsorption layer in classical micelles should lead to ferromagnetic properties.Conclusions. The synthesis of nanoparticles in a quantum material opens up the possibility of reducing ions of different signs in one stage during the processing of metallurgy waste, in order to obtain nanoparticles of various metals and their composites. Magnetic nanoparticles obtained in a quantum surfactant material self-assemble on various substrates, enabling the creation of materials whose residual magnetization and coercive field can be controlled at room temperatures.

Study of the electroosmotic flow of a structured fluid with a new generalized rheological model

The electroosmotic flow of a viscoelastic fluid in a capillary system was investigated analytically. The rheology of the fluid was characterized by a novel generalized exponential model equation. The charge density obeys the Boltzmann distribution, which governs the electrical double-layer field and body force generated by the applied electrical field. Mathematically, this scenario can be modeled by the Poisson-Boltzmann partial differential equation, by assuming that the zeta potential is small, i.e., less than 25 mV (Debye-Hückel approximation). Considering a pulsating electric field, the shear viscosity and the alteration in the volumetric flow were presented as a function of the material parameters through the characteristic dimensionless numbers by using an exponential-type generalized rheological model. Thixotropy, shear thinning, yield stress mechanisms, and weight concentration were analyzed through numerical results. Finally, the flow properties and rheology were predicted using experimental data reported elsewhere for worm-like micellar solution of cetyl trimethyl ammonium tosilate (CTAT). The rheological equation of state proposed in this study describes the alterations in the structure resulting from applied forces (tangential and normal). These forces induced a structural evolution (kinetic model) due to the relaxation processes caused by shear strain. It is important to mention that in electroosmotic flows, complex behavior such as (i) thixotropy, (ii) rheopexy, and (iii) shear banding flow is scarcely explained in terms of the change in the structure of the fluid under flow.Graphical

Bioinspired Nanotubes by Soft‐template Electropolymerization from Fully Conjugated Monomers

AbstractBioinspired by the strong water‐adhesive forces of gecko foot or rose petals, here, nanotubular structures are prepared by soft‐template electropolymerization. Water is mixed to a solvent of low water‐solubility to form a micellar solution in the presence of tetrabutylammonium perchlorate as the electrolyte and surfactant. As the monomer, a benzene is trifunctionalized with various thiophene and carbazole moieties. The monomers are fully conjugated to favor the deposition compared to polymerization, as confirmed by cyclic voltammetry experiments. The surface nanostructures (nanotubes, nano‐ribbons, coral‐like structures) are highly dependent on the monomer and the water content but less on the deposition method. The maximum water contact angle is 158.1° accompanied with strong water adhesive force. These surfaces are highly interesting for applications in water‐harvesting systems or in sensing platforms.

Comparative solubilization of Gliclazide in solutions of two anionic micelles with asymmetrical hydrophobic chain length: An experimental and theoretical analysis

Gliclazide (GCL) is used widely for reducing hyperglycemia in diabetic patients. It has poor solubility which leads to low oral bioavailability because of significant first-pass metabolism. In this work, we have employed two anionic micellar solutions of different hydrophobic chain lengths to solubilize GCL. They are sodiumtetradecyl sulfate (STS) and sodiumdodecyl sulfate (SDS). Our results reveal that longer hydrophobic chain was better suited for solubilizing GCL. The drug-surfactant interactions were assessed through FT-IR, conductivity, UV-Spectrophotometry, dynamic light scattering and antioxidant study. The results were compared with computational studies. There was negative free energy of micellization and positive entropy of micellization GCL + STS and GCL + SDS systems predicting spontaneity of the processes as calculated from the conductivity experiments. From the UV spectral studies, using Benesi-Hildebrand (B-H) equation, the binding constants demonstrated higher value for GCL + STS (0.286 M−1) compared to GCL + SDS (0.0231 M−1). The antioxidant properties of the above two combinations show that STS (93.14 %) has higher radical scavenging activity (RSA %) compared to SDS (77.45 %). Protein binding studies too indicated higher binding constant for STS than SDS with the drug. The docking model also supported the above findings. The longer hydrophobic chain length facilitated the solubilization of GCL with improved properties. This study offers a novel drug formulation for widely used drug GCL.

Primary amine citrate-based supramolecular designer solvent: Preconcentration of ochratoxin A for determination in foods by liquid chromatography

BackgroundSupramolecular solvents are nanostructured liquids that are separated from colloidal solutions of amphiphilic compounds as a result of self-assembly of amphiphiles and coacervation under changing conditions. They are considered to be designer solvents as their properties can be tailored to a specific analytical task by controlling the conditions of their formation (amphiphile, coacervation inducer, medium, concentration of components). The discovery of new extraction systems based on supramolecular solvents and their application to relevant analytical tasks are of great importance for the advancement of environmentally-friendly sample preparation. ResultsA novel green liquid-phase microextraction approach involving in situ formation of 1-octylamine citrate followed by preconcentration of ochratoxin A from aqueous extract of food sample in supramolecular solvent droplets was developed. The extraction system was carefully characterized. The density of the solvent allowed it to be to retrieved from the extraction system by its solidification. The alkaline nature of the obtained extract allowed the use of acetic acid for its dissolution instead of more toxic organic solvents followed by high-performance liquid chromatography with fluorometric detection. An excellent extraction recovery of 99 % and a satisfactory enrichment factor of 8.3 were achieved. The limit of detection was 0.5 μg kg−1, while the calibration plot was linear over the range of 1.5–50 μg kg−1. Cereal and roasted coffee bean samples were successfully analyzed with a relative bias less than 20 %. SignificanceIn the present work, a phenomenon of supramolecular solvent formation based on primary amine citrate was presented for the first time. Tetrabutylammonium bromide was investigated as a coacervation agent in an extraction system, and possible interactions responsible for its ability to induce phase separation in a micellar solution of primary amine citrate were described. The critical micelle concentration of 1-octylamine citrate in aqueous solution of tetrabutylammonium bromide was firstly determined.

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.

Micellar Solutions of PMMA-b-PNIPAM in Water/Methanol Mixtures: Effect of Temperature on the Micellar Size, Core–shell Structure, and Interaction

Micellar Solutions of PMMA-<i>b</i>-PNIPAM in Water/Methanol Mixtures: Effect of Temperature on the Micellar Size, Core–shell Structure, and Interaction

LOW TEMPERATURE ANALYTICAL CLOUD POINT EXTRACTION. 1: PROTOLYTIC PROPERTIES OF ACIDIC EXTRACTION INITIATORS IN ORGANIZED MEDIA

Cloud point extraction is a powerful tool for the analytical preconcentration of trace amounts of analytes. The standard cloud point extraction procedure requires prolonged heating of the solution, which is not always appropriate in the case of thermally unstable analytes or analytical forms and significantly limits the capabilities of the method. One of the ways to modify cloud point extraction is to find approaches to intensifying the process of analytical concentration. The main disadvantage of cloud point extraction is the need for thermal, ultrasonic, infrared or any other initiation of the formation of the surfactant-rich phase. The difficulty lies in the fact that such influence on the system is not always appropriate and possible, and can also negatively affect the formation of the target analytical form. The purpose of this work is to search for new initiators of cloud point extraction and justify the possibility of their analytical use. In the current paper, the ionization constants (pKa) of some cloud point extraction initiators such as aromatic carboxylic acids (benzoic, 4-chlorobenzoic, 3-nitrobenzoic, 2,4-dihydroxybenzoic, o-, m-, p-toluic and salicylic acids) in water and Triton X-100 micellar solutions at various concentrations of surfactant in the studied systems have been determined by the potentiometric titration method. It was found that the values of pKa of aromatic carboxylic acids (benzoic, 4-chlorobenzoic, 3-nitrobenzoic, 2,4-dihydroxybenzoic, o-, m-, p-toluic and salicylic acids) in water and Triton X‑100 micellar solutions naturally increase with increasing concentration of surfactant in the system. It is shown that the nature and the physico-chemical properties of the environment influence the nature and degree of change in the acid-base properties of the studied aromatic carboxylic acids (benzoic, 4-chlorobenzoic, 3-nitrobenzoic, 2,4-dihydroxybenzoic, o-, m-, p-toluic and salicylic acids). Criteria for the selection of cloud point extraction initiators are proposed, which allow analytical concentration to be carried out at room temperature.

Mesoscopic modeling of the effect of branching on the viscoelasticity of entangled wormlike micellar solutions

Mesoscopic modeling of the effect of branching on the viscoelasticity of entangled wormlike micellar solutions

Stochastic energetics of a colloidal particle trapped in a viscoelastic bath

We investigate the statistics of the fluctuations of the energy transfer between an overdamped Brownian particle, whose motion is confined by a stationary harmonic potential, and a surrounding viscoelastic fluid at constant temperature. We derive an analytical expression for the probability density function of the energy exchanged with the fluid over a finite time interval, which implicitly involves the friction memory kernel that encodes the coupling with such a non-Markovian environment, and reduces to the well known expression for the heat distribution in a viscous fluid. We show that, while the odd moments of this distribution are zero, the even moments can be explicitly expressed in terms of the autocorrelation function of the particle position, which generally exhibits a non-mono-exponential decay when the fluid bath is viscoelastic. Our results are verified by experimental measurements for an optically-trapped colloidal bead in semidilute micellar and polymer solutions, finding and excellent agreement for all time intervals over which the energy exchange takes place.

Phase diagrams and property of colloidal systems prepared with an alkyl polyglucoside surfactant and the essential oil of Melaleuca alternifolia (tea tree)

BackgroundThe purpose of this study was to develop the colloidal formulation, based on microemulsions and hydrogels, of Melaleuca alternifolia oil (aka tea tree oil, TTO) using a sustainable and biocompatible alkyl polyglucoside (APG) surfactant, Glucopon 600 CSUP (G600), commonly formulated for personal-care and home-care products. MethodsThe pseudo-ternary phase diagram of TTO-mixed surfactant-water was established with the water titration method at 25 °C. The mixed surfactants were composed of G600 and propylene glycol (PPG) as a co-surfactant at G600/PPG = 1/1, 2/1 and 3/1 (m/m). Colloid samples of one phase were further characterized with rheological measurements and dynamic light scattering (DLS) at 25 °C. Significant findingsThe samples containing TTO/mixed surfactant = 1/9 (m/m) and water show single phase only. With increasing water contents, the aforesaid system changed from Newtonian to pseudo-plastic, reflecting the transition from micellar solution / microemulsion to hydrogel. Especially, the gel-like behavior was confirmed with the dynamic oscillatory measurements, in which storage moduli were always larger than loss moduli at any time and any frequency under a constant strain of 0.5 %. Microemulsions made of 1 wt% tea tree oil and 9 wt% mixed surfactants were stable for > 1 month as monitored by aggregate size by DLS.

Highly sensitive and selective detection of nitrite using a fiber optofluidic laser.

Nitrite ion (NO2-) is a common contaminant that can significantly threaten human health and the environment. In this study, we demonstrate a chemical sensing platform to monitor the nitrite concentration using a fiber optofluidic laser (FOFL). An optical fiber, integrated into a microchannel, is used both as an optical micro-cavity and the sensing element. Rhodamine 6 G (Rh6G) in an aqueous micellar solution is used as the laser gain medium. The light intensity change of the lasing spectra is employed as an indicator for the NO2- ion concentration sensing. The lasing properties under different NO2- ion concentrations are experimentally and theoretically investigated to examine the sensing performance of the FOFL. The results show that the limit detection of the FOFL sensor is 0.54 µM, which is 2-order-of-magnitude lower than fluorescence measurement. The sensing mechanism of Rh6G for NO2- detection is studied by using density functional theory (DFT). The calculation results indicate that nitrite influences the electronic distribution of Rh6G based on the heavy atom effect, which leads to the fluorescence quenching of Rh6G in the excited state. In addition, the detection system exhibits favorable selectivity for NO2- ions.

Simple model for self-propulsion of microdroplets in surfactant solution.

We propose a simple active hydrodynamic model for the self-propulsion of a liquid droplet suspended in micellar solutions. The self-propulsion of the droplet occurs by spontaneous breaking of isotropic symmetry and is studied using both analytical and numerical methods. The emergence of self-propulsion arises from the slow dissolution of the inner fluid into the outer micellar solution as filled micelles. We propose that the surface generation of filled micelles is the dominant reason for the self-propulsion of the droplet. The flow instability is due to the Marangoni stress generated by the nonuniform distribution of the surfactant molecules on the droplet interface. In our model, the driving parameter of the instability is the excess surfactant concentration above the critical micellar concentration, which directly correlates with the experimental observations. We consider various low-order modes of flow instability and show that the first mode becomes unstable through a supercritical bifurcation and is the only mode contributing to the swimming of the droplet. The flow fields around the droplet for these modes and their combined effects are also discussed.

Impact of Leave-on Skin Care Products on the Preservation of Skin Microbiome: An Exploration of Ecobiological Approach.

Skincare products are used daily to maintain a healthy skin, although their skin microbiome impact is still poorly known. Preserving the natural resources and mechanisms of the skin ecosystem is essential, and a novel approach based on these premises, called ecobiology, has recently emerged in skincare. We evaluated the impact on the skin microbiome of three types of leave-on face skincare products: a hydrophilic solution, a micellar solution, and an oil-in-water emulsion. Samples for microbial profiling were obtained from 20 Caucasian females twenty-four hours and four days following daily application of the skincare products and compared to an untreated area. The bacterial diversity and the abundance of the skin microbiome were analyzed by 16S rRNA gene sequencing using an Illumina MiSeq platform. Our results confirmed the skin microbiome diversity and the prevalence of Cutibacterium spp. and Staphylococcus spp. at sebaceous sites. The bacterial diversity and abundance were not affected by the products, and no dissimilarities versus the control nor between each product were noted at both times. These preliminary results demonstrate for the first time that three types of leave-on face skincare products have no impact on the human skin microbiome and can be considered to be "microbiome friendly".

NEW CONCEPTS OF COLLOID SCIENCE: NANO-ADSORBENT AND PROTOMICELLE

Large molecules of dyes or other substances can play the role of a nano-adsorbent in aqueous surfactant solutions and, coated with surfactant molecules, resemble surfactant micelles with a solubilizate. Such micelle-like particles were called protomicelles. Their formation does not require a critical micelle concentration (CMC) and begins immediately when the surfactant is introduced into the solution. In this spectrophotometric study of Nile red (NR) in aqueous solutions of nonanoic acid (NOA), the case where protomicelles are more important than micelles is demonstrated for the first time. It has been shown that the solubilization of NR in both premicellar and micellar solutions proceeds through protomicelles rather than NOA micelles. The article also contains a theoretical part. In it, on the basis of the chemical potential of the nano-adsorbent, it is proved that the addition of a surfactant to a solution always increases the solubility of the nano-adsorbent. The dependence of adsorption on the curvature of the nano-adsorbent surface is considered and it is shown that the adsorption equations for flat surfaces can be used for curved surfaces with high accuracy.