Surfactant Research Articles

Study on the effects of inorganic salts and ionic surfactants on the wettability of coal based on the experimental and molecular dynamics investigations

Through the evaluation and preparation of a novel inorganic salt composite solution consisting of sodium dodecyl benzene sulfonate (SDBS), the nonionic surfactants polyethylene glycol pisooctyl phenyl ether (Triton X-100), and inorganic salt Na2SO4, based on surface tension, contact angle, settling time, wetting rate, and changes in the surface microstructure and functional groups of coal, this study analyzed the wetting behavior of the solution on coal dust and its adsorption capacity on the surface of coal particles. The results demonstrate that the composite solution of inorganic salts can significantly enhance the wettability of coal samples, reducing the contact angle to 21.54° and lowering the surface tension to 26.10 mN/m. After treatment with the solution, the relative content of oxygen-containing functional groups in the microscopic structure of the coal sample increased to 59.6 % and pores more prominent than 25 nm increased to 34.63 %. Molecular dynamics (MD) simulations of the water-inorganic salt composite solution-coal system are conducted using Materials Studio software, revealing that after the addition of the composite solution, the self-diffusion coefficient (D) of water molecules is 6.3 × 10-9 m2/s, the starting point of the composite solution is 15 Å, and the system's interaction energy increase to 14000 kcal/mol. It further elucidated the modification of the surface molecular structure of coal dust by the inorganic salt composite solution, increasing hydrogen bonds, enhancing wetting, and demonstrating a solid adsorption capability of the inorganic salt composite solution on the surface of coal dust.

Synergisms between Surfactants, Polymers, and Alcohols to Improve the Foamability of Mixed Systems

In order to produce detergents with improved performance and good market acceptability, it is crucial to develop formulations with improved foamability and cleaning performance. The use of a delicate balance of surfactants and additives is an appealing strategy to obtain good results and enables a reduction in the amount of chemicals used in formulations. Mixtures of hydrophobically modified linear polymers and surfactants, as well as balanced mixtures with co-surfactants and/or hydrotropes, are the most effective parameters to control foamability and foam stability. In the present study, the effect of the addition of hydrophobically modified linear polymers, nonionic co-surfactants and hydrotropes, and their mixtures to anionic and zwitterionic surfactant aqueous solutions was evaluated. It was found that the presence of the hydrophobically modified polymer (HM-P) prevented the bubbles from bursting, resulting in better stability of the foam formed using zwitterionic surfactant solutions. Also, the surfactant packing was inferred to be relevant to obtaining foamability. Mixtures of surfactants, in the presence of a co-surfactant or hydrotrope led, tendentially, to an increase in the critical packing parameter (CPP), resulting in higher foam volumes and lower surface tension for most of the studied systems. Additionally, it was observed that the good cleaning efficiency of the developed surfactant formulations obtained a higher level of fat solubilization compared to a widely used brand of commercial dishwashing detergent.

Biochemical characterization, stability, and kinetics of three substrates of the recombinant TMPRSS2 serine protease domain

Transmembrane serine protease 2 (TMPRSS2) is a membrane-bound protease belonging to the type II transmembrane serine protease (TTSP) family. It is a multidomain protein, including a serine protease domain responsible for its self-activation. The protein has been implicated as an oncogenic transcription factor and for its ability to cleave (prime) the SARS-CoV-2 spike protein. In order to characterize the TMPRSS2 biochemical properties, we expressed the serine protease domain (rTMPRSS2_SP) in Komagataella phaffii using the pPICZαA vector and purified it using immobilized metal affinity (Ni Sepharose™ excel) and size exclusion (Superdex 75) chromatography. We explored operational fluorescence resonance energy transfer FRET peptides as substrates. We chose the peptide Abz-QARK-(Dnp)-NH2 (Abz = ortho-aminobenzoic acid, the fluorescence donor, and Dnp = 2,4-dinitrophenyl, the quencher group) as a substrate to find the optimal conditions for maximum enzymatic activity. We found that metallic ions such as Ca2+ and Na+ increased enzymatic activity, but ionic surfactants and reducing agents decreased catalytic capacity. Finally, we determined the rTMPRSS2_SP stability for long-term storage. Altogether, our results represent the first comprehensive characterization of TMPRSS2’s biochemical properties, providing valuable insights into its serine protease domain.

Promote or inhibit turbulence drag reduction behavior of surfactant solutions with different micelle structures by certain nanoparticle addition

The micelle structure of surfactant is easy to be destroyed in the flow process resulting in a decrease in its drag reduction (DR) efficiency; therefore, how to strengthen the stability of the micelle structure during the flow process and thus improve the drag reduction efficiency deserves intensive research. In this work, by comparing a variety of nanoparticles, hydrophobic silica nanoparticles were selected as the best additive to enhance the turbulence drag reduction efficiency of surfactant solution with spherical micelle structure. The experimental results also demonstrated that the hydrophobic silica nanoparticles had a reinforcing effect on anionic, cationic, nonionic, and zwitterionic surfactant solutions with the same concentration (dominated by spherical micelles), and the optimal nanoparticle addition concentration and maximum drag reduction rate were obtained. Meanwhile, the effect of silica nanoparticles on the turbulence drag reduction efficiency of surfactant solutions with different micelle structures was evaluated by inducing the surfactant micelle structure change. It was shown that the hydrophobic silica nanoparticles had a strengthening effect on the turbulence drag reduction performance of surfactant solutions with spherical micelle structure, while they had an inhibiting effect on the turbulence drag reduction performance of surfactant solutions with worm-like micelle structure. The change in solution viscoelasticity indicated that the decrease in viscoelasticity was the main reason for the decrease in drag reduction efficiency of surfactant solution with worm-like micelle structure when silica nanoparticles were added. A mechanism for the interaction of hydrophilic/hydrophobic silica nanoparticles with spherical micelles and wormlike micelle structures was finally discussed and proposed.

Diffusiophoretic Transport of Charged Colloids in Ionic Surfactant Gradients Entirely below versus Entirely above the Critical Micelle Concentration.

When placed in an ionic surfactant gradient, charged colloids will undergo diffusiophoresis at a velocity, uDP = MDP∇ ln S, where MDP is the diffusiophoretic mobility and S is the surfactant concentration. The diffusiophoretic mobility depends in part on the charges and diffusivities of the surfactants and their counterions. Since micellization decreases surfactant diffusivity and alters charge distributions in a surfactant solution, MDP of charged colloids in ionic surfactant gradients may differ significantly when surfactant concentrations are above or below the critical micelle concentration (CMC). The role of micelles in driving diffusiophoresis is unclear, and a previously published model that accounts for micellization suggests the possibility of a change in the sign of MDP above the CMC [Warren, P. B.; . Soft Matter 2019, 15, 278-288]. In the current study, microfluidic channels were used to measure the transport of negatively charged polystyrene colloids in sodium dodecyl sulfate (SDS) surfactant gradients established at SDS concentrations that are either fully above or fully below the CMC. Interpretation of diffusiophoresis was aided by measurements of the colloid electrophoretic mobility as a function of SDS concentration. A numerical transport model incorporating the prior diffusiophoretic mobility model for ionic surfactant gradients was implemented to elucidate signatures of positive and negative diffusiophoretic mobilities and compare with experiments. The theoretically predicted sign of the diffusiophoretic mobility below the CMC was determined to be particularly sensitive to uncertainty in colloid and surfactant properties, while above the CMC, the mobility was consistently predicted to be positive in the SDS concentration range considered in the experiments conducted here. In contrast, experiments only showed signatures of a negative diffusiophoretic mobility for these negatively charged colloids with no change of sign. Colloid diffusiophoretic transport measured in micellar solutions was more extensive than that below the CMC with the same ∇ ln S.

Water-Based Bi2S3 Nano-Inks Obtained with Surfactant-Assisted Liquid Phase Exfoliation and Their Direct Processing into Thin Films

Bi2S3 has gained considerable attention as a semiconductor for its versatile functional properties, finding application across various fields, and liquid phase exfoliation (LPE) serves as a straightforward method to produce it in nano-form. Till now, the commonly used solvent for LPE has been N-Methyl-2-pyrrolidone, which is expensive, toxic and has a high boiling point. These limitations drive the search for more sustainable alternatives, with water being a promising option. Nonetheless, surfactants are necessary for LPE in water due to the hydrophobic nature of Bi2S3, and organic molecules with amphoteric characteristics are identified as suitable surfactants. However, systematic studies on the use of ionic surfactants in the LPE of Bi2S3 have remained scarce until now. In this work, we used sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS) and sodium hexadecyl sulfonate (SHS) as representative species and we present a comprehensive investigation into their effects on the LPE of Bi2S3. Through characterizations of the resulting products, we find that all surfactants effectively exfoliate Bi2S3 into few-layer species. Notably, SDBS demonstrates superior stabilization of the 2D layers compared to the other surfactants, while SHS becomes the most promising surfactant for obtaining products with high yield. Moreover, the resulting nano-inks are used for fabricating films using spray-coating, reaching a fine tuning of band gap by controlling the number of cycles, and paving the way for the utilization of 2D Bi2S3 in optoelectronic devices.

Exploring the impact of surfactant types and formulation variables on the EACN of crude and model oils

Characterizing the hydrophobicity of oils remains a significant challenge for the academic and industrial scientific communities, striving to optimize the formulation of Surfactant/Oil/Water (SOW) systems. Various descriptors, including the required Hydrophilic-Lipophilic Balance (required HLB) and the Equivalent Alkane Carbon Number (EACN), have been proposed to characterize oil hydrophobicity. Indeed, it is already known that the EACN of crude oils can be rapidly determined through dynamic Phase Inversion Temperature-induced (PIT) experiments. The study herein presents an alternative method to characterize the EACN of crude and model oils through dynamic Salinity-induced Phase Inversion (SPI) using two reference SOW systems, one with the ionic extended surfactant propyl heptyl propoxylated sodium sulfate (i-C3C7PO4SO4Na) and the other with the nonionic surfactant decyl tetraethylene glycol ether (C10EO4). Results reveal that the EACN of crude and model oils strongly depend not only on the chosen formulation variable but also on the nature of the surfactant. Discrepancies in EACN values for crude oils range between −0.2 and 3.3 units. These differences are justified by several factors: the segregation of the polar fraction for crude oils and its dependence with temperature, the high solubility of the nonionic surfactant in polar oils and the differing structures of both surfactants at the interface that changes the effective packing parameter of the system. When inversing a crude oil at high salinity conditions using temperature as formulation variable, a weighted average EACN value obtained with salinity from the two surfactants yields more realistic results than the EACN obtained from PIT. These findings found a direct application in the enhanced oil recovery field in which the attainment of ultra-low interfacial tension is essential to have an efficient crude oil desaturation.

A rare case of azathioprine induced anagen effluvium and plica neuropathica

Anagen effluvium is a type of hair loss that results from a sudden decrease in the metabolic activity of the hair follicle’s matrix cells. The condition is commonly associated with cancer treatments such as chemotherapy and radiation, but can also be caused by other factors. Plica neuropathica, on the other hand, is a condition where hair on the scalp becomes irreversibly matted. It is often linked to psychiatric disturbances, poor hair care, scalp infestations, and the use of ionic surfactants in shampoos. In rare cases, it has also been associated with certain medications. Here we present a rare case of a 16-year-old female who was on azathioprine and was diagnosed with an overlap of both conditions.

Effect of alcohol on synergistic interaction between amino sulfonate amphoteric surfactant and zwitterionic cocamidopropyl hydroxysultaine in aqueous solution

Micellization behavior for quasi-binary mixtures of an amino sulfonate amphoteric surfactant, sodium 3-(N-dodecyl ethylenediamino)-2-hydropropyl sulfonate (DES), with a zwitterionic surfactant cocamidopropyl hydroxysultaine (CAHS) both in water-glycerol and in water-glycol and the effect of alcohol were investigated using both the tensiometry and the conductometry. In the framework of regular solution theory and based on the pseudophase separation model, the Rubingh’s model, the Rodenas’ model and the Clint’s model were adopted to successfully estimate the related micellar and thermodynamic parameters. The synergistic interaction between DES and CAHS along with the nonideal mixing are observed in the entire range of mixing. Besides the hydrophobic effect, the compatibility in molecular conformation, the steric hindrance, the feeble electrostatic repulsion, the interaction between dipoles and the formation of hydrogen bond can account for the dependence of the mixed critical micelle concentration and the micellar composition on the content in bulk solution. In comparison with the case of glycerol, the presence of glycol partly disfavors the micellization process. Thermodynamic parameters show that the entropy makes an overwhelming contribution to the spontaneous micellization process, the release of mixing heat promotes the formation of stably mixed micelle, the greater share of entropy in the presence of glycol than in the presence of glycerol displays the disadvantage in the micellization process as well as the dependence of both the free energy change and the share of entropy on the mixing ratio in bulk solution is approximately symmetric with respect to about 0.500.

Synergistic effects of different ionic surfactants and temperature on rheological behavior and air-void structure of cement mortar

The influence of air entrainment on rheological behavior of fresh cementitious materials has attracted a lot of attention in the past years, but the results are still in controversy. In this research, cement mortars were prepared with equivalent air contents using different air-entraining admixtures (AEAs) to measure their fresh-state performance and hardened air-void system at variable temperature conditions, which aimed to clarify and unveil the coupled effects of different surfactants and temperature for the first time. The adsorption amount of AEA, zeta potential of cement, along with hydration kinetics of mixtures were evaluated to characterize the interaction of air bubbles with cement grains. It was found that for mixture without superplasticizer (SP), the impact of air entrainment on rheological parameters was dependent on the interaction intensity of AEA molecules with cement. For SP-plasticized mixture, air entrainment tended to cause a shear-thinning behavior with decreased plastic viscosity, while its influence on yield stress was in accordance with the situation without SP. The hardened samples with anionic surfactant contained more small voids and lacked big voids, whereas the samples with cationic surfactant showed opposite outcomes. With temperature decreasing, both the average chord length and the spacing factor of air voids increased owing to the reduced yield stress of mixture. The results will provide in-depth illustrations for understanding how air bubbles change the rheological behavior of mixture, and more importantly it will explain the seemingly inconsistent findings reported by previous literatures.

Influence of typical liquid fuels on foam properties of critical components of environmentally friendly aqueous film-forming foams

In this study, the influence mechanism of typical fuels (oils) on the foam properties of mixture of hydrocarbon and fluorocarbon surfactants was investigated. A mixed solution was prepared based on a nonionic hydrocarbon surfactant (APG-0810) and a zwitterionic C6 fluorocarbon surfactant (short-chain). The effect of different oils (heptane, kerosene, diesel, and transformer oil) on the physical property parameters, foamability, oil resistivity of foam and single vertical liquid film of the mixture are systematically investigated. Results indicate that the viscosity of mixture increases, but the conductivity, surface activity, and initial foam height decreases with addition of the four oils. The drainage and volume decay of the foam are accelerated by the presence of oils. In addition, the presence of oils accelerates liquid film thinning through affecting drainage, especially for the oil with higher density, water solubility, and volatility. The four oils showed different effect on foam properties due to the difference in nature and emulsification of them. Among them, the foam properties under the action of heptane is the best, and the oil resistivity of foams is the best. This study can provide theoretical guidance for oil resistivity of hydrocarbon and fluorocarbon surfactant stabilized foams.

Effect of Electrostatic Interactions in Wormlike Micelles of Surfactants Based on Betaine and Charged Tertiary Amine with the Same Hydrophobic Groups

The viscoelastic properties and structure of solutions of mixed wormlike micelles based on a zwitterionic surfactant, oleylamidopropyldimethylcarboxybetaine (OAPB), and positively charged oleylamidopropyldimethylamine (OAPA) have been studied at different ratios between the components. At a small fraction of the cationic surfactant, OAPA, the solution exhibits viscoelastic properties characteristic of semidiluted solutions of entangled wormlike micelles, the presence of which has been confirmed by cryogenic electron microscopy data. It has been found that, as the molar fraction of the charged surfactant increases to 0.1, the viscosity and relaxation time of the solutions decrease by a factor of three, and the values of the storage modulus remain unchanged at short stress action times. The studied surfactants have a similar structure; therefore, when replacing zwitterionic OAPB molecules by positively charged OAPA molecules, the main factor of variations in the properties and structure is the enhancement of the electrostatic repulsion on the micelle surface. It has been shown that this factor leads to a decrease in the average length of micelles and an increase in their number, which have a weak effect on the rheological properties of the system as long as the length of the micelles is larger than the length of the subchains in the network. With an increase in the molar fraction of OAPA from 0.1 to 0.5, the viscosity and relaxation time drop drastically by several orders of magnitude and the viscoelastic response of the solution is lost; i.e., the network is destroyed. This transition from a semidilute solution to a dilute one is explained by a decrease in the length of the wormlike micelles and the formation of spherical ones. Cryogenic electron microscopy images have confirmed the formation of a mixture of long and short wormlike micelles with spherical micelles at an OAPA molar fraction of 0.5.

Electrical conductivity of nanofluids with single- and multi-walled carbon nanotubes. Experimental study

The object of this paper is to experimental study the electrical conductivity of nanofluids with carbon nanotubes (CNT). Nanofluids based on water, ethylene glycol and isopropyl alcohol with single-walled (SWCNT) and multi-walled (MWCNT) carbon nanotubes are considered. In some cases, surfactants were used to prepare the nanofluid. CNT concentrations varied from 0.05% to 1%. It was shown that the electrical conductivity of all nanofluids much more than that of base fluids. The influence of surfactants on the electrical conductivity of nanofluids is studied and analyzed. The use of surfactants in all cases increases the electrical conductivity of the initial base fluids. The greatest excess of the electrical conductivity was achieved when using ionic surfactants. For the first time, the electrical conductivity of nanofluids with SWCNTs and MWCNTs is systematically compared. The same base fluids are used for this. It was shown that electrical conductivity of nanofluids with SWCNTs significantly exceeds that of nanofluids with MWCNTs. The effect of aspect ratio on electrical conductivity of nanofluids with SWCNTs and MWCNTs are studied. In conclusion, the possible mechanisms of electrical conductivity of the considered nanofluids are discussed.

One-Pot synthesis and interfacial activity of imidazolium ionic liquid surfactants with double-chain hydrophobic

Three double-chain imidazolium ionic liquid surfactants (ILS) with varying alkyl lengths, namely [C10mimC10][OAc], [C12mimC12][OAc], and [C14mimC14][OAc], were synthesized via the one-step Debus-Radziszewskireaction. The chemical structures of these three ILS were confirmed through FT-IR, 1H NMR and ESI-MS analyses. Their surface/interface activity, wetting ability, thermal stability, and aggregation properties were investigated. The results indicated that the presence of double-chain hydrophobic groups in ILS exerted a significant influence on their surface/interface activity. Surface activity and micellization properties were assessed using surface tension measurements, revealing that the micellization process of double-chain ILS was more favorable compared to single-chain ILS. Among the three ILS examined, [C14mimC14][OAc] exhibited the lowest surface tension and critical micelle concentration (CMC) values, measuring 29.07 mN/m and 1.64 × 10-2 mmol/L, respectively. Solutions containing approximately 50 ppm of these ILS could reduce interfacial tension to below 1 mN/m. Additionally, the contact angle decreased to less than 90° within 90 s. The formation of aggregates in aqueous solutions was found to be influenced by the number of CH2 units present in the different ILS molecules.

Shielding Effects Provide a Dominant Mechanism in J-Aggregation-Induced Photoluminescence Enhancement of Carbon Nanotubes.

The unique photophysical properties of single-walled carbon nanotubes (SWCNTs) exhibit great potential for bioimaging applications. This led to extensive exploration of photosensitization methods to improve their faint shortwave infrared (SWIR) photoluminescence. Here, we report the mechanisms of SWCNT-assisted J-aggregation of cyanine dyes and the associated photoluminescence enhancement of SWCNTs in the SWIR spectral region. Surprisingly, we found that excitation energy transfer between the cyanine dyes and SWCNTs makes a negligible contribution to the overall photoluminescence enhancement. Instead, the shielding of SWCNTs from the surrounding water molecules through hydrogen bond-assisted macromolecular reorganization of ionic surfactants triggered by counterions and the physisorption of the dye molecules on the side walls of SWCNTs play a primary role in the photoluminescence enhancement of SWCNTs. We observed 2 orders of magnitude photoluminescence enhancement of SWCNTs by optimizing these factors. Our findings suggest that the proper shielding of SWCNTs is the critical factor for their photoluminescence enhancement, which has important implications for their application as imaging agents in biological settings.

Experimental study of adsorption/desorption and enhanced recovery of shale oil and gas by zwitterionic surfactants

Shale reservoirs have the characteristics of low permeability and low porosity. In order to enhance the recovery of shale oil and gas, surfactant flooding is a mature reservoir oil recovery method. However, the adsorption of different surfactants on the reservoir rock surface is restricted, depending on the type of surfactant. Therefore, a zwitterionic surfactant (OPHS) was synthesized from oleic acid, 3-dimethylaminopropylamine and sodium 3-chloro-2hydroxypropanesulfonate, and characterized by FTIR, 1H NMR, and TGA, and the mechanism of the OPHS for enhancing oil and gas recovery on shale surfaces was investigated. The results showed that the critical micelle concentration (CMC) of OPHS surfactant solution is 7.9 × 10-4 mol/L and the γCMC is 27.5 mN/m; the concentration of 0.1 % OPHS surfactant solution could reduce the contact angle of the cores from 127.2° to 38.8°, which resulted in spontaneous imbibition; The absolute Zeta potential of shale particles in the OPHS surfactant solution was measured at 39 mV, whereas in deionized water at 15.3 mV. This difference can be attributed to the formation of a stable hydration film on the surface of shale particles induced by the wetting reversal effect. Spontaneous imbibition experiments showed that a 0.1 % solution of OPHS surfactant was able to increase the recovery rate by more than four times compared to the imbibition solution without added surfactant; In high-pressure gas adsorption/desorption experiments, the OPHS surfactant solution demonstrated a higher affinity for adsorption onto the shale surface. It effectively occupied adsorption sites, ultimately facilitating methane gas desorption from the shale. In summary, OPHS zwitterionic surfactants exhibit the capability to desorb hydrocarbons from shale pores through mechanisms such as wetting reversal and competitive adsorption. This research holds significant potential for advancing the field of shale oil and gas recovery, providing valuable insights for enhancing recovery processes.

Insights into the role of ionic surfactants on the morphology of gold and gold@silver nanoparticles

Cyanidin-3, 5-di-O-glycoside (anthocyanin) was extracted from the red rose flower petals in an aqueous media. Anthocyanin was used as reductant to the preparation of gold nanoparticles with cationic and anionic surfactants. UV–visible absorption spectroscope, transmission electron microscope, scanning electron microscope, and energy dispersive X-ray spectroscope were employed to determine absorption bands of anthocyanin, surface Plasmon resonance (SPR) band, and morphology of the gold and gold@silver nanoparticles. Anthocyanin exhibited two absorption peaks at 284 and 518 nm, and one shoulder at 328 nm in the UV–visible spectrum. The intensity of these peaks decreases with time after the addition of HAuCl4. The color and the position of SPR band of gold nanoparticles depend on the concentration of gold salt with and without cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). The anionic and cationic head groups of SDS and CTAB micelles have significant impact of the morphology of gold nanoparticles. Seedless co-reduction method was used for the synthesis of gold@silver nanoparticles. TEM images clearly indicate the formation of bimetallic gold@silver core-shell nanoparticles. The antioxidant power of AuNPs and gold@silver nanoparticles were tested in terms of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity as a function of different concentrations of nanoparticles.

Drug-induced transitions from micelles to vesicles in ionic surfactant solutions

Surfactant solutions play key roles in scientific research and technological applications. Here we investigated solutions that combined an ionic surfactant, Cetylpyridinium Chloride (CPyCl), with a non-steroidal, anti-inflammatory drug, Sodium Diclofenac (Diclo). The study covered a wide range of compositions and utilized both rheology and cryogenic-Electron Microscopy (cryo-EM). The solutions were prepared at three different concentrations of CPyCl: 5.0 mM, 16.7 mM and 33.0 mM, and we maintained the ratio of surfactant to salt, R=CPyCl/Diclo, within the range of 0.24<R<1.2. Linear viscoelasticity was measured at 25°C. The use of dilute solutions allowed for detailed cryo-EM imaging. By tracking the evolution of the zero-frequency viscosity as a function of Diclo concentration, we identified distinct regions of different rheological responses. The correlation between frequency sweep data and cryo-EM images enabled us to link these regions to specific morphological transitions ranging from spherical micelles to long and entangled wormlike micelles, to branched networks and, eventually, to perforated vesicles. For some systems, we were able to measure the complete spectrum of relaxation times, including the shortest characteristic Rouse time at high frequencies, previously only achieved by Diffusive Wave Spectroscopy. The use of existing models to evaluate the relevant important microstructural parameters such as entanglement, contour, and persistence lengths allowed us to establish a clear correlation between the microstructural parameters derived through rheology and the insights from the cryo-EM analysis.

Molecular interaction of nonsteroidal anti‐inflammatory prodrug nepafenac with ionic surfactants

AbstractDrug‐surfactant interaction increases the solubility of poorly water‐soluble drugs and design better pharmaceutical formulations. The degree of interaction of nepafenac (NP), a nonsteroidal anti‐inflammatory prodrug was studied with ionic surfactant molecules such as cationic surfactant cetrytrimethyl ammonium bromide (CTAB) and anionic surfactant sodium dodecyl sulphate (SDS) in an aqueous medium at room temperature. NP made mixed micelles with CTAB and SDS. To investigate the influence of interactions, conductivity measurements, UV–visible spectroscopy, and fluorescence measurements were recorded. The quantification of NP–surfactant interactions was investigated using various mathematical models. The CMC values determined from conductivity measurements of pure surfactants were 0.96 mM for CTAB and 8.14 mM for SDS near to their literature values. At different mole fractions of NP in UV measurements, binding constants from lnKb were found 0.025 and 0.123 and number of NP molecules per micelles (n) 67, 46 for CTAB and SDS, respectively. The mixed micelles of NP–CTAB and NP–SDS revealed that CTAB has a strong interaction with NP than SDS. The Benesi–Hildebrand relationship, Stern–Volmer and Kawamura replica for the partition coefficient were used to confirm the findings. We are confident that the host–guest interaction mechanism can contribute to a better understanding of molecular recognition in the phospholipid membrane model.

Insights into the Efficient Release of the Polyacrylamide Drag Reducer via a pH-Responsive Inverse Polymer Emulsion.

The enormous demand for petroleum consumption has resulted in the shortage of fossil resources, prompting the need to explore unconventional reservoirs. Polyacrylamide emulsion drag reducers are capable of inhibiting the turbulence of fracturing fluids for enhancing the reservoir stimulation results, but the poor dissolution efficiency of polyacrylamide emulsion drag reducers is the primary limitation to their large-scale application. Here, a pH-responsive ionic liquid surfactant, oleic acid/cyclohexanediamine (HOA/HMDA), is synthesized by using oleic acid (HOA) and cyclohexanediamine (HMDA). HOA/HMDA shows a remarkable pH-responsive behavior due to the pH-induced deconstruction of the HOA/HMDA structure. Interestingly, the HOA/HMDA-stabilized monomer emulsion exhibits an obvious pH-induced emulsion structure transformation behavior. In addition, the HOA/HMDA-stabilized monomer emulsion possesses excellent dynamic and storage stability, supporting the inverse emulsion polymerization of the polymer P(AM/AMPS/AA). The obtained P(AM/AMPS/AA) polymer inverse emulsions maintained stability for 30 days. Our finding proposes that the structure of the P(AM/AMPS/AA) polymer inverse emulsions changes with pH stimulation, which is capable of facilitating the release of polymers. P(AM/AMPS/AA) is released from the P(AM/AMPS/AA) polymer inverse emulsions within 30 s at a pH value of 12.06, along with a drag reduction rate of 62.54%. Obviously, the HOA/HMDA-stabilized P(AM/AMPS/AA) polymer inverse emulsions eliminate the contradiction between the stability and release of polyacrylamide emulsion drag reducers, which is promising for meeting the demands of reservoir stimulation.