Hydrophilic Chain Length Research Articles

Hydrophilic Chain Length for Octylphenol Polyoxyethylene Ether Adsorption at the n-Hexadecane-Water Interface: Theoretical and Experimental Study.

With the advancement of technologies for developing tight and shale reservoirs, nonionic surfactants have garnered significant attention due to their remarkable properties. The structure of these surfactants plays a crucial role in determining the characteristics of the oil-water interface, particularly influencing emulsification behavior and crude oil recovery. This study investigates the effect of varying the number of hydrophilic polar groups (n = 10, 20, 30, 50) in octylphenol polyoxyethylene ether (OP-n) on its adsorption behavior at the n-hexadecane-water interface using molecular dynamics simulation. The impact of these variations on interfacial properties was further analyzed through measurements of interfacial tension and observations of emulsion droplet morphology. The study results indicate that variations in the number of hydrophilic polar groups significantly affect interfacial properties. Increasing the number of hydrophilic polar groups led to a notable increase in the thickness of the n-hexadecane or water phase, as well as the thickness of the water or oil layer and the surfactant layer. Moreover, when the number of hydrophilic polar groups reached 20, the OP-n molecules exhibited a more curled conformation at the interface, enhancing their ability to encapsulate water and resulting in a decrease in the diffusion coefficient of the molecules in each phase. Additionally, interfacial tension was found to be positively correlated with the number of hydrophilic polar groups and remained unchanged beyond a certain emulsion diameter. This study provides a theoretical basis and reference data for optimizing surfactant structures to improve crude oil recovery.

Synthesis of perylene‐PEO hyperdispersants for aqueous graphene dispersion

AbstractGraphene, with excellent thermal conductivity, electrical and corrosion shielding performance has great application potential in the fields of heat dissipation coating, conductive agent and anticorrosion composite coatings. However, due to its large specific surface area, resulting strong aggregation behavior limits its application. Herein, the hyperdispersants with perylene anchoring groups are synthesized through the amidation coupling reaction between diacid anhydride and polyetheramine. The branching degree and length of hydrophilic chains on hyperdispersant are revealed to be the very important factors to affect the dispersion stability of aqueous graphene dispersion. The hyperdispersant with a single hydrophilic chain and the molecular weight 2000 of polyetheramine has the excellent dispersal activity discovered by Rheology, particle size distribution and Raman measurements. The possible mechanism is the strongest anchoring effect of perylene on graphene surface and thus achieving in best effective spatial exclusion stabilization effect of hydrophilic chains.

Effect of polyoxyethylene laurate series surfactants on HCFC-141b hydrate formation

To address the problems of slow crystallization and nucleation in two-phase miscibility in the application of refrigerant hydrates, adding surfactants can be taken as an effective way to promote hydrate formation. Three kinds of polyoxyethylene laurate (LAE) surfactant with different hydrophilic chain lengths (LAE-4, LAE-9 and LAE-24) were selected as accelerators to study their effects on hydrate formation. LAE series surfactants significantly reduce hydrate nucleation induction time. The hydrate induction time of the system with 4.0 wt% LAE-9 is shortest (98 min). The hydrate formation with 4.0 wt% LAE-9 has small randomness and is more stable. Micelles formed by LAE surfactants provide more nucleation sites and accelerate hydrate growth. The hydrate cold storage density is related to the hydrophilic chain length of surfactant. The system with 4.0 wt% LAE-9, which has a suitable hydrophilic chain length, achieves the largest hydrate cold storage density (246.10 kJ·kg−1). Hydrate has the fastest growth rate of 4.80 kJ·kg−1·min−1 in the system with 2.0 wt% LAE-24. There is a “memory” effect during hydrate formation and dissociation cycle, eliminating the need for induction time during hydrate re-formation. Hydrate can be re-formed quickly.

Tailoring Waterborne Coating Rheology with Hydrophobically Modified Ethoxylated Urethanes (HEURs): Molecular Architecture Insights Supported by CG-MD Simulations.

A novel investigation of the effects of the hydrophilic and hydrophobic segments of hydrophobically modified ethoxylated urethanes (HEURs) on the rheological properties of their aqueous solutions, latex-based emulsions, and waterborne paints is demonstrated. Different HEUR thickeners were produced by varying the poly(ethylene glycol) (PEG) molecular weight and terminal hydrophobic size. Results reveal that the strength of hydrophobic associations and, consequently, the rheological properties of HEUR formulations can be effectively controlled by modifying the structure of the hydrophobic segment, specifically, the combination of diisocyanate and monoalcohol. This allows for the on-demand attainment of diverse rheological behaviors ranging from predominantly Newtonian profiles exhibiting lower viscosities to markedly pseudoplastic behaviors with significantly higher viscosities. The length of the hydrophilic group appears to affect viscosity only marginally up to a molecular weight of 23,000 g/mol, with more notable effects at 33,000 g/mol. Additionally, it was indicated that the rheological responses observed in water solutions provide a reliable forecast of their behavior in latex-based emulsions and waterborne paints. Coarse-grained molecular dynamics (CG-MD) simulations were also applied to gain insight into HEUR micelle dynamics in aqueous solutions. Guided by the DBSCAN algorithm, the simulations successfully captured the concentration-dependent behavior and the impact of hydrophilic chain length, aligning with the experimental viscosity trends. Various metrics were employed to provide a comprehensive analysis of the micellization process, including the hydrophobic cluster volume, the total micellar volume, the aggregation number, and the number of chains interconnecting with other micelles.

Heat transfer enhancement and long-term test of non-ionic Triton surfactant with different hydrophilic chain lengths

Surfactant aids boiling enhancement, but the related mechanism is not yet comprehensively understood. For mechanism investigation on surfactant molecule, most of existing studies focused on its hydrophobic part, while research on hydrophilic part is scarce. In this paper, a group of non-ionic Triton surfactants with same functional group but different hydrophilic chain lengths were experimentally tested for pool boiling on flat copper. At critical micelle concentration (CMC), long-chain Tx-405 exhibited higher heat transfer coefficient (97.4 kW/(m2·K)) than Tx-100 (77.1 kW/(m2·K)) and Tx-114 (77.4 kW/(m2·K)). Long-term test indicated a gradually deteriorating trend of heat transfer performance from days on. Solution properties and bubble dynamics were measured. At low concentration, surfactant with shorter hydrophilic chain has better heat transfer performance due to greater surface tension reduction. The increase of hydrophilic chain length improves water affinity of surfactant and thus leads to higher CMC. If there is no restriction for surfactant concentration, a longer hydrophilic chain is favorable for higher heat transfer coefficient at CMC. The results in this paper provide insights for mechanism investigation on surfactant, promote further design of new surfactant, and contribute to the prediction of heat transfer enhancement effect.

Self-Assembled Metal-Coordination Nanohelices as Efficient and Robust Chiral Supramolecular Catalysts for Enantioselective Reactions.

The development of chiral nanostructures-based supramolecular catalysts with satisfied enantioselectivity remains a significantly more challenging task. Herein, the synthesis and self-assembly of various amino acid amphiphiles as chiral supramolecular catalysts after metal ion coordination is reported and systematically investigate their enantioselectivity in asymmetric Diels-Alder reactions. In particular, the self-assembly of l/d-phenylglycine-based amphiphiles (l/d-PhgC16) and Cu(II) into chiral supramolecular catalysts in the methanol/water solution mixture is described, which features the interesting M/P nanohelices (diameter ≈8nm) and mostly well-aligned M/P nanoribbons (NRs). The M/P supramolecular catalysts show both high but inverse enantioselectivity (>90% ee) in Diels-Alder reactions, while their monomeric counterparts display nearly racemic products. Analysis of the catalytic results suggests the outstanding enantioselectivities are closely related to the specific stereochemical microenvironment provided by the arrangement of the amphiphiles in the supramolecular assembly. Based on the experimental evidence of chirality transfer from supramolecular nanohelices to coordinated Cu(II) and substrate aza-chalcone and the molecular dynamics simulations, the enantioselective catalytic mechanisms are proposed. Moreover, the relationships between molecular structures of amino acid amphiphiles (the hydrophilic head group and hydrophobic alkyl chain length) in supramolecular catalysts and enantioselectivity in Diels-Alder reactions are elaborated.

Effect of hydrophilic chain length on the impact and wetting behavior of nonionic surfactants regulating droplets on hydrophobic surfaces

Regulation of the droplet impact and wetting behavior of hydrophobic surfaces is a difficult problem to solve. The addition of surfactants is commonly used to improve droplet retention by modifying interfacial properties. The effect of the surfactant structure on the regulation of droplet rebound and wetting behavior needs further research. In this study, the physicochemical properties and regulation of droplet behavior for nonionic surfactants with different hydrophilic chain lengths were investigated. The results indicate that with an increasing hydrophilic chain (Epoxyethane (EO) numbers) length, Isodecyl polyoxyethylene ether (XL) surfactant solutions could better regulate the droplet impact behavior on hydrophobic surfaces and better suppress droplet rebound. This mainly attributed to a faster diffusion of surfactant molecules to newly formed interfaces, thus leading to better wetting reversal and deposition of substrates. Additionally, it was found that with the reduction of the hydrophilic chain length, XL surfactant solutions could better regulate droplet wetting, mainly attributed to its critical micelle concentration and surface tension, creating greater Marangoni forces during spreading and leading to faster spreading rates and larger spreading areas. The results from this study promote understanding of the mechanism for regulation of impact behavior and surfactant solution wetting on hydrophobic surfaces by regulating the EO chain length. This provides an effective strategy in regulating droplet deposition on hydrophobic surfaces and provides the basic data or guidance for the use of nonionic surfactants as tank-mixing adjuvants in unmanned aerial vehicle plant protection.

Molecular selection and environmental evaluation of eco-friendly surfactants to efficiently reduce pesticide pollution

Surfactants are widely used in industrial and agricultural production, especially as agrochemicals. However, the improvement of pesticide utilization by surfactants as the synergist should be achieved without adverse effects on crops, non-target organisms and related ecological environment, which is a lack of attention. Herein, the influence of the nonionic surfactant Triton X (TX) series with different hydrophilic chain lengths on the “Pesticide-Crop-Ecology” system was systematically studied. The impact behavior of TX droplets on the scallion leaf surface was predicted first by molecular dynamics (MD) simulation. Then the impact behavior, adhesion properties and foliar retention of TX droplets on the scallion leaf were investigated by physical experiments. The results showed that the TX-102 structure could increase leaf retention of pyraclostrobin (PYR) by 15.66% due to its fast molecular migration rate, strong adhesion and appropriate wettability with leaves. Furthermore, the environmental effect of the selected TX-102 was fully evaluated, and it was found that TX-102 was relatively safe for both Vicia faba cells and human 293t cells, although it slightly promoted the effect of PYR on cell apoptosis. Importantly, TX-102 has a potential repair effect on the damage to dominant soil bacteria caused by PYR. This study provides a new strategy for the development of efficient and environment-friendly pesticide synergists and sustainable agricultural development.

Amphiphilic block copolymers as dual flocculation-flotation agents for rapid solid–liquid separation of radioactive wastes

The potential of poly(acrylic acid)-b-poly(n-butyl acrylate) as a dual flocculant-collector in combined flotation-sedimentation dewatering operations was investigated. The amphiphilic block copolymers were synthesised with consistent hydrophilic chain lengths and varying hydrophobic chain lengths. Various techniques were employed to analyse polymer behaviour at the air–water interface, being interfacial surface tension and dilational viscoelasticity. Polymer adsorption onto Mg(OH)2 was determined differentially using UV–Vis spectroscopy. Floc structures were determined using static light scattering, and flocculation-flotation performance was analysed using settling tests and flotation cell material balances. Results showed that longer hydrophobic chains were less surface-active, reducing foamability and water entrainment. The unimer-micellar adsorption transition points were identified through viscoelastic properties and particle adsorption studies. A distinct change in floc density and structure was observed for the largest molecular weight copolymer when the dosed concentration increased into the micellar adsorption region, suggesting a pseudo-bridging flocculation mechanism. Settling rates were significantly higher for particles flocculated with the larger molecular weight polymer, correlating to their larger aggregate sizes, especially over the micellar transition point. The largest molecular weight block copolymer demonstrated superior collection efficiency compared to the traditional surfactant, sodium dodecylsulfate (SDS), below its micellar adsorption transition point. However, beyond this point, the lack of exposed hydrophobic blocks hindered the hydrophobisation of Mg(OH)2 particles, reducing collection efficiency. Comparing flotation cell particle size distributions, it was suggested that recovery may be hydrodynamically hindered by the largest floc sizes, though recovery was observed for particles in the order of < 600 μm.

Influence of Hydrophobic and Hydrophilic Chain Length of CiEj Surfactants on the Solubilization of Active Pharmaceutical Ingredients.

Up to 90% of all newly developed active pharmaceutical ingredients (APIs) are poorly water soluble, most likely also showing a low oral bioavailability. In order to increase the aqueous solubility of these APIs, surfactants are promising excipients to increase both solubility and consequently bioavailability (e.g., in lipid- and surfactant-based drug delivery systems). In this work, we investigated the influence of hydrophobic and hydrophilic chain lengths of CiEj surfactants (C8E6, C10E6, and C10E8) toward the solubilization of fenofibrate, naproxen, and lidocaine. Furthermore, we investigated the partitioning of these APIs between the surfactant aggregates and the surrounding aqueous bulk phase. For all APIs considered, we determined the locus of API solubilization as well as the individual aggregation numbers (Nagg) of surfactants and API molecules in an API/surfactant aggregate. We further determined the hydrodynamic radius (Rh) of the API/surfactant aggregates in the absence and presence of the APIs. The size of the API/surfactant aggregates (Nagg, Rh) passes through a minimum upon lidocaine solubilization; it gradually increases upon naproxen solubilization and is almost constant upon fenofibrate solubilization. The results give valuable insights into the solubilization mechanisms of APIs in the CiEj surfactant aggregates. Our results reveal that fenofibrate is solely solubilized in the hydrophobic core of the CiEj surfactant aggregates, as only the hydrophobic chain length of the surfactant influences its solubilization. Naproxen is solubilized in the palisade layer of the surfactant aggregates, as both the hydrophobic and hydrophilic chain lengths are decisive for its solubilization. Lidocaine is mainly solubilized in the rather hydrophilic corona region of the surfactant aggregates, as the hydrophilic chain length of the surfactant governs its solubilization. The results further reveal that the hydrophilic/lipophilic balance is not an appropriate measure to estimate the solubilization capacity of surfactant aggregates.

Synthesis and characterization of carbohydrate-based biosurfactant mimetics

Glycolipid biosurfactants are of interest for various industry sectors. We report the synthesis and characterization of enantiopure poly-amido-saccharides (PASs) containing myristoyl (C14), palmitoyl (C16), or stearoyl (C18) terminal chain lengths as mimetics of glycolipid biosurfactants. These amphiphilic polymers are water soluble, adopt a helical secondary structure, decompose at temperatures greater than 240 °C, are non-cytotoxic, and self-assemble into nanostructures. Polymers containing the shorter hydrophilic chain lengths and the hydrophobic C14 chain exhibit the lowest surface tension among all polymers.

Preparation of Epoxy Resin Emulsifiers with Different Structures and a Comparative Study of their Properties

AbstractThe structure of epoxy resin emulsifier has important influence on the stability of epoxy resin emulsion/dispersion. However, there is no systematic comparative study so far about the effect of the structure of the epoxy resin emulsifier on their physiochemical properties and performance. In this work, two types of linear (AB and ABA types) and one type of branched epoxy resin emulsifiers were prepared by using bisphenol A epoxy resin E‐44 as the hydrophobic chain segment A and polyethylene glycol (PEG) as the hydrophilic chain segment B, and their physicochemical properties were compared. It has been found that the branched epoxy resin emulsifier is more hydrophilic than the two kinds of linear epoxy resin emulsifiers as a result of higher content of hydrophilic PEG chains. More importantly, the solubilization ability of the branched epoxy resin emulsifier to toluene is much higher than that of the two linear epoxy resin emulsifiers and exhibits an unique behavior, i. e., it increases monotonically with increasing hydrophilic PEG chain length. This work shed a light on the structural importance of epoxy resin emulsifier on its physicochemical properties and may provide a better choice of emulsifiers for the preparation of stable epoxy resin emulsions/dispersions.

Interfacial performance of cationic, anionic and non-ionic surfactants; effect of different characteristics of crude oil

In this study, the performance of a large number of anionic (SDS, SLS, and SDBS), cationic (CTAB), and non-ionic (Triton X-100 and Tween 80) surfactants on the surface activity, emulsion size, and surface charge of five oil samples was investigated in aqueous solution with two different salinities, with the aid of interfacial tension (IFT) measurement, zeta potential, and dynamic light scattering (DLS) analysis. In addition, the most important parameters that can affect the IFT of crude oil/surfactant solutions (i.e. charge of the hydrophilic group and chain length of the hydrophobic hydrocarbon group of the surfactants and different characteristics of crude oil such as °API, acidity, weight percentage of the asphaltene and resin fractions, their aromaticity and polarity, and asphaltene stability parameter) were comprehensively analyzed. The results showed that IFT values, surface charge of the aggregates, and the size of microemulsions depend on the crude oil type, ionic strength, and type of surfactants, however, without any straightforward proportionality with the examined parameters. Among the considered surfactants, the cationic and non-ionic surfactant showed the lowest and highest dependency to the crude oil type, respectively. A paramount efficiency was obtained for CTAB cationic surfactant with the microemulsion size of 102 nm and surface charge at near isoelectric point (zeta potential of 3.5 mV).

Solubilization of Aldehydes and Amines in Aqueous CiEj Surfactant Aggregates: Solubilization Capacity and Aggregate Properties.

Hydroformylation of olefins to aldehydes and subsequent reductive amination of aldehydes to amines takes place in an aqueous system using a water-soluble catalyst. It is limited to short-chain molecules due to an insufficient solubility of long-chain molecules in water. A promising approach to increase the solubility of long-chain aldehydes and amines is the addition of surfactants to the aqueous phase. In this work, we thus determined the solubilization capacity (SC) of different nonionic CiEj surfactants (C8E6, C10E6, and C10E8) toward long-chain aldehydes and amines. We used static and dynamic light scattering techniques to investigate the influence of both the surfactant and solute molecular structures on the SC as well as on the aggregation number (Nagg) and hydrodynamic radius (Rh) of mixed aggregates. Our data reveals that an optimum ratio of hydrophobic to hydrophilic chain length of CiEj surfactants exists where the SC toward long-chain aldehydes and amines possesses a maximum. Further, the size of the aggregates (Nagg, Rh) passes through a minimum upon amine solubilization, while upon aldehyde solubilization, the aggregate size increases gradually. The results shown in this work give valuable insights to the solubilization of aldehydes and n-amines into nonionic CiEj surfactants and facilitate the search of suitable surfactants for hydroformylation and reductive amination as "green" solvents based on the detailed knowledge about the aggregate structure.

Construction of Enzyme-Responsive Micelles Based on Theranostic Zwitterionic Conjugated Bottlebrush Copolymers with Brush-on-Brush Architecture for Cell Imaging and Anticancer Drug Delivery.

Bottlebrush copolymers with different chemical structures and compositions as well as diverse architectures represent an important kind of material for various applications, such as biomedical devices. To our knowledge, zwitterionic conjugated bottlebrush copolymers integrating fluorescence imaging and tumor microenvironment-specific responsiveness for efficient intracellular drug release have been rarely reported, likely because of the lack of an efficient synthetic approach. For this purpose, in this study, we reported the successful preparation of well-defined theranostic zwitterionic bottlebrush copolymers with unique brush-on-brush architecture. Specifically, the bottlebrush copolymers were composed of a fluorescent backbone of polyfluorene derivate (PFONPN) possessing the fluorescence resonance energy transfer with doxorubicin (DOX), primary brushes of poly(2-hydroxyethyl methacrylate) (PHEMA), and secondary graft brushes of an enzyme-degradable polytyrosine (PTyr) block as well as a zwitterionic poly(oligo (ethylene glycol) monomethyl ether methacrylate-co-sulfobetaine methacrylate) (P(OEGMA-co-SBMA)) chain with super hydrophilicity and highly antifouling ability via elegant integration of Suzuki coupling, NCA ROP and ATRP techniques. Notably, the resulting bottlebrush copolymer, PFONPN9-g-(PHEMA15-g-(PTyr16-b-P(OEGMA6-co-SBMA6)2)) (P2) with a lower MW ratio of the hydrophobic side chains of PTyr and hydrophilic side chains of P(OEGMA-co-SBMA) could self-assemble into stabilized unimolecular micelles in an aqueous phase. The resulting unimolecular micelles showed a fluorescence quantum yield of 3.9% that is mainly affected by the pendant phenol groups of PTyr side chains and a drug-loading content (DLC) of approximately 15.4% and entrapment efficiency (EE) of 90.6% for DOX, higher than the other micelle analogs, because of the efficient supramolecular interactions of π–π stacking between the PTyr blocks and drug molecules, as well as the moderate hydrophilic chain length. The fluorescence of the PFONPN backbone enables fluorescence resonance energy transfer (FRET) with DOX and visualization of intracellular trafficking of the theranostic micelles. Most importantly, the drug-loaded micelles showed accelerated drug release in the presence of proteinase K because of the enzyme-triggered degradation of PTyr blocks and subsequent deshielding of P(OEGMA-co-SBMA) corona for micelle destruction. Taken together, we developed an efficient approach for the synthesis of enzyme-responsive theranostic zwitterionic conjugated bottlebrush copolymers with a brush-on-brush architecture, and the resulting theranostic micelles with high DLC and tumor microenvironment-specific responsiveness represent a novel nanoplatform for simultaneous cell image and drug delivery.

Influence of Temperature and Concentration on the Self-Assembly of Nonionic CiEj Surfactants: A Light Scattering Study

Nonionic poly(ethylene oxide) alkyl ether (CiEj) surfactants self-assemble into aggregates of various sizes and shapes above their critical micelle concentration (CMC). Knowledge on solution attributes such as CMC as well as aggregate characteristics is crucial to choose the appropriate surfactant for a given application, e.g., as a micellar solvent system. In this work, we used static and dynamic light scattering to measure the CMC, aggregation number (Nagg), and hydrodynamic radius (Rh) of four different CiEj surfactants (C8E5, C8E6, C10E6, and C10E8). We examined the influence of temperature, concentration, and molecular structure on the self-assembly in the vicinity of the CMC. A minimum in the CMC vs temperature curve was identified for all surfactants investigated. Further, extending the hydrophilic and hydrophobic chain lengths leads to an increase and decrease of the CMC, respectively. The size of the aggregates strongly depends on temperature. Nagg and Rh increase with increasing temperature for all surfactants investigated. Additionally, Nagg and Rh both increase with increasing surfactant concentration. The data obtained in this work further improve the understanding of the influence of temperature and molecular structure on the self-assembly of CiEj surfactants and will further foster their use in micellar solvent systems.

Self‐assembly of gemini amphiphiles with symmetric tails in selective solvent

AbstractGemini amphiphile is a special type of block copolymers formed by connecting two traditional diblock molecules at hydrophilic head groups through spacers. The special structure makes gemini amphiphiles potentially promising for drug delivery and gene delivery. The self‐assembly behavior of gemini amphiphiles with tails of equal length in selective solvent was investigated using the dissipative particle dynamics method. The effects of the size of the hydrophilic head group, interaction parameters, concentration and hydrophobic tail chain length on the self‐assembled morphology of gemini amphiphiles were examined. By varying these parameters, worm‐like micelles, large compound micelles, vesicles, hierarchical rod‐like micelles, cylindrical bundles, pomegranate‐like micelles and bilayers were obtained. Compared with conventional diblock copolymers, the dominant feature of gemini amphiphiles is the presence of the spacer. By analyzing the distance between two head groups, we explored in depth the influence of spacer length on the self‐assembly of gemini amphiphile molecules. Through simulation probes, we hope to improve the understanding of ordered aggregates of gemini amphiphiles in selective solvent, to reveal theoretically the pattern variation of aggregation morphology and to provide guidance for their practical application. © 2022 Society of Industrial Chemistry.

Molecular interaction between sodium dodecylbenzene sulfonate and octylphenol polyoxyethylene ether and effect of hydrophilic chain

The micellization behavior of two binary mixtures of an anionic sodium dodecylbenzene sulfonate with a nonionic surfactant octylphenol polyethoxylated ether (including OP-10 or OP-7) was investigated in aqueous solution at 298.15 K using the tensiometry, and the effect of hydrophilic chain of nonionic surfactant was discussed. In the framework of pseudophase separation model and based on the regular solution theory, the related micellization parameters and thermodynamic parameters were estimated by some models including Clint’s model, Rubingh’s model, etc. The two mixtures exist some differences in the micellization behavior. The synergistic effect, the antagonism, nonideal mixing and ideal mixing are observed in the two mixtures. The dependence of the mixed critical micelle concentration, the composition in mixed micelle, the interaction parameter between molecules on the composition in aqueous solution is explained by the electrostatic interaction, the steric effect and the shell structure of mixed micelle, etc. Thermodynamic parameters are adopted to account for the difference in energy and verify the micellization behavior. The two binary mixtures show different contributions of energy to the process of micellization. These findings help with understanding the nature on the interaction between two surfactants and the effect of the length of hydrophilic chain of nonionic surfactant so as to obtain some information in theoretical and practical investigations.

Effect of surfactant lengths on gas-liquid oxygen mass transfer from a single rising bubble

This work is an experimental investigation of the effect of the nature of surfactants on oxygen mass transfer. The study focuses on three cationic surfactants with different hydrophobic chain lengths, and four nonionic surfactants with different hydrophilic chain lengths. Equilibrium adsorption isotherms are calculated for each surfactant from experimental values of surface tension in static conditions. Surfactant solutions at concentrations between 2.5 × 10-8 and 5 × 10-3 mol/L were prepared and oxygen transfer from millimetric air bubbles (between 0.82 and 1.08 mm) was measured by Planar Laser Induced Fluorescence with Inhibition (PLIF-I). When the bulk concentration of surfactant was increased, results showed a sharp decrease of bubble velocity, in the range of 283–75 mm/s, and of liquid-side mass transfer coefficient, in the range of 5.6 × 10-4–0.4 × 10-4 m/s. This effect was observed for all surfactants studied. However, the length of the hydrophilic chain did not appear to affect the hydrodynamics of the rising bubble or the oxygen transfer at the same bulk concentration. Furthermore, for the same bulk concentration, increasing the hydrophobic chain length had an impact on the velocity and the mass transfer coefficient of oxygen. Finally, the Sherwood number was calculated in each medium and compared with classical correlations for gas–liquid mass transfer prediction. Those correlations seemed to reach a limit for a very concentrated medium.

Controlling impact behavior on superhydrophobic surfaces for droplets of nonionic surfactants by tailoring hydrophilic chain length

The behavior of high-speed droplets impacting on superhydrophobic surfaces plays an essential role in many daily applications. Adding surfactants is one excellent approach to improve droplet retention through enhancing the solid-liquid interface interaction. However, the regulating of the impact process has been rarely concerned about the effect of molecular structure on it. In our work, we study the impact behavior of nonionic surfactants Triton X (TX) on superhydrophobic surfaces by characterizing the diffusion rate of surfactant molecules and the receding contact angle and adhesion of surfactant solution on surfaces. We reveal that droplets of TX surfactant solution can deposit better on superhydrophobic surfaces as hydrophilic (ethylene oxide, EO) chain length increasing, which is mainly attributed by the faster diffusion speed towards the newly formed interface during the spreading phase, leading to better wettability transition and larger pinning area on the substrate. Our work promotes the understanding of the mechanism that controls the impact behavior of droplets of surfactant by adjusting the EO chain length, which provides an effective strategy to control droplet deposition on superhydrophobic surfaces.