Critical Micelle Concentration Values Research Articles

Effects of ionic liquid on micellar aggregate formed by pluronic (F-127) and non-ionic surfactant (TX-100) in aqueous solution

Although ionic liquids have a great deal of application, a few of the most popular ones are in separations, battery electrolyte development, and electrocatalysis. The synergistic interaction between surface-active ionic liquid (1-hexadecyl-3-methylimidazolium chloride, SAIL) and pluronic (F-127)/non-ionic surfactant (TX-100) has been investigated at 298.15 K. The examined mixture's critical micelle concentration (cmc) values for various compositions are significantly lower than those of pure amphiphiles (due to the strong attractive interaction between components). In this study, the surface tension method was used to calculate the cmc values of single and mixed amphiphiles. The mole fractions of the components in the mixed micelle as well as the mixed monolayer and interaction parameter were specified by regular solution theory (RST) using the data from experimental observations. Several thermodynamic parameters were also calculated for the mixed micellization of SAIL with F-127/TX-100. In the current mixed systems, the data obtained show that the ΔGM and ΔGIdealM are negative while ΔSM is positive, implying a spontaneous process of micellization. Using Maeda's theory, it was found that the stability of mixed micelles in these systems depended profoundly on chain-chain interactions. UV-visible spectroscopy further supports the positive interaction between SAIL and nonionic surfactants. The SAIL absorption spectra demonstrate an increase in absorption with increasing surfactant concentrations without any shift, supporting the creation of a new complex. The F-127+SAIL mixture has a higher binding constant value, indicating that SAIL interacts with pluronic more effectively.

Can sodium 1-alkylsulfonates participate in the sodium dodecyl sulfate micelle formation?

The aggregation behavior of sodium dodecyl sulfate (SDS) was studied in an aqueous solution in the presence of increasing concentrations of selected sodium 1-alkylsulfonates, namely sodium 1-octanesulfonate, sodium 1-decanesulfonate, and sodium 1-dodecanesufonate. The critical micelle concentration (CMC) of SDS was determined by conductivity and fluorescence intensity measurements. The steady-state fluorescence quenching experiments with pyrene as a fluorescent probe were performed to obtain micellar aggregation numbers (Nagg) of the surfactant. The thermodynamic parameters of micellization (ΔGmic0 for all studied systems; ΔHmic0 and ΔSmic0 for sodium 1-dodecanesufonate) have been determined and compared. The influence of alkyl chain length and concentration of the selected sodium 1-alkylsulfonates on the values of CMC, Nagg, ΔGmic0, ΔHmic0, and ΔSmic0 of SDS has been discussed. As it was found, all selected for the experiments electrolytes decrease significantly the CMC of the surfactant, while an opposite effect is observed for Nagg values. The obtained experimental results have been supported by theoretical calculations. Interestingly, it has been proven that solely the molecules of sodium 1-dodecanesufonate (of the same carbon chain length) may act as the SDS mimetics – they are not recognized by SDS as the ones with a different structure and consequently are allowed to participate in the formation of the surfactant’s micelles.

Tethered Bilayer Lipid Membrane Platform for Screening Triton X-100 Detergent Replacements by Electrochemical Impedance Spectroscopy.

In light of regulatory considerations, there are ongoing efforts to identify Triton X-100 (TX-100) detergent alternatives for use in the biological manufacturing industry to mitigate membrane-enveloped pathogen contamination. Until now, the efficacy of antimicrobial detergent candidates to replace TX-100 has been tested regarding pathogen inhibition in endpoint biological assays or probing lipid membrane disruption in real-time biophysical testing platforms. The latter approach has proven especially useful to test compound potency and mechanism of action, however, existing analytical approaches have been limited to studying indirect effects of lipid membrane disruption such as membrane morphological changes. A direct readout of lipid membrane disruption by TX-100 detergent alternatives would be more practical to obtain biologically relevant information to guide compound discovery and optimization. Herein, we report the use of electrochemical impedance spectroscopy (EIS) to investigate how TX-100 and selected replacement candidates-Simulsol SL 11W (Simulsol) and cetyltrimethyl ammonium bromide (CTAB)-affect the ionic permeability of tethered bilayer lipid membrane (tBLM) platforms. The EIS results revealed that all three detergents exhibited dose-dependent effects mainly above their respective critical micelle concentration (CMC) values while displaying distinct membrane-disruptive behaviors. TX-100 caused irreversible membrane disruption leading to complete solubilization, whereas Simulsol caused reversible membrane disruption and CTAB induced irreversible, partial membrane defect formation. These findings establish that the EIS technique is useful for screening the membrane-disruptive behaviors of TX-100 detergent alternatives with multiplex formatting possibilities, rapid response, and quantitative readouts relevant to antimicrobial functions.

Effect of Amphotericin B on the thermodynamic stability, aggregation state, hemolysis and antifungal activity of Amphotericin B-nonionic surfactant micellar system

Amphotericin B (AmB) is a toxic and low solubility antifungal drug. In this paper, AmB was encapsulated by different nonionic surfactants and the effect of their structures on AmB was investigated. Three micellar systems were prepared: AmB/HS15, AmB/TW80, and AmB/ELP micellar systems. The interfacial and micellization behaviours of the three micellar systems were investigated. The critical micelle concentration (CMC) of different nonionic surfactant micelles was calculated and discussed independently. The results showed that the ELP molecules with three hydrophobic chains reduced the CMC value of the systems, contributing to the formation of drug-laden micelles. In addition, some interfacial and thermodynamic parameters were calculated and analyzed. On this basis, the particle size, aggregation number, transmittance, and in vitro release of each system were further determined, and the findings revealed that AmB/ELP micellar systems had more physical stability than AmB/TW80 and AmB/HS15 micellar systems, and all three micelle systems exhibited slow release properties. The AmB/ELP micellar system had a lower hemolytic toxicity than the AmB/TW80 and AmB/HS15 micellar systems in terms of hemolysis. The antifungal activity of the AmB/TW80 micellar system was reduced due to the large spatial resistance of the hydrophilic segment of the TW80 molecule, which prevented its binding with ergosterol, making the antifungal activity of the AmB/TW80 micellar system much lower than that of the AmB/ELP and AmB/HS15 micellar systems. In summary, different nonionic surfactant structures have a significant impact on the toxicology and pharmacology of AMB, which provides new research ideas for the development of new dosage forms.

Interaction and physicochemical parameters of dodecyltrimethylammonium bromide and crystal violet dye mixture in aqueous alcohols and urea solution: Effects of change in composition and temperature

Herein, the interaction between dodecyltrimethylammonium bromide (DTAB), a cationic surfactant, and crystal violet (CV) has been studied by applying the conductometric method in aqueous solutions of short chain alcohols (ethanol, 1-propanol) and urea. The critical micelle concentration (CMC), counter ion binding (β) and the thermodynamics parameters (ΔGm0, ΔSm0 and ΔHm0) for the assembly of DTAB + CV system were determined. For the DTAB + CV micellization in presence of aqueous alcohols and urea solutions, a single break point was obtained in every circumstance. The values of CMC for the study system are found to upsurge with the increase of concentration of alcohols and urea as well as with the increase of temperature. The ΔGm0 values were found negative for DTAB + CV mixtures in the study media, which indicated that the micellization process was thermodynamically spontaneous. In all cases, the -ΔHm0 and -ΔSm0 values disclosed that the recommended interaction forces functioning amid DTAB and CV are the hydrophobic and electrostatic interactions.

Influence of twin-headed gemini micellar system on the study of methionine amino acid with ninhydrin in buffer solution.

The influence of double-headed gemini was examined in the present study by studying the amino acid methionine mixed with ninhydrin in CH3COOH-CH3COONa buffer solvent. The absorbance was monitored at fixed time intervals with UV-vis spectroscopy. An impact typical of surfactants was observed on the ninhydrin-methionine reaction and explained by a pseudo-phase model of micelles. The effect of different temperatures (343 to 363 K) was also determined. Based on data showing the impact of temperature on kψ , several relevant thermodynamic quantities, ΔH #, ΔS #, and E a, were calculated using linear least-squares regression. In addition, the influence of the other reaction ingredients on the reaction, that is, pH and the concentration of ninhydrin and methionine, was studied. The CMC (critical micelle concentration) of pure geminis and the surfactant system with methionine and ninhydrin was evaluated at two temperatures, i.e. at 303 K and 353 K by conductivity measurements. The CMC values of pure gemini surfactants evaluated in the existing case at 303 K are concordant with the results stated before. Moreover, other parameters, including rates and binding constants, were calculated.

Antibacterial and antibiofilm potential of Lacticaseibacillus rhamnosus YT and its cell-surface extract

BackgroundFoodborne pathogens and spoilage bacteria survived in the biofilm pose a serious threat to food safety and human health. It is urgent to find safe and effective methods to control the planktonic bacteria as well as the biofilm formation. Substances with antibacterial and antibiofilm activity found in lactic acid bacteria were mainly metabolites secreted in the cell-free supernatant. Previously, Lacticaseibacillus rhamnosus YT was isolated because its cell pellets displayed distinguished antibacterial activity under neutral conditions. This study aimed to investigate the antibacterial and antibiofilm properties of the L. rhamnosus YT cells and its crude cell-surface extract.ResultsThe antibacterial activity of the L. rhamnosus YT cells constantly increased with cells growth and reached the peak value after the cells grew into stationary phase. After cocultivation with the L. rhamnosus YT cells, the biofilm formation of B. subtilis and S. enterica was reduced. The antibacterial activity of the L. rhamnosus YT cells was varied along with various culture conditions (carbon sources, nitrogen sources, medium pH and cultural temperatures) and the antibacterial intensity (antibacterial activity per cell) was disproportional to the biomass. Furthermore, the cell-surface extract was isolated and displayed broad antimicrobial spectrum with a bacteriostatic mode of action. The antibiofilm activity of the extract was concentration-dependent. In addition, the extract was stable to physicochemical treatments (heat, pH and protease). The extract performed favorable emulsifying property which could reduce the water surface tension from 72.708 mN/m to 51.011 mN/m and the critical micelle concentration (CMC) value was 6.88 mg/mL. Besides, the extract was also able to emulsify hydrocarbon substrates with the emulsification, index (E24) ranged from 38.55% (for n-hexane) to 53.78% (for xylene). The E24 for xylene/extract emulsion was merely decreased by 5.77% after standing for 120 h. The main components of the extract were polysaccharide (684.63 μg/mL) and protein (120.79 μg/mL).ConclusionThe properties of the extract indicated that it might be a kind of biosurfactant. These data suggested that L. rhamnosus YT and the cell-surface extract could be used as an alternative antimicrobial and antibiofilm agent against foodborne pathogens and spoilage bacteria in food industry.

Interaction and micellar behavior of ternary mixture of amphoteric amino sulfonate surfactant with traditional anionic and nonionic surfactants: Effect of hydrophilicity

The micellization and the molecular interaction behaviors for two ternary mixtures constituted by an amphoteric sodium 3-(n-dodecyl ethylenediamino)-2-hydroxypropyl sulfonate (C12AS), an anionic sodium dodecylbenzene sulfonate (SDBS) and a nonionic octylphenol polyoxyethylated ether with the number (n) of oxyethylene glycol ethers OP-n (n = 10 or 7) in aqueous solution were investigated using the tensiometry and the effect of hydrophilicity on them was also discussed. In the framework of pseudophase separation model and based on the regular solution theory, the related micellization parameters including the mixed critical micelle concentration (cmc) values in the ideal and real cases, the activity coefficients and the compositions in mixed micelle, etc. and thermodynamic parameters were estimated by the Clint’s model and the Rubingh’ model. The mixed cmc value is dependent on the composition in aqueous solution and influenced by the hydrophilicity of nonionic surfactant. With increasing the nonionic in ternary mixture, the mixed cmc value is initially decreased and then slightly rise. An increasing in the hydrophilicity of nonionic will make the minimum value of mixed cmc be increased from 1.299 mM to 1.705 mM. The resulting phenomena can be explained reasonably by the electrostatic effect, the steric hindrance, the hydrogen bonding, etc. Thermodynamic data indicate that the contribution of entropy or enthalpy plays a vital role on the spontaneous process of micellization and the share of entropy or enthalpy in free energy change is dependent largely on the amount of nonionic surfactant and the hydrophilicity. In ternary mixtures of C12AS/SDBS/OP-10, an increase in an amount of OP-10 will induce the change from the enthalpy-driven micellization process to the entropically favorable process. Once an abundant amount of OP-7 is added, while, the enthalpy will make a main contribution on the micellization process, which can be described by the drop in the share of entropy at the composition (0.6970/0.0000/0.3030) of ternary mixture from 0.6478 to 0.4901. These findings will help with understanding the molecular interaction behavior for the ternary surfactant mixture and the effect of the addition of nonionic surfactant and its hydrophilicity.

Preparation of reversible cross-linked amphiphilic polymeric micelles with pH-responsive behavior for smart drug delivery.

A new type of reversible cross-linked and pH-responsive polymeric micelle (PM), poly[polyethylene glycol methacrylate-co-2-(acetoacetoxy)ethyl methacrylate]-b-poly [2-(dimethylamino)ethyl methacrylate] [P(PEGMA-co-AEMA)-b-PDMAEMA], was synthesized for targeted delivery of curcumin. After reversible cross-linking of the micellar shell, the PMs with a typical core-shell structure exhibited excellent stability against extensive dilution and good reversibility of pH-responsiveness in solutions with different pH values. P(PEGMA9-co-AEMA6)-b-PDMAEMA10 has the lowest critical micelle concentration (CMC) value (0.0041 mg mL-1), the highest loading capacity (13.86%) and entrapment efficiency (97.03%). A slow sustained drug release at pH 7.4 with 12.36% in 108 h, while a fast release (42.36%) was observed at pH 5.0. Furthermore, a dissipative particle dynamics (DPD) simulation method was employed to investigate the self-assembly process and pH-responsive behavior of PMs. The optimal drug-carrier ratio (2%) and fraction of water (92%) were confirmed by analyzing the drug distribution and morphology of micelles during the self-assembly process of the block copolymer. The simulation results were consistent with experimental results, indicating DPD simulation shows potential to study the structure properties of reversible cross-linked micelles. The present findings provide a new method for the development of SDDS with good structural stability and controlled drug release properties.

An electrolyte induced thermodynamic study of quercetin and Tween 20: A physico-chemical approach for formulation development

The present study represents the thermodynamic interactions between the non-ionic surfactant Tween 20 and the well-known flavonoid quercetin. The conductivity experiments were conducted at five different temperatures (20 °C, 25 °C, 30 °C, 35 °C and 40 °C) using various quercetin concentrations (1 mM, 2 mM and 3 mM) in 70 % v/v ethanol as a solvent. To overcome the non-conducting behavior of non-ionic surfactant Tween 20, as an electrolyte, sodium chloride solution (1 % w/v) was added. The critical micelle concentration (CMC) and XCMC values were calculated as a function of temperature using the specific conductivity experiments. In addition, a number of thermodynamic parameters, including change in Gibbs free energy of micellization (ΔGom), change in enthalpy (ΔHom), and entropy (ΔSom), have been estimated. Overall, the effects of quercetin on Tween 20′s micellization behaviour have been studied.

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

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

Tensiometric and Fluorescence Study of Cationic Gemini Surfactant with Some Special Alcohols

Special alcohols have been used as additives to study interfacial properties of cationic Gemini surfactant pentanediyl- 1, 5-bis (dimethyldodecylammonium bromide) (12-5-12). As these branched chain alcohols (in comparison with linear chain alcohols) are playing a measure roll in creating a microemulsion with Gemini surfactants. The surface tension values were measured by using ring detachment method. During the experiments, the ring was cleaned well by heating it in alcohol flame. The critical micelle concentration (cmc) values were obtained from surface tension (γ) versus logCt plots. The γ values decreased continuously and then become constant along a wide concentration range. The point of break, when the constancy of surface tension begins, was taken as the cmc of the system. Calculated Parameters are cmc, Гmax (maximum surface excess concentration), Amin (minimum surface area per molecule), C20 (the concentration of surfactant where the surface tension of the solvent is being reduced by 20 mN.m-1), (free energy of the given air/water interface), and the standard Gibbs energy of adsorption, ΔG­­0ads. An important property of micelle formation is the mean aggregation number which provides direct information about the general size and shape of the aggregates formed by amphiphiles in solution, and how these properties are related to the molecular structure of the amphiphiles. Mixed micellization behavior has been shown by these parameters. The mean aggregation number (Nagg­) of mixed micelles has been obtained by using the steady state fluorescence quenching method. Some other concerned parameters including dielectric constant (D), binding constant (KSV) were calculated in this study by using the ratio of intensity of peaks.

Synthesis and anti-bacterial/fungal activities of amphiphilic polysiloxanes primary ammonium salts

Amphiphilic cationic polymers are currently used as antimicrobial agents to disrupt microbial membranes with long-termed stability and low bio-toxicity. However, there are few studies on the relationship between molecular structure and antimicrobial properties of amphiphilic polymers containing primary amine salts against fungi. In this work, a series of polysiloxanes graft primary ammonium salts (PDMS-g-AH) with tunable molecular weights (3 kDa, 5 kDa, 8 kDa, and 10 kDa) and grafting ratios (50% and 75%) were synthesized via thiol-ene “click reaction”, and the effect of their structural parameters on the broad-spectrum inhibition of bacteria (Escherichia coli and Staphylococcus albus) and pathogenic fungi (Candida albicans), especially on two phytopathogenic fungi (Fusarium oxysporum f. sp. cubense race 4 (Foc4) and Rhizoctonia solani (R. solani)) were systematically assessed. The aggregation of polymers in water was characterized by the critical micelle concentration (CMC) values, zeta potentials, and particle sizes and distributions. All PDMS-g-AH had positive zeta-potential values and exhibited high micellar stability in water. At the same time, the aggregation characteristics of polymers are affected by the structure and molecular weight of polymers. Small aggregates and high zeta-potentials interacted easily with the microbial cell membranes, which affected the antimicrobial activity together. These results indicated that the block type of PDMS-g-AH, i.e., PDMS-b-AH, showed better antimicrobial activities than the random type (PDMS-co-AH), and the optimal antimicrobial activities were obtained for moderate polymer chain length (about 5 kDa). This work reveals the relationship between the chemical structure of PDMS-g-AH, their aggregation behavior in water as well as interaction with biological membranes during the sterilization process, which provides the potential applications as fungicidal agents for effectively controlling plant diseases, such as rice sheath blight and banana Fusarium wilt.

Mixed micelle formation by sodium dodecylsulfate and dodecyltrimethylammonium bromide in aqueous ionic liquid media

Surfactant self-aggregation within ionic liquid (IL) - based media has been investigated to compare and contrast the role of such media with that of water. Behavior of a surfactant mixture constituting of two surfactants with oppositely charged head groups, namely anionic sodium dodecylsulfate (SDS) and cationic n-dodecyltrimethylammonium bromide (DTAB), is assessed in aqueous IL media. Contrary to what is observed in water, it is shown earlier that effective charge screening of the surfactant headgroups by IL ions in a typical IL 1-ethyl-3-methylimidazolium ethylsulfate ([C2C1im][EtSO4]) results in formation of (SDS + DTAB) mixed micelles with critical micelle concentrations (CMCs) ranging between those of SDS and DTAB, respectively. The miscibility of (SDS + DTAB) mixture in aqueous [C2C1im][EtSO4] reveals that as the content of IL [C2C1im][EtSO4] is increased, the miscibility of the surfactant mixture improves indicating increased charge screening involving ions of the IL and the surfactant headgroups. For water mole fraction (XW) ≤ 0.90, (SDS + DTAB) surfactant mixture is miscible in aqueous [C2C1im][EtSO4] system in all proportions. For 1.00 ≥ XW≥ 0.90, while synergism persists due to the presence of attractive electrostatic attraction between SDS and DTAB headgroups leading to mixture CMCs below the CMCs of SDS and DTAB, respectively, the extent of synergism diminishes with increase in IL [C2C1im][EtSO4] in the solution. For XW = 0.80, the (SDS + DTAB) mixture exhibits CMC values that are closest to the values estimated assuming ideal behavior. For 0.70 ≥ XW ≥ 0.30, the (SDS + DTAB) exhibits antagonistic trend with CMC values higher than those estimated for ideal solution; the antagonistic trend gradually decreases with increase in [C2C1im][EtSO4] and again attains close to ideal behavior in neat IL [C2C1im][EtSO4]. This trend is subsequently manifested in the composition of the mixed micelles as well as in the net interaction parameter, β. Addition of small proportion of IL to water helps in solubilization of surfactant mixture of oppositely charged surfactants due to effective charge screening of the surfactant headgroups and results in formation of mixed micelles in aqueous IL media over complete composition range.

Green Synthesis, Surface Activity, Micellar Aggregation, and Foam Properties of Amide Quaternary Ammonium Surfactants.

A series of amide quaternary ammonium surfactants with the formula C n H2n+1CONH(CH2)2N+(CH3)3·CH3CO3 - (n = 9, 11, 13, 15) were synthesized using a fatty acid, N,N-dimethylethylenediamine, and a green reagent dimethyl carbonate. A comparative study of the four surfactants in terms of surface activity, aggregation characteristics, and foam properties was conducted. The results show that these amide quaternary ammonium surfactants reduce the surface tension of water to a minimum value of 23.69 mN·m-1 at a concentration of 1.55 × 10-4 mol·L-1 and self-assemble spontaneously into aggregates, which are mostly vesicles. Furthermore, with increasing the alkyl chain length, their critical micelle concentration (CMC) values and surface tension values at the CMC (γCMC) decrease and then increase, and the degree of counterion binding (β) decreases. It is also found that these amide quaternary ammonium surfactants exhibit excellent foam ability and foam stability.

Red beet plant as a novel source of natural surfactant combined with ‘Smart Water’ for EOR purposes in carbonate reservoirs

The use of natural green surfactants has become one of the most popular techniques for enhanced oil recovery (EOR) because these types of surfactants are environmentally-friendly, efficient, sustainable, and less expensive than commercial surfactants. In the current study, the extraction of natural surfactant from the Red Beet (RB) plant is introduced for EOR applications in carbonate reservoirs. Characterization analyses using TGA, FT-IR, 1H NMR, and FESEM were carried out to assess the nature of the extracted saponin as the surfactant agent. The physicochemical characterization points to a nonionic surfactant. The role of salinity, with varying NaCl concentrations, in ‘smart water’ flooding using the RB surfactant was then investigated. According to the measured interfacial tension (IFT), the critical micelle concentration (CMC) of the extracted surfactant from the RB plant was 2500 ppm, and the IFT value at the CMC point was 9.92mN/m for deionized water. The parametric flooding study revealed that the RB surfactant injection as the source of the green surfactant (at its CMC value with 15,000 ppm NaCl as the optimum salinity) contributed, as the tertiary recovery, to an extra 26.29 % of the original oil in place (OOIP) because of a considerable decrease in contact angle from 151.4° to 42.14° and a decline in IFT values from 33.87 to 9.27 mN/m.

Investigation of an anaesthetic drug (tetracaine hydrochloride) in the presence of ionic fluid and surfactant: Mixed micellization & spectroscopic studies

The effect of ionic liquid and cationic surfactant on the physicochemical characteristic of an anaesthetic drug (tetracaine hydrochloride, TCH) has been studied in the current task. The ionic fluid (1-hexadecyl-3-methyl imidazolium chloride, SAIL) and cationic surfactant (cetylpyridinium chloride, CPC) used in this study are of the same hydrophobic chain length. Tensiometric and absorption spectroscopic methods have been castoff to study the interaction of TCH with SAIL/CPC. The critical micelle concentration (cmc) values of single and mixed amphiphiles were computed by the surface tension method. In addition to cmc, maximum surface excess concentrations (Γmax), minimum surface areas per surfactant molecule (Amin), surface tension at the cmc (γcmc), surface tension reduction efficiency (πcmc), and several thermodynamic parameters of mixed micellization were measured. The calculated average value for the interaction parameter (βRub) suggests TCH show higher synergistic interaction with SAIL compared to CPC. The better attractive interaction (synergism) between SAIL and TCH is also confirmed by UV–visible spectroscopy. The absorption spectra of the drug show increase in the absorption with increasing the concentration of surfactants without any shift confirming the formation of a new complex. The binding constant value is more for the TCH + SAIL mixture.

Cationic Surfactants Based on Arginine-Phenylalanine and Arginine-Tryptophan: Synthesis, Aggregation Behavior, Antimicrobial Activity, and Biodegradation.

Cationic surfactants have great potential as drug vehicles and for use in gene therapy (cationic vesicles made from cationic surfactants can encapsulate RNA or DNA for cellular transfer). They can also be used as antimicrobial and antifungal agents to treat human infections. In an era of increasing antimicrobial resistance, the development of new biocompatible surfactants suitable for application as antimicrobial agents is of high interest. In this work, a library of amino acid-based surfactants was synthesized, characterized and tested for antimicrobial activity. The head group architecture (number and type of amino acids, density of cationic charge, ionic character) and the hydrophobic moiety (alkyl chain length and position of the hydrophobic group) were systematically modified, and the effect on the surfactant biological and aggregation behavior was studied. Thus, the pKa values, micellization process, antimicrobial efficiency and biodegradability were evaluated. The critical micelle concentration values of the surfactants depended on their hydrophobic character, but changes in the polar head as well as the position and length of the alkyl chain also significantly affected activity against some of the tested microorganisms. Moreover, biodegradability was closely related to the hydrophobic character of the surfactant and attachment of the alkyl chain to the polar head. The structure-activity relationships established here may open perspectives for the design of effective biodegradable antimicrobial materials that can overcome emerging resistance.

Thermodynamic and Spectroscopic Studies of SDS in Cinnamaldehyde + Ethanol Mixtures: Influences of Temperature and Composition

The study of intermolecular interactions between ethanol (E-OH), cinnamaldehyde (CAD) with anionic surfactant sodium dodecyl sulfate (SDS) in non-aqueous media has been examined by utilizing conductometric and spectroscopic techniques. The critical micelle concentration (CMC) values have been determined. The experimental conductance data were analyzed against temperature and concentration using standard relations. The pseudo phase separation model has been adopted to calculate various thermodynamic parameters like standard free energy, ∆G°mic, enthalpy, ∆H°mic, and entropy, ∆S°mic, of micelle formation. Fourier transforms infrared analysis (FTIR), and Fluorescence spectra were taken out to assess the possible interactions prevailing in the micellar systems. The findings demonstrated that the presence of SDS, and the composition of CAD + ethanol might affect the thermodynamic parameters. The discrepancy in these parameters with the surfactant concentration or with the temperature change indicates the manifestation of different interactions prevailing in the studied systems.

Experimental Study of the Influence of Inorganic Salts on Foam Stability

The aqueous film-forming foam (AFFF) extinguishing agent is suitable for fighting various hydrocarbon fuel fires due to its dual fire-fighting effect of foam and liquid film. Because the action law and microscopic mechanism of inorganic salts on the stabilization process of surfactant-generated AFFF are not perfect, this paper employs an experimental approach to investigate the effects of inorganic salt types and concentrations on sodium dodecyl sulfate-containing foam systems (SDS). Prior to critical micelle concentration (CMC), increasing inorganic salt concentration decreased solution surface tension, but the opposite was true after CMC. The CMC value of an SDS solution decreases as inorganic salt concentration increases, and the "salting effect" of inorganic salt cations also has an effect on the CMC value. Based on the resistance of the liquid film at the gas-liquid interface affecting gas transport, the foam evolution was divided into three stages: foam generation, liquid drainage, and gas transfer. The effect of inorganic salts on these three stages was studied at the molecular level, and it was discovered that the addition of NH4Cl and MgCl2 could improve the saturation adsorption at the gas-liquid interface, reduce the surface tension of the surfactant solution, and improve foam stability. Meanwhile, inorganic salts can change the force of gas molecules, so the equilibrium force of gas across the liquid membrane increases as inorganic salt concentration increases. Additionally, the addition of inorganic salts raises the diffusive drainage coefficient, but the gravity drainage coefficient still reigns supreme in the predecay period.