Free Energy Of Micellization Research Articles

Modulating the aggregation behavior of aqueous sodium dodecylsulphate (SDS) with addition of trisubstituted imidazolium based ionic liquid 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [bdmim][BF4

The aggregation behavior of an anionic surfactant sodium dodecylsulphate (SDS) in aqueous system in the presence of 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [bdmim][BF4], a trisubstituted ionic liquid (IL) has been studied. Critical micelle concentrations (cmcs) were determined from conductance measurements at a temperature range of 298.15–318.15K and using fluorescence probe at different wt% of IL. Results obtained from these methods are in good agreement with each other. An increase in cmc was observed for all the studied systems with increase in temperature as well as with increase in wt% of IL. Further the degree of dissociation, α and thermodynamic parameters viz. free energy of micellization, ΔGmo and entropy of micellization, ΔSmo has been evaluated. The aggregation number, Nagg of aqueous SDS micelles in the absence and presence of different wt% of [bdmim][BF4] is determined by fluorescence quenching of pyrene. 1H NMR measurements of post-micellar solutions have also been done to understand the different inter-molecular interactions of surfactant molecules in [bdmim][BF4].

Physicochemical investigation of novel biodegradable dicationic ester bonded m-E2-m gemini surfactants with bile salts: Insights from surface tension, dynamic light scattering and fluorescence

Due to the potential use of bile salts in drug delivery, the mixed micellar, microstrutural and mixed monolayer investigations of three biodegradable diester bearing cleavable gemini surfactants (m-E2-m; m=12, 14, 16) with sodium deoxycholate and sodium cholate in aqueous media have been carried out by tensiometry, dynamic light scattering and spectrofluorimetry studies. The micellar and adsorption characteristics like composition, mutual interaction, hydrodynamic radius, aggregation number, activity coefficient, minimum area per molecule, and free energies of micellization and adsorption have been evaluated and compared. A synergistic interaction was observed both in the micelle as well as at interface, as evident from interaction parameters. The results are discussed in terms of the structural characteristics and nature of spacer in the gemini surfactants as well as in terms of the presence of hydroxyl groups in bile salts. Furthermore, the m-E2-m geminis generate stronger synergistic interactions with sodium cholate as compared to sodium deoxycholate. Dynamic light scattering (DLS) and spectrofluorimetry results indicate microstructural evolution in the aqueous mixtures of m-E2-m geminis and bile salts which offer potential pharmaceutical applications.

Effects of Sodium Bromide Salt and Temperature on the behaviour of Aqueous Solution of Cetyltrimethylammonium Bromide

The effects of sodium bromide(NaBr) salt and temperature on the aggregation behaviour of cetyltrimethylammonium bromide (CTAB) have been studied using conductivity data.Conductivity was observed to vary increasingly with both temperature and salt concentration. The critical micelle concentration (CMC) of CTAB decreased with increase in the concentration of NaBr but increased as temperature increased. For example,the CMCs of CTAB in 0.0 and 10.0mM solutionsof NaBr at 30 °C were 1.68 and 1.50 mMrespectively while those of the same concentrations at 35 °C were 1.84 and 1.63respectively.It wasalso found that both salt and temperature influenced the degree of micelle ionization as well as the free energy of micellization. Results also showedthat the stability of CTAB micelles was enhanced by adding NaBr molecules.These observations have been discussedin terms of the electrostatic repulsion of charged CTAB head group.

Synthesis and Biological Activity of Some Amide-Based Cationic Surfactant complexes with Co (II) and Cu (II)

In this study, different cationic surfactants were prepared by esterfication of different fatty acids with ethanol then amidation of the prepared esters with N, N dimethyl ethylene diamine then quaternized the tertiary amines with benzyl bromide to produce a series of quaternary ammonium salts then preparing of metallocationic surfactants by complexing the cationic surfactants with cobalt chloride and copper chloride. Surface tension at different four temperatures of these metallocationic surfactants was investigated. The surface parameters including critical micelle concentration (CMC), maximum surface excess (Γmax), minimum surface area (Amin), efficiency (PC20) and effectiveness (πCMC) were studied and the thermodynamic parameters such as free energy of micellization (ΔG o mic) and adsorption (ΔG o ads), enthalpy (∆H o m), (∆H o ads) and entropy (∆S o m), (∆S o ads) were calculated. The antimicrobial activity of the prepared complexes was determined via the inhibition zone diameter against different microorganisms also the antimicrobial activity of the prepared complexes against sulfate reducing bacteria (SRB) was determined by the dilution method. The results indicate that these metallocationic surfactants have good surface properties and good biological

Computer Simulation of Micellization for Ring-like Block Copolymers

The micellization behaviour of ring-like AB diblock copolymers in a selective solvent was compared with the corresponding linear ABA triblock copolymers via Monte Carlo simulation. The simulation results show that the difference in the critical micellization concentration (cmc) values between ring-like copolymers and linear copolymers with same compositions is closely related to the content of A blocks, f(A), and the strength of attractive interaction between B monomers, epsilon. When fA is relatively small and e is big, the cmc values of ring-like block copolymers are smaller than those of the corresponding linear ones; whereas when fA is big and e is small, the cmc values of triblock copolymers are smaller than those of the corresponding ring-like ones. To further understand the effect of fA and e on the micellization behavior, we calculated the entropy and the potential energy contributions to the micellization free energy, respectively. The results show that in the studied range of fA and 8, the entropy loss in micellization for ring-like block copolymers is always smaller than that for triblock copolymers, so it seems that the micellization of ring-like block copolymers is always easier than that of the linear ones if we only consider the entropy contributions to the free energy. But if we calculate the potential energy contributions to the free energy, it can be found when fA is relatively small and 8 is big, the potential energy decreases greatly during the micellization of ring-like block copolymers. Considering the less unfavorable contribution of entropy part to the free energy for ring-like block copolymers, the micellization of ring-like block copolymers should be much easier than that of the linear ones. When f(A), is big and e is small, the potential energy decreases greatly when the micelles form for linear block copolymers. Although the entropic contribution to the free energy is unfavorable for linear ones, the potential energy still shows the dominative contribution to the free energy and therefore the micellization of linear block copolymers is much easier than the ring-like ones. The above analysis of the free energy will help us understand the micellization behavior of ring-like block copolymers and linear block copolymers.

Micellization Behavior of Butanediyl-1, 4-Bis(Dimethyldodecylammonium Bromide) Gemini Surfactant in Presence of Organic Additives

The surface and micellar properties of cationic gemini surfactant butanediyl-1, 4-bis(dimethyldodecylammonium bromide), referred to as C12-C 4 -C12, has been studied in pure aqueous solutions and in the presence of alcohols (butanol (C4OH), pentanol (C5OH), hexanol (C6OH)), and the corresponding amines (butylamine (C4NH2), pentylamine (C5NH2), hexylamine (C6NH2)) by surface tension measurements at 303 K. Parameters such as critical micelle concentration (CMC), C20 (the surfactant concentration required to reduce the surface tension of solvent by 20 mN m−1), the ratio of C20 and CMC, Γmax (maximum surface excess concentration at the air/solution interface), and Amin (minimum area per surfactant molecule) were evaluated. The CMC value of the gemini decreased with increasing concentration of additives. Mixed micelles were formed in each case and the CMC values of the mixtures were used to compute interaction parameters for mixed micelle formation in aqueous medium (βm), interaction parameters for mixed monolayer formation at the solution/air interface (βσ), and activity coefficients (f1 and f2). A synergistic interaction was observed both in the micelle as well as at the interface, as evident from the interaction parameters. Free energies of micellization () and adsorption () were also calculated.

Effective solubilization of chalcones in micellar phase: Conductivity and voltammetric study

The solubilization of four chalcones, between aqueous and micellar phases of ionic surfactants (SDS and CTAB), was investigated by conductivity and cyclic voltammetry (CV) techniques. From conductivity data, a decrease in the critical micellar concentration (CMC) of the surfactants, in presence of the chalcones was ascribed to the decreased charge density over the surfactants. The results were seconded by thermodynamic parameters including degree of ionization (α), counter ion binding (β), and standard Gibbs free energy of micellization (ΔGm○). The added surfactant decreased the peak current of the oxidized chalcone and shifted the peak potential either positively (in presence of SDS) or negatively (in presence of CTAB). The effect is rationalized as chalcone-surfactant interaction and quantitated as binding constant (Kb) assorting values from 8.78 to 552.97 M−1. The preferred solubilization of the chalcones in the micellar phase has been inferred.

Research of Surface Chemical Properties and Micellization Behavior of Sodium N-Lauroylglycine

Abstract Amphoteric surfactant, sodium N-lauroylglycine, was synthesized and symbolized as SLG. The surface chemical properties and micelle behaviors of SLG in 0–0.5 mol · L−1 aqueous solution of sodium chloride were investigated by surface tension measurements at 298–313 K. The critical micelle concentrations (cmc) of pure surfactant were determined in 0–0.5 mol · L−1 sodium chloride aqueous solution. Fluorescence and micelle aggregation number (N agg) measurements have been used to investigate the variations of micro-polarity and micellization behavior. The added NaCl has a tendency to increase the attractive interaction between the surfactant molecules in both the micellar phase and the adsorption layer. The Gibbs free energy of micellization (ΔG m 0 ) is negative for all investigated systems, and the thermodynamic parameters of SLG indicate that the micellization of SLG is entropy driven.

Thermodynamic and FTIR studies of the interactions between sodium dodecyl sulphate and strong acids – atypical conductivity pattern

Micellisation of sodium dodecyl sulphate (SDS) was studied in the presence of hydrochloric acid (HCl) and perchloric acid (HClO4) using conductometry method. The conductivity-[SDS] plots showed abnormal profile pattern at [HCl] > 0.002 mol dm−3 and [HClO4] > 0.001 mol dm−3. Below these acid concentrations, conductivity pattern was normal, and the critical micelle concentration (CMC) values of SDS were lower in both acids than in water. At high acid concentrations, post-micellar slopes were negative. Fourier transform infrared (FTIR) analysis showed significant shifts in the bands suggesting the formation of dodecyl hydrogen sulphate by SDS at high acid concentrations. Thermodynamic parameters for SDS micellisation at low acid concentrations ([HCl] = 0.002 mol dm−3 and [HClO4] = 0.001 mol dm−3) were determined in the temperature range 15–40°C. As temperature increases, the change in enthalpy and entropy of micellisation becomes less positive, and the change in free energy of micellisation becomes increasingly negative.

A study of the interaction between a phenothiazine drug promazine hydrochloride with cationic surfactants

A tensiometric study at 303.15K was made to study the binary mixed systems of a phenothiazine drug promazine hydrochloride with six cationic surfactants (decyl-, dodecyl-, tetradecyl-, hexadecyltrimethylammonium bromides, and cetylpyridinium bromide/chloride). Relevant parameters were evaluated by using the Regular Solution Theory and Motomura treatment for binary mixed systems. Clint's model was also used to explain the nonideal behavior of the systems. The synergistic behavior (i.e., non-ideal behavior) for binary mixtures is explained by the deviation of critical micelle concentration (cmc) from ideal critical micelle concentration (cmc*), micellar mole fraction (X1m) from ideal micellar mole fraction (X1ideal), the values of interaction parameter (β) and activity coefficients (fi) (for both mixed micelles and mixed monolayer). The excess free energy (ΔGex) explains the stability of mixed micelles in comparison to micelles of pure drug; the stability decreases with the increase in alkyl chain length of the surfactant. Interfacial parameters, i.e., Gibbs surface excess (Γmax), minimum head group area at air/water interface (Amin), free energy of micellization (ΔGmο), and standard Gibbs energy of adsorption (ΔGadsο) were also evaluated for the systems.

Micellization and interfacial behavior of 16-E2-16 in presence of inorganic and organic salt counterions

The effect of salts (inorganic and organic) was investigated and analyzed to probe the micellization behavior of a biodegradable ester-bonded cationic gemini surfactant ethane-1,2-diyl-bis(N,N-dimethyl-N-hexadecylammoniumacetoxy) dichloride, referred to as 16-E2-16. We investigated the critical micelle concentration (cmc), free energy of micellization (ΔG°m), free energy of adsorption (ΔG°ads) and aggregation number Nagg of the gemini surfactant with different types of salts (KCl, KNO3, KSCN, NaBen, and NaSal). Indeed, our results clearly indicate that the two kinds of counterions (obtained from the respective salts) affect the aggregation behavior of 16-E2-16 in quite different ways and the order of ability to promote surfactant aggregation is found to be as NaSal>NaBen>KSCN>KNO3>KCl. The counterions exert strong influence on the cmc, aggregation number and size and shape of aggregates of ionic surfactant systems. The results provide new insight in understanding the effect of ions on the delicate balance of forces controlling aggregate morphology and solution properties of charged amphiphilic molecules. The action mechanism of counterions has been investigated employing surface tension, viscosity, 1H NMR and fluorescence techniques.

Intermolecular Interactions of Polymer/Surfactants Mixture in Aqueous Solution Investigated by Various Techniques

The interaction between diblock copolymer with ionic surfactants in aqueous solution were studied employing surface tensiometery, electrical conductivity, steady-state fluorescence spectroscopy and dynamic laser light scattering at 303 K. Surface tension measurements were used to determine critical micelle concentration (CMC) and, thereby, its free energy of micellization (ΔGm), free energy of adsorption (ΔGads), surface excess concentration (Γ), and minimum area per molecule (A). The negative values of (ΔGm) both in case of SDS and CTAB confirmed the spontaneity of the processes. Conductivity measurements were used to determine critical micelle concentration (CMC), critical aggregation concentration (CAC), polymer saturation point (PSP), degree of ionization (α), and counterion binding (β). Addition of polymers could effectively reduce the CMC value of surfactants and, thus increase the detergency. Dynamic light scattering experiments were performed to check the changes in physiochemical properties of the block copolymer micelles take place due to the interactions of diblock copolymer with ionic surfactants. The ratio of (I1/I3) indicates the polarity of the pyrene micro environment and confirms the detection of micelle as well as polymer-surfactant interactions. Aggregation number (N), number of binding sites (n), and free energy of binding (ΔGb) for pure surfactants as well as for polymer-surfactant mixed micellar systems were determined by fluorescence quenching method.

Synthesis of new surface-active ammonium-type complexes based on palmitic acid for removing thin petroleum films from water surface

Complexes based on palmitic acid and nitrogen-containing compounds (monoethanolamine and triethylenetetramine) were synthesized. The synthesized complexes were taken to react with different moles of propylene oxide (1, 2 and 3) to form propoxylated compounds (surfactants). Some of physico-chemical indices of the prepared compounds such as solubility, acid and amine numbers as well as electrical conductivity have been determined. Surface-active properties (interfacial tension) of the obtained complexes were investigated by the stalagmometric method. Surface properties studied included critical micelle concentration (CMC), maximum surface excess (Γmax), and minimum surface area (Amin). Free energies of micellization (ΔGmic°) and adsorption (ΔGads°) were calculated. Petroleum-collecting and dispersing properties of the synthesized and propoxylated complexes in diluted (5wt.% aq. solution) and undiluted form in waters of varying salinity have been studied. FTIR spectra, C13 and H1NMR spectra confirm the compound structure.

Light scattering and surface tensiometric studies of tip-modified PEO-PBO diblock copolymers in water

The micellar and associative properties of four diblock copolymers, Me2N(CH2)2OE79B34 (denoted DE80B34), I−Me3N+(CH2)2OE79B34 (denoted TE80B34), I−Me3N+(CH2)2OE48B22 (denoted TE49B22), and HO(CH2)2OE62B22 (denoted E62B22), in aqueous solution and at various concentrations and temperatures, were investigated by surface tensiometry and dynamic and static laser light scattering. Surface tension measurements enabled the critical micelle concentration (CMC) to be determined at different temperatures, and thus the enthalpy of micellization (ΔHomic), the free energy of micellization (ΔGomic), and the entropy of micellization (ΔSomic) to be ascertained. Dynamic and static light-scattering measurements allowed the micellar parameters to be calculated and the extent of hydration of the copolymer micelle to be obtained qualitatively. The experimental results provided by these techniques are discussed in the terms of the variation in the hydrophilic to hydrophobic (E/B) ratio and end-group modification. Micellar parameters such as the weight-average molar mass (Mw), the association number (Nw), the thermodynamic radius (rt), and the hydrodynamic radius (rh) obtained from light-scattering data show that the micelles formed by the conventional EmBn and dimethylamino-tipped (DEmBn) copolymers are harder than those of trimethylammonium-tipped (TEmBn) copolymers. This difference in micellar properties is considered to be due to differences in polarity and charge effect at the hydrophilic ends of the tip-modified copolymers. The high value of rh for DEmBn and TEmBn copolymers as compared to E62B22 is an indication of micellar aggregation.

Effect of hydrophilic ionic liquid on aggregation behavior of aqueous solutions of sodium dodecylsulfate (SDS)

This paper delineates the change in aggregation behavior of aqueous sodium dodecylsulfate (SDS), an anionic surfactant upon addition of “hydrophilic” ionic liquid (IL) 3-methy-1-pentylimidazolium tetrafluoroborate in an increase in critical micelle concentration (cmc). The results demonstrate the presence of electrostatic and hydrophobic interactions between the ions of IL and the head group of the surfactant. From the cmc values and their temperature dependence, the thermodynamic parameters, viz. free energy of micellization (ΔGm0) and entropy of micellization (ΔSm0) were evaluated to permit speculation of the interactions existing in the studied aqueous surfactant-IL systems. Further, 1H NMR chemical shift measurements in micelle solutions containing IL have also been carried out. The results obtained are compared with the conclusions drawn from the conductance and fluorescence measurements.

Enhancing the Surface Properties of Some Amine Alginate Salts with Cationic Surfactant

Abstract In this paper different amine alginate salts were prepared by neutralization of alginic acid with amine compounds (triethanol amine, tri-isopropanol amine and hexamine). The chemical structures of the prepared compounds were confirmed using Gel Permeation Chromatography (GPC) and Fourier Transform Infrared Spectroscopy (FTIR). The surface properties of the target surfactants were studied and the surface parameters were determined; including surface tension, critical micelle concentration, maximum surface excess and minimum surface area, with and without addition of dodecytrimethyl ammonium bromide as a co-surfactant. Finally, the standard free energies of micellization and adsorption of the prepared surfactants were calculated. The obtained results indicated that, the adsorption activity of the three prepared alginate salts had increased by addition of very low concentration (0.0005 m/L) of DTAB surfactant, owing to the formation of an electrostatically stabilized Surfactant-Polyelectrolyte Complex.

In Vivo Anti-Leukemia, Quantum Chemical Calculations and ADMET Investigations of Some Quaternary and Isothiouronium Surfactants

Anti-leukemia screening of previously prepared isothiouronium and quaternary salts was performed, and some salts exhibited promising activity as anticancer agents. Quantum chemical calculations were utilized to explore the electronic structure and stability of these compounds. Computational studies have been carried out at the PM3 semiempirical molecular orbitals level, to establish the HOMO-LUMO, IP and ESP mapping of these compounds. The ADMET properties were also studied to gain a clear view of the potential oral bioavailability of these compounds. The surface properties calculated included critical micelle concentration (CMC), maximum surface excess (Γmax), minimum surface area (Amin), free energy of micellization (ΔGomic) and adsorption (ΔGoads).

The effect of type of self-assembled system and pH on the efficiency of corrosion inhibition of carbon-steel surfaces

In this work, three surfactants were used in the preparation of self-assembled systems to inhibit acidic corrosion on API5LX Gr X52 carbon-steel surfaces: CTAB (a cationic surfactant), SDS (an anionic surfactant), and C12E9 (a non-ionic surfactant). These surfactants were used in the form of aqueous solutions and in microemulsions. Pseudoternary diagrams were constructed using aqueous phases consisting of 0.5M NaCl at pH=2, 4 and 7, butan-1-ol as co-surfactant and kerosene as oil phase. The values of c.m.c., maximum surface excess, minimum surfactant cross-sectional area and free energy of micellization were determined using surface tensiometry. The distinct effects of pH and type of self-assembled system on the efficiency of corrosion inhibition have been elucidated by electrochemical techniques (polarization and Tafel curves). It has been demonstrated that these parameters can significantly affect the results, which depend largely on the mechanism of aggregate adsorption on the metal surface and droplet stability. By establishing the optimal conditions, excellent corrosion efficiencies were found for these systems, even at low surfactant concentrations.

Structure and Biological Behaviors of Some Metallo Cationic Surfactants

AbstractIn this study, different cationic surfactants were prepared by esterification with bromoacetic acid of different fatty alcohols, i.e., dodecyl, tetradecyl and hexadecyl species. The products were then reacted with diphenyl amine, and the resulting tertiary amines were quaternized with benzyl chloride to produce a series of quaternary ammonium salts. The metallocationic surfactants were prepared by complexing the cationic surfactants with nickel and copper chlorides. Surface tension of these surfactants were investigated at different temperatures. The surface parameters including critical micelle concentration (CMC), maximum surface excess (Γmax), minimum surface area (Amin), efficiency (PC20) and effectiveness (πCMC) were studied. The thermodynamic parameters such as the free energy of micellization () and adsorption (), enthalpy (), () and entropy (), () were calculated. FTIR spectra and 1H‐NMR spectra were obtained to confirm the compound structures and purity. In addition, the antimicrobial activities were determined via the inhibition zone diameter of the prepared compounds, which were measured against six strains of a representative group of microorganisms. The results indicate that these metallocationic surfactants exhibit good surface properties and good biological activity on a broad spectrum of microorganisms.

A comparative study of micellization with fluorinated and hydrogenated diquaternary ammonium bolaamphiphiles

Two new Na,Nb-Bis[3-(trimethylamino)propyl]-perfluoroalkanes diamide-Iodide with (a=1; b=10) and (a=1; b=12), differing by the fluorocarbon tail spacer (8 or 10 CF2), and the N1,N12-Bis[3-(trimethylamino)propyl]-dodecanediamide-Iodide have been synthesized in two steps involving the appropriate dimethyl perfluoro or hydrogeno alkane dicarboxylate, N,N-dimethyl-1,3-propane diamine, and methyl iodide. Their surface properties were studied at 45°C in aqueous solutions using conductivity, surface tension, and dynamic light scattering (DLS) measurements. A comparison of the micellar parameters usually obtained by these techniques has been carried out. The critical micelle concentrations (CMCs), the geometric packing parameters, the surface excess concentration, the area/surfactant molecule at the interface, the micellar ionization degree β and the free energies of micellization, the diffusion coefficient, and the hydrodynamic diameter were discussed. The effect of added KI on these parameters and on the size and on the kind of aggregates has been also investigated. The addition of 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) to the surfactant solutions, where the size of the complex DOPE-surfactant was determined by DLS over a wide range of concentrations, reveals a very different behavior comparing fluorinated and hydrogenated compounds.