Synthesis, Antimicrobial Activity and Micellization of Gemini Anionic Surfactants in a Pure State as Well as Mixed With a Conventional Nonionic Surfactant

New gemini anionic surfactants were prepared from sodium salts of monoalkyl sulfosuccinate esters of ethylene glycol having variably long tails (C₁₂, C₁₆, C₁₈) and dichloroethane. The chemical structures of the prepared surfactants were confirmed using different spectroscopic techniques. The surfaces tension values of the synthesized surfactants were measured at 25 °C individually or mixing at different molar fractions with ethoxylated alkylphenol. In all cases, mixed micellar aggregates were formed and critical micellar concentrations of binary mixtures containing different mole fractions of the surfactants were measured. The micellization processes of the individual and mixed surfactants were investigated. The effect of different alkyl chains of gemini anionic surfactants on properties of binary systems and molar ratio in the mixed aggregates were deduced. The critical micelle concentration of mixed surfactants shifted to lower values compared to those of the single surfactants. Effectiveness values increased with decreases in the mole fraction of gemini anionic surfactants. The negative values of interaction parameter (β) increased with increases in the chain length of anionic surfactants. The activity coefficient (f ₁, f ₂) and total minimum surface area of mixed solution were calculated. Also, the gemini anionic surfactants prepared have moderate antimicrobial activity towards bacteria and not active towards fungi.     

Micellar and Surface Properties of Some Monomeric Surfactants and a Gemini Cationic Surfactant

The physicochemical and interfacial properties of the monomeric surfactants cetyltrimethyl ammonium bromide (CTAB), cetyltriphenyl phosphonium bromide (CTPB), tetradecyl triphenyl phosphonium bromide (TTPB), cetyldiethylethanol ammonium bromide (CDEEAB), cetyltrimethyl ammonium chloride (CTACl), tetradecyltrimethyl ammonium bromide (TTAB), and a gemini surfactant (C₁₆-3-C_16, 2Br⁻) at different pH (3.1, 7.0, and 7.75) have been investigated by conductivity and surface tension measurements at 300 K. The critical micellar concentration (CMC), degree of micellar ionization (α), surface excess concentration (Г_max), minimum surface area per molecule of surfactant (A _min), Gibbs free energy of micellization (∆G _m⁰), surface pressure at the CMC (π _CMC), and the Gibbs energy of adsorption (∆G _ads⁰) of the monomeric surfactants have also been determined. The CMC, α and Г_max, increase with increasing pH whereas A _min decreases.     

Effect of Polar Organic Solvents on Self‐Aggregation of Some Cationic Monomeric and Dimeric Surfactants

Surface and micellization behavior of some cationic monomeric surfactants, viz., cetyldiethylethanolammonium bromide (CDEEAB), cetyldimethylethanolammonium bromide (CDMEAB), tetradecyldiethylethanolammonium bromide (TDEEAB) and dimeric surfactants, i.e., alkanediyl‐α, ω‐bis(dimethylhexadecylammonium bromide) (C₁₆‐s‐C₁₆, 2Br^? where s = 4, 12), butanediyl‐1,4‐bis(dimethyldodecylammonium bromide (C₁₂‐4‐C₁₂, 2Br^?) and 2‐butanol‐1,4‐bis(dimethyldodecylammonium bromide) (C₁₂‐4(OH)‐C₁₂, 2Br^?), was studied in water‐organic solvents [10 and 20 % v/v ethylene glycol (EG) and diethylene glycol (DEG)] by conductivity, surface tension and steady‐state fluorescence methods at 300 K. The main focus of the present work is on the study of the effect of organic solvents on the critical micelle concentration (CMC), Gibbs free energy of micellization (ΔG°_m), Gibbs free energy of transfer (ΔG°_trans), Gibbs adsorption energy (ΔG°_ads) and some interfacial parameters such as the surface excess concentration (Γ_max), minimum area per surfactant molecule (A_min) and surface pressure (π_CMC). The aggregation number (N_agg) and Stern‐Volmer quenching constant (K_SV) were also determined by the steady‐state fluorescence method. It was observed that N_agg decreased with increasing volume percent of organic solvent. The results exhibited an increase in CMC in water‐organic solvents as compared to the respective surfactants in pure water. The negative values of ΔG°_m and ΔG°_ads indicate a spontaneous micellization process. The thermodynamics of micellization revealed that the micellization‐reducing efficiency of glycols increases with the concentration and the number of ethereal oxygens in the glycol.     

Aggregation and Thermodynamic Properties of Some Cationic Gemini Surfactants

In this study, the gemini surfactants of the alkanediyl-α-ω-bis(alkyl dimethyl ammonium) dibromide type, on the one hand, with different alkyl groups containing m carbon atoms and an ethanediyl spacer, referred to as “m-2-m” (m = 10, 12 and 16) and, on the other hand, with n-C₁₆ alkyl groups and different spacers containing s carbon atoms, referred to as “16-s-16” (s = 2, 6, 10 and Ar (8)) have been synthesized, purified and characterized. The critical micelle concentration (CMC), micelle ionization degree (α) and Gibbs free energy of micellization (∆G _mic) of these surfactants and the monomeric cationic surfactants DTAB and CTAB have been determined by means of electric conductivity measurements. In addition, the temperature dependence of the CMC was determined for the 10-2-10 gemini surfactant. The CMCs of the gemini surfactants are found to be much lower than those of the corresponding monomeric surfactants and the effect of the hydrophobic alkyl chain length is more important than that of the spacer. The CMC of 16-s-16 passes through a maximum of (or around) s = 6 and then decreases for s = 10. The presence of a maximum CMC is explained by the contribution of a change of conformation of the surfactant with increasing spacer chain length. The changes of α with s and m are found qualitatively similar to those found for CMC values. The values of ∆G _mic are more negative for the dimers than for the monomers and also change with an increasing spacer carbon number, as CMC values do. The thermodynamic parameters of micellization indicate that the micellization of 10-2-10 is enthalpy driven.     

Studies on the Effect of Amino Acids/Peptide on Micellization of SDS at Different Temperatures

Conductivities of (0.001–0.012) m sodium dodecyl sulfate have been determined in water and in the presence of 0.10 m aqueous glycine/alanine/glycylglycine at 298.15, 303.15, 308.15, and 313.15 K. From the specific conductivity data, the critical micellar concentration, degree of counter ion association, degree of counterion dissociation, free energy of transfer of hydrophobic chain from the medium to interior of the micelle, and surface contribution, standard free energy of micellization, standard enthalpy of micellization, and standard entropy of micellization of sodium dodecyl sulfate have been computed. The thermodynamic parameters of micellization and the effect of additives on these parameters have been used to study the interactions present in the micellar systems.     

Sugar-based cationic surfactants: Synthesis and aggregation of methyl 2-acylamido-6-trimethylammonio-2,6-dideoxy-d-glucopyranoside chlorides

The synthesis of the sugar-based cationic surfactants methyl 2-acylamido-6-trimethylammonio-2,6-dideoxy-d-glucopyranoside chlorides is reported here. Aggregation of these surfactants (predominantly α anomers) in water was studied at 25°C by conductivity measurements. Increasing the chain length of the amido group R decreased the critical micelle concentration (CMC) and the degree of counter-ion dissociation. The dependence of the Gibbs' free energy of micellization and CMC on the length of R is similar to that observed for other ionic surfactants. The free energy of transfer of the head group, i.e., cationic amino sugar moiety, from water to the micelle is more negative than that of other ionic surfactants, including sodium methyl 2-acylamido-2-deoxy-6-O-sulfo-d-glucopyranosides, probably due to a combination of a micellar “medium” effect and intermolecular H-bonding in the micellar pseudophase.     

Synthesis and Study of the Surface Properties of Alkylnaphthalene and Alkylphenanthrene Sulfonates

Some alkylnaphthalene and alkylphenanthrene sulfonates were synthesized by means of a Wurtz–Fittig reaction. The HLB values for the prepared compounds were calculated, and the basic properties were studied in water at different temperatures, namely, 25, 35 and 45 °C. Through surface tension measurements, the following values were determined: the critical micelle concentration (CMC) and the surface tension at the CMC (γ_CMC). The following values were calculated: area per molecule at the CMC (A_CMC), standard free energy change of micellization (ΔG _mic), standard free energy of adsorption (ΔG _ad), and the efficiency of a surfactant in reducing surface tension (pC20). Furthermore, the partition coefficients of the synthesized compounds were also measured. The results show that n-alkylnaphthalene and n-alkylphenanthrene surfactants studied exhibit desirable properties that may be of value in some fields such as detergency. To confirm the detergency power of the prepared surfactants, some foam studies were performed.     

Effect of aromatic ring in the alkyl chain on surface properties of arylalkyl surfactant solutions

Surface properties of two series of anionic arylalkyl surfactants, containing different aromatic rings in the straight aliphatic chain, sodium N-aryloleyl-N-methyl-2-aminoethanesulfonates and sodium N-aryloleyl p-methoxyanili-nesulfonates, were investigated. An increase of the aromatic ring size in the alkyl chain increases the critical micelle concentration (CMC) and surface tension at CMC. However, this also decreases the efficiency and effectiveness in reducing water surface tension. The dominant factor of the decrease of efficiency and effectiveness is attributed to the function of the hydrophilic segment and hydrophobic segment for arylalkyl surfactants, respectively. The same results are found in the standard free energy of adsorption (ΔG ^o _ads) and the standard free energy of micellization (ΔG ^o _mic) values. Moreover, with the increase of the aromatic ring size, the adsorption and micellization of arylalkyl surfactants begin to weaken. The data indicate that some parts of surface properties for arylalkyl surfactants are affected by the bulkiness of the arylalkyl chain. The results provide opportunities for further detailed examination of surface properties of arylalkyl surfactants with other branched alkyl chains.     

Physico-Chemical Investigations of Mixed Micelles of Cationic Gemini and Conventional Surfactants: a Conductometric Study

The interaction of cationic gemini and cationic conventional surfactants by conductivity was systematically overviewed, paying attention to synergism observed in micellization. These mixed systems were found to show remarkable synergism in micelle formation. The experimental critical micelle concentration values being lower than the value predicted by ideal solution theory indicate that the mixed micellization is due to attractive interaction between the two components. Gemini/conventional systems form mixed micelle due to attractive interactions (negative β values). The values of micellar mole fraction of constituent 1 (X ₁) in surfactant mixtures are more than in the ideal state (X ₁ ^ideal ), which means that, the mixed micelles are rich in conventional surfactants in comparison to that in the ideal state.     

Micellization of Cetyl Triphenyl Phosphonium Bromide Surfactant in Binary Aqueous Solvents

The effect of the different binary aqueous organic solvents viz. 1,4-dioxane, acetonitrile, dimethylsulfoxide, ethylene glycol, and methanol, on the micelle formation and thermodynamics of a cationic surfactant cetyl triphenyl phosphonium bromide has been studied conductometrically at 298–318 K. From the conductivity data critical micelle concentration, degree of counter ion dissociation (α) and thermodynamic parameters of micellization have been determined. It is observed that micellization tendency of the surfactant decreases in the presence of binary aqueous solvents. The entropies of micellization are all positive, and they compensate the enthalpies of the process.

Synthesis and surface properties of oxyethylenated 2-alkyl-5-hydroxymethyl-5-ethyl-1,3-dioxanes

In acid-catalyzed reactions of long chain aliphatic aldehydes (I) (R=n−C₇H₁₅; n−C₉H₁₉; n−C₁₁H₂₃) with 1,1,1-tris(hydroxymethyl)propane (II), 2-alkyl-5-hydroxymethyl-5-ethyl-1,3-dioxanes (III) were obtained. The latter were then reacted with ethylene oxide in the presence of sodium methoxide. Three series of oxyethylenated cyclic acetal derivatives (IV) were obtained. They constitute a new group of chemodegradable surfactants which readily hydrolyze and oxidize in natural water reservoirs. Physical data of the new compounds and some surface properties such as cloud points (Cp), critical micelle concentrations (cmc), changes of free energy of micellization, (ΔG°_cmc), surface tensions of aqueous solutions near cmc, γ_min, and wetting and foaming properties, were determined. The surfactants (IV) have aqueous solution properties similar to those of oxyethylenated longchain aliphatic alcohols. It is shown that the micellization of surfactants (IV), expressed in terms of ΔG°_cmc, depends both on the length of the aliphatic chain at the C-2 carbon atom and on the presence of ethyl group at C-5 of 1,3-dioxane ring which enhances the hydrophobic character of derivatives (III). Hence, the surfactants have a higher surface activity than oxyethylenated 2-alkyl-4-hydroxymethyl-1,3-dioxolanes or 2-alkyl-5,5-bis-(hydroxymethyl)-1,3-dioxanes. The use of 2-alkyl-5-hydroxymethyl-5-ethyl-1,3-dioxanes (III) in surfactant synthesis is an example of applying hydrophobic intermediates obtained from aldehydes only. This, and the chemodegradability mentioned make the compounds a very interesting group of new surfactants. Part XVII in the series: Chemical Structure and Surface Activity.     

Effects of Molecular Structure and Temperature on Micellization of Cationic Ammonium Gemini Surfactants in Aqueous Solution

Micellization of four cationic quaternary ammonium gemini surfactants, having a diethyl ether or hexyl spacer with the alkyl chain lengths of 12 and 16 carbon atoms, was studied using isothermal titration microcalorimetry (ITC) and electrical conductivity measurements in the temperature range from 298.15 to 313.15 K. In this temperature range, where surfactants are normally applied, the temperature almost does not influence the critical micelle concentration (CMC) and the degree of micelle ionization (α) values of the gemini surfactants, and the replacement of a hexyl spacer by a diethyl ether spacer leads to a slight decrease in the CMC and α values. However, as the alkyl chain length increases from 12 to 16 carbon atoms, the CMC values significantly decrease from 0.99–1.19 mM to 0.020–0.057 mM. In particular, the enthalpy of micellization (ΔH_mic ) and the associated thermodynamic parameters show obvious changes with varying temperature and molecular structure. ΔH_mic becomes much more exothermic at higher temperature or for the surfactants with a more hydrophilic spacer. Moreover, the heat capacity change of micellization (ΔC _{P, mic} ) is less exothermic for the surfactants with a more hydrophilic spacer or a longer alkyl chain. The enthalpy–entropy compensation data show that the surfactants with longer alkyl chains have a more stable micellar structure.     

Synthesis and some studies on fluorinated cationic surfactants: surface and biocidal activities

Three fluorinated cationic surfactants were prepared by condensing N-(2-bromoethyl)perfluoroalkylamides with stoichiometric amounts of pyridine, triethanolamine, and triethylamine to produce three quaternary ammonium salts. The surface and biocidal properties of these surfactants were investigated to find the relation between the structure of the hydrophilic portion of the compounds and their efficiency as biocides. The properties studied included critical micelle concentration (CMC), effectiveness (II_CMC), surface excess concentration (T_max), and area occupied by a molecule (A_min). Free energies of micellization (ΔG _mic ^o) and adsorption (ΔG _ads ^o) of the surfactants in aqueous solution were calculated. The minimal inhibitory concentrations of the prepared compounds were tested against five strains as representative group of microorganisms.     

Influence of Spacer Nature on the Aggregation Properties of Anionic Gemini Surfactants in Aqueous Solutions

A series of anionic gemini surfactants with the same structure except the spacer nature have been studied. Their solution properties were characterized by the equilibrium surface tension and intrinsic fluorescence quenching method. The critical micelle concentrations (CMC), surface tension at cmc, C₂₀, and the micelle aggregation number (N) were obtained. The surface tension measurements indicate that these gemini surfactants have much lower cmc values and great efficiency in lowering the surface tension of water compared with those of conventional monomeric surfactants. Furthermore, the standard free energy of micellization for anionic gemini surfactants was also determined. The results showed that the nature of the spacer has an important effect on the aggregation properties of gemini surfactants in aqueous solutions. The surfactant with a hydrophilic, flexible spacer was more readily able to form micelle compared with the surfactant with a hydrophobic, rigid spacer, which leads to a lower CMC value, larger N, more negative free energy of micellization, and a more closely packed micelle structure.     

Synthesis of Ethoxylated Alkyl Sulfosuccinate Surfactants and the Investigation of Mixed Solutions

A series of ethoxylated sodium monoalkyl sulfosuccinate (ESMASS) ester surfactants were prepared by reacting polyethylene glycol (molecular weight 600) with sodium monoalkyl sulfosuccinate (SMASS). The esters were prepared by reacting octyl, lauryl, or cetyl alcohol with sodium sulfosuccinate (SSS) to prepare E(14)SMOSS, E(14)SMLSS, and E(14)SMCSS. The chemical structures of the prepared surfactants were confirmed by Fourier transform infrared (FTIR) and ¹H-NMR spectroscopy. The surface tension of the synthesized surfactants was measured at 25 °C individually or mixing at different molar fractions with sodium dioctyl sulfosuccinate. The surface active properties were calculated and the micellization process of the mixture was investigated. The molar ratio of anionic (SDOSS) and anionic–nonionic surfactant moieties [E(14)SMOSS, E(14)SMLSS, and E(14)SMCSS] in the mixed aggregates were deduced using the regular solution approximation equations. Depending on the critical micelle concentration values measured for each surfactant individually, and as well as the mixed systems, the minimum surface tension was exhibited at a ratio of 0.6 SDOSS:0.4 E(14)SMCSS. The micellar composition of the mixed aggregates were explained and discussed based on the effect of their chemical structures. The activity coefficient (f ₁, f ₂), interaction parameter (β), and ideality of anionic–nonionic mixed aggregates were evaluated.

Solubilization of Ni Imidazole Complex in Micellar Media of Anionic Surfactants,Sodium Dodecyl Sulfate and Sodium Stearate

The solubilization and physicochemical behavior of a coordination complex of nickel, namely [Ni(im)₆]F₂·5H₂O [hexakis(imidazole)nickel(II) fluoride pentahydrate], in aqueous micellar media of anionic surfactants, i.e., sodium dodecyl sulfate (SDS) and sodium stearate (SS), were investigated by using UV–Vis spectroscopy and electrical conductivity measurements. Spectroscopic techniques were used for the computation of binding constant (K_b), partition coefficient (K_x), change in free energy of binding (ΔG_b), and change in free energy of partition (ΔG_p), whereas electrical conductivity data was helpful to calculate thermodynamic parameters of micellization of surfactants in the presence of the Ni complex, i.e., standard entropy of micellization (ΔS_m), free energy (ΔG_m), and enthalpy of micellization (ΔH_m). It is evident from the results that solubilization of the Ni complex takes place because of electrostatic as well as hydrophobic interactions. The presence of the Ni complex in micellar media increases the critical micelle concentration of both surfactants owing to the structure‐breaking effect.     

Preparation and Application of Fluorinated Cationic Surfactants

Four fluorinated cationic surfactants were prepared by condensing 2,2,3,3, tetrafluoro-1-propyl chloroacetate with stoichiometric amounts of pyridine, 2-hydroxypyridine, 8-hydroxyquinoline and 8-hydroxyquinaldine to produce four quaternary ammonium salts. The surface and biocidal properties of these surfactants were investigated. Surface properties of their solutions including surface tension, critical micelle concentration (CMC), effectiveness (Π_cmc), maximum surface excess (Γ_max) and minimum surface area (A _min) were investigated with respect to different concentrations at 25 °C. Standard free energies of micellization and adsorption of the prepared surfactants in the aqueous solution were studied. The biocidal activity was determined via the inhibition zone diameter of prepared compounds which tested against six strains as a representative group of microorganisms.

Synthesis and study of the surface properties of long-chain alkylnaphthalene sulfonates

Long-chain alkylnaphthalene sulfonates were synthesized by means of a Wurtz-Fittig reaction, and the basic properties were studied in water at 30°C. Through surface tension measurements, the following values were determined: the critical micelle concentration (CMC) and the surface tension at the CMC (γ_CMC). The following values were calculated: area per molecule at the CMC (A_CMC), standard free energy change of micellization (ΔG _mic ^o ), standard free energy of adsorption (ΔG _ad ^o ), and the “efficiency” of a surfactant in reducing surface tension (pC₂₀). The micelle aggregation numbers were measured through steady-state fluorescence-quenching methods. As the chain length of the hydrocarbon of n-alkylnaphthalene sulfonate increased, the Krafft temperature increased, the surface tension decreased, the value of CMC decreased, pC₂₀ increased, ΔG _ad ^o and ΔG _mic ^o became more negative, and the micelle aggregation number increased. The results showed that sodium α-(n-decyl)naphthalene sulfonate (DNS) had a high pC₂₀, low Krafft temperature, and lower CMC than other surfactants in this study. Thus, DNS and the other n-alkylnaphthalene surfactants studied exhibit desirable properties that may be of value in some fields such as detergency, oil recovery, and dyes.     

Preparation of a New Oligomeric Surfactant: N,N,N′,N″,N″-Pentamethyl Diethyleneamine—N,N″-Di-[Tetradecylammonium Bromide] and the Study of its Thermodynamic Properties

A new oligomeric surfactant: N,N,N′,N″,N″- pentamethyl diethyleneamine—N,N″-di-[tetradecylammonium bromide] referred to as 14-2-N(CH₃)-2-14 was synthesized, purified and characterized by Elemental Analysis, ¹H and ¹³C NMR and Electrospray. The micellar properties of this compound were determined by electrical conductivity and surface tension methods. Optical microscopy was also employed to study the behavior of anhydrous surfactant and the binary water/surfactant system as a function of temperature. The critical micellar concentration (cmc), degree of counterion binding and thermodynamic parameters of micellization (standard molar Gibbs energy, enthalpy and entropy of micellization) were determined by electrical conductivity measurements in the temperature range [24–54 °C]. Surface tension measurements also provide information about the dependence of the surface tension at the cmc (γ_cmc), pC₂₀ (negative logarithm of the surfactant’s molar concentration C₂₀, required to reduce the surface tension by 20 mN/m, the surface excess (Γ_max) at air/solution interface, the minimum area per surfactant molecule at the air/solution interface (Amin), surface pressure at the cmc (П_cmc), critical packing parameter(CPP) and the standard free energies of micellization ( \Updelta G_m⁰\Updelta G_{m}^{0}) and of adsorption ( \Updelta G_\textads⁰ \Updelta G_{\text{ads}}^{0} ).     

Aggregation and adsorption behavior of cobalt-based metallosurfactant in water–ethylene glycol media forming worm-like micelles

The cobalt based metallosurfactant cis-chlorobis(ethylenediamine)hexadecylaminecobalt(III) chloride (CHCC) has been prepared and well characterized by utilizing elemental analysis, NMR (¹H, ¹³C), FT-IR and UV–Vis spectroscopy. The CHCC metallosurfactant shows thermal stability up to 168°C. The micellization behavior of the synthesized CHCC metallosurfactant has been investigated systematically by the tensiometric, conductometric, and fluorescence techniques. The critical micelle concentration (cmc) values of CHCC have been determined in various water–ethylene glycol mixtures ranging from 0 to 100 weight % of ethylene glycol at 293.15, 298.15, 303.15, and 308.15 K. The physicochemical parameters namely counterion binding constant, surface pressure, surface excess, surface area covered per CHCC metallosurfactant molecule, free energy minimum, standard free energies of micellization and adsorption, standard enthalpy and entropy of micellization, and Gibb's free energy of transfer have been calculated. The hydrodynamic diameters and zeta potentials of the CHCC metallomicelles have been measured by dynamic light scattering method. Transmission electron microscopy was employed to confirm the presence of worm-like micelles.