Mixed Micellization Behavior of<Emphasis Type="Italic"> m</Emphasis>-2-<Emphasis Type="Italic">m</Emphasis> Gemini Surfactants with Some Conventional Surfactants at Different Temperatures

Mixed micellization behavior of dimeric cationic surfactants ethanediyl-1,2-bis(dimethyl alkyl ammonium bromide) (m-2-m where m = 10, 12) with conventional single chain cationic surfactants like cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), tetradecyl dimethyl benzyl ammonium chloride (C14BCl) and cetyl dimethyl benzyl ammonium chloride (C16BCl) were studied in aqueous and aqueous polyethylene glycol (PEG) solutions at 298.15, 308.15 and 318.15 K respectively using conductometric and viscometric methods. In aqueous solutions, all the combinations (except 12-2-12 + CTAB) were found to behave nonideally with mutual synergism which decreases with increase in temperature. Various thermodynamic parameters of micellization like \UpdeltaG_\textm^\texto {{\Updelta}}G_{\text{m}}^{\text{o}} , \UpdeltaH_\textm^\texto {{\Updelta}}H_{\text{m}}^{\text{o}} and \UpdeltaS_\textm^\texto {{\Updelta}}S_{\text{m}}^{\text{o}} were evaluated and discussed. Similarly in presence of PEG, the thermodynamic properties like \UpdeltaG_\textt^\texto {{\Updelta}}G_{\text{t}}^{\text{o}} , \UpdeltaH_\textt^\texto {{\Updelta}}H_{\text{t}}^{\text{o}} and \UpdeltaS_\textt^\texto {{\Updelta}}S_{\text{t}}^{\text{o}} associated with the transfer of surfactant monomers from the medium consisting of polymer-free mixed micelles to polymer-bound mixed micelles at various temperatures were also calculated. The negative values of \UpdeltaH_\textt^\texto {{\Updelta}}H_{\text{t}}^{\text{o}} show that aggregation process is more exothermic than micellization whereas the negative values of \UpdeltaS_\textt^\texto {{\Updelta}}S_{\text{t}}^{\text{o}} indicate that the presence of polymer bound mixed micelles decreases the degree of randomness of the system. Viscosity studies show that in aqueous solutions all the combinations of 10-2-10/12-2-12 display negative departure in the relative viscosity (η_r) from additivity rule which decreases with increase in temperature. Similarly in the presence of 5% PEG solutions the magnitude of the negative departure decreases for all the combinations and becomes positive in the case of C14BCl and CPC combinations with the studied gemini surfactants at higher temperatures.     

Synthesis and Properties of Novel Alkyl Sulfonate Gemini Surfactants

A series of novel dialkyl disulfonate gemini surfactants (2C_n-SCT where n is the carbon number of the hydrophobic chain) were synthesized from cyanuric chloride, aliphatic amine and taurine. The chemical structures of the prepared compounds were confirmed by ¹H NMR, ¹³C NMR, IR spectra, and ESI–MS. Their critical micelle concentrations (CMC) in the aqueous solutions at 25 °C were determined by surface tension and electrical conductivity methods. With the increasing length of the carbon chain, the values of their CMC initially decreased, and then increased with an alkyl chain length of 14. The surface tension measurements of 2C_n-SCT (except for n = 14) determined that there is a low CMC, a great efficiency in lowering the surface tension, and a strong adsorption at the air–water interface. In addition, adsorption and micellization behavior of 2C_n-SCT were estimated from pC ₂₀, the minimum average area per surfactant molecule (A _min), and standard free energy micellization and adsorption ( \Updelta G_\textmic^°  \textand \Updelta G_\textads^° \Updelta G_{\text{mic}}^{^\circ } \,{\text{and}}\,\Updelta G_{\text{ads}}^{^\circ } ). These properties are significantly influenced by the chain length n, and the adsorption is promoted more than the micellization.     

Surface and Biological Activity of Some Prepared Iminium Surfactants Based on Schiff Bases

A series of novel iminium surfactants were prepared through quaternization of different prepared fatty Schiff bases with benzyl chloride. The chemical structures were confirmed using FTIR, ¹H-NMR and mass spectroscopy. The surface properties and biological activity of these surfactants were investigated. The surface parameters including critical micelle concentration (CMC), maximum surface excess (Γ_max) and minimum surface area (A _min), Efficiency (PC₂₀) and Effectiveness (π_CMC) as well as the free energy of micellization ( $ \Updelta G_{\text{mic}}^{\text{o}} $ ) and adsorption ( $ \Updelta G_{\text{ads}}^{\text{o}} $ ) were calculated. It was found that the prepared compounds have good surface and biological activity.     

Structure and Biological Behaviors of Some Metallo Cationic Surfactants

In 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 (Γ _max), minimum surface area (A _min), efficiency (PC₂₀) and effectiveness (π _CMC) were studied. The thermodynamic parameters such as the free energy of micellization ( $\Updelta G_{\text{mic}}^{^\circ }$ ) and adsorption ( $\Updelta G_{\text{ads}}^{^\circ }$ ), enthalpy ( $\Updelta H_{\text{m}}^{^\circ }$ ), ( $\Updelta H_{\text{ads}}^{^\circ }$ ) and entropy ( $\Updelta S_{\text{m}}^{^\circ }$ ), ( $\Updelta S_{\text{ads}}^{^\circ }$ ) 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.     

Two New Organic–Inorganic Hybrids Based on [SiW12O40]4? Anion: Hydrothermal Syntheses, Crystal Structures, and Electrochemical Properties

Two new organic–inorganic hybrid compounds [\textCu^\textI ( \texten ) ₂ ( \textH ₂ \textO )] ₂ { ( \textSiW^\textVI _{1 1} \textW^\textV ₁\textO ₄₀ ) ₂ [ \textCu^\textII ( \texten ) ₂ ( \textH ₂ \textO )] ₂ [\textCu^\textII ( \texten ) ₂ ] ₂ }·6 \textH ₂ \textO [{\text{Cu}}^{\text{I}} \left( {\text{en}} \right)_{ 2} \left( {{\text{H}}_{ 2} {\text{O}}} \right)]_{ 2} \left\{ {\left( {{\text{SiW}}^{\text{VI}}_{ 1 1} {\text{W}}^{\text{V}}_{ 1}{\text{O}}_{ 40} } \right)_{ 2} \left[ {{\text{Cu}}^{\text{II}} \left( {\text{en}} \right)_{ 2} \left( {{\text{H}}_{ 2} {\text{O}}} \right)\left] {_{ 2} } \right[{\text{Cu}}^{\text{II}} \left( {\text{en}} \right)_{ 2} } \right]_{ 2} } \right\}{\cdot}6 {\text{H}}_{ 2} {\text{O}} (1) and (H₂ L)₂[SiW₁₂O₄₀]·H₂O (2) [en = ethylenediamine, L = 1,4-bis(3-pyridinecarboxamido)benzene], have been hydrothermally synthesized and characterized by IR, elemental analyses, TG analysis, and single-crystal X-ray diffraction. Structural analyses indicate that compound 1 exhibits an interesting three-dimensional(3D) cross-like supramolecular network through arrangement of a 1D organic–inorganic hybrid chain { ( \textSiW^\textVI _{1 1} \textW^\textV ₁ \textO ₄₀ ) ₂ [ \textCu^\textII ( \texten ) ₂ ( \textH ₂ \textO )] ₂ [\textCu^\textII ( \texten ) ₂ ] ₂ } ^2- . \left\{ {\left( {{\text{SiW}}^{\text{VI}}_{ 1 1} {\text{W}}^{\text{V}}_{ 1} {\text{O}}_{ 40} } \right)_{ 2} \left[ {{\text{Cu}}^{\text{II}} \left( {\text{en}} \right)_{ 2} \left( {{\text{H}}_{ 2} {\text{O}}} \right)\left] {_{ 2} } \right[{\text{Cu}}^{\text{II}} \left( {\text{en}} \right)_{ 2} } \right]_{ 2} } \right\}^{ 2- } . The compound 2 consists of protonated L ligand and [SiW₁₂O₄₀]⁴⁻ anion. The protonated L ligands have been extended into a 2D network via hydrogen-bonding interactions. The guest [SiW₁₂O₄₀]⁴⁻ clusters have been incorporated into the square voids of the 2D host network as templates. The electrochemical behavior and electrocatalysis of compound 2 bulk-modified carbon paste electrode (2-CPE) have been studied.     

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} ).     

Functionalization of cotton fabric orienting towards antibacterial activity

The primary objective of modifying cotton fabric was to impart bactericidal properties to attract various fields such as defence, space and textile industrial applications. Chemically initiated graft copolymerization of 4-vinyl pyridine (4-VP) and acrylonitrile (AN) onto cotton fabric was carried out using ceric ammonium nitrate as a redox initiator. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of concentration of initiator [CAN], concentration of nitric acid, monomer concentration, water, temperature and reaction time. Maximum grafting of 4-VP (51.63%) and AN (69.23%) was obtained respectively at optimum [ \textCAN ] = 2.738 ×10 ^{- 2} \left[ {\text{CAN}} \right] = 2.738 \times {10^{ - 2}} and 2.19 × 10⁻² moles/L, [ 4 - \textVP ] = 47.55 ×10 ^{- 22}\textmoles/\textL \left[ {4 - {\text{VP}}} \right] = 47.55 \times {10^{ - 22}}{\text{moles}}/{\text{L}} , [ \textAN ] = 18.85 ×10 ^{- 22}\textmoles/\textL \left[ {\text{AN}} \right] = 18.85 \times {10^{ - 22}}{\text{moles}}/{\text{L}} , [ \textHN\textO₃ ] = 11.9 ×10 ^{- 2} \left[ {{\text{HN}}{{\text{O}}_3}} \right] = 11.9 \times {10^{ - 2}} and 89.5 × 10⁻²² moles/L in 20 and 25 ml of water at an optimum temperature 70 °C and 60 °C with in 180 and 120 min. Antibacterial properties were induced into the modified cotton fabric by treating the grafted fabric with benzyl chloride. The grafted and quaternized copolymer were characterized by FTIR and Thermogravimetrical analysis. The bactericidal action of cotton fabric was tested by filtration test and it was observed that fabric grafted with 4-VP was more effective and efficient antibacterial as compared to AN grafted cotton sample.     

Micellization of Some Bile Salts in Binary Aqueous Solvent Mixtures

The micellization behavior of bile salts—sodium cholate and sodium deoxycholate was studied in aqueous methanol, ethanol and ethylene glycol mixtures (10–20 % v/v) over a temperature range (300–320 K) by surface tension and conductivity methods. Critical micelle concentration, extent of counter ion binding (α), interfacial property (A _min, ζ_max, π-CMC, $ \Updelta G_{\text{ad}}^{ \circ } $ ) and thermodynamic parameters ( $ \Updelta G_{\text{m}}^{ \circ } $ , $ \Updelta H_{\text{m}}^{ \circ } $ , $ \Updelta S_{\text{m}}^{ \circ } $ ) for the micellization process are reported and discussed.     

Structure and Spectral Characteristics of 3D-Supramolecular Coordination Polymers Based on Copper Cyanide and Dimethylquinoxaline

The reactions of K₃[Cu(CN)₄], R₃SnCl (R = Me or ph) and 2,3-dimethyl quinoxaline (dmqox) in H₂O/acetonitrile media at room temperature afford the 3D-supramolecular coordination polymers (SCP) ³_￥ [ \textCu ₂ ( \textCN ) ₂ \textdmqox ] ^{ 3}_{\infty } \left[ {{\text{Cu}}_{ 2} \left( {\text{CN}} \right)_{ 2} {\text{dmqox}}} \right] , 1 and ³_￥ [ \textCu ₂ ( \textCN ) ₄ ·( \textPh ₃ \textSn ) ₂ ·\textdmqox ] ^{ 3}_{\infty } \left[ {{\text{Cu}}_{ 2} \left( {\text{CN}} \right)_{ 4} \cdot \left( {{\text{Ph}}_{ 3} {\text{Sn}}} \right)_{ 2} \cdot {\text{dmqox}}} \right] , 2. The structure of the tin free 1 consists of parallel zigzag chains connected by dmqox to form 2D-sheets containing hexagonal 18-atom fused Cu₆(CN)₄(dmqox)₂ rings. The interwoven sheets along the a axis are close packed by extensive H-bonds developing 3D-network structure. The structures of 1 and 2 are investigated by elemental analysis IR, NMR and mass spectra. The ESI⁺ and ESI⁻ mass spectra of 2 support its polymeric nature while the ESI⁺ mass spectrum confirms the expected M. W. suggested by elemental analysis. The ¹³C-NMR spectrum of 2 supports the fact that the network structure of 2 contains the rhombic [Cu₂(μ₃-CN)₂] motif. The structure of 2 was compared with the structure of the reported prototype ³_￥ [ \textCu ₂ ( \textCN ) ₄ ·( \textPh ₃ \textSn ) ₂ ·\textqox ] ^{ 3}_{\infty } \left[ {{\text{Cu}}_{ 2} \left( {\text{CN}} \right)_{ 4} \cdot \left( {{\text{Ph}}_{ 3} {\text{Sn}}} \right)_{ 2} \cdot {\text{qox}}} \right] as well as the other related structures.     

The O<Subscript>2</Subscript> + NH<Subscript>3</Subscript> Reaction Over Rh(110): Steady State Kinetics and Oscillatory Behavior

Abstract  

The kinetics of ammonia oxidation with oxygen over a Rh(110) surface were studied in the pressure range 10⁻⁵–10⁻⁴ mbar. Nitrogen was found to be the preferred product at low partial pressures ratios \textp_{\texto 2} :\textp_{\textNH 3} {\text{p}}_{{{\text{o}}_{ 2} }} :{\text{p}}_{{{\text{NH}}_{ 3} }} , while the NO pathway was favored with oxygen rich gas mixtures and at high temperature. The reactive sticking coefficient of O₂ reaches up to 0.05 under steady state conditions. Pronounced hysteresis effects in the reaction rates were found in T-cycling experiments. Sustained oscillations in the reaction rates occurred under isothermal conditions at T = 620 K at a total pressure of 4 × 10⁻⁵ mbar.     

Influence of Turbidity Grade on Color and Appearance of Virgin Olive Oil

The appearance of most of the commercialized olive oils involves both their color and turbidity depending on the different technologies used for their elaboration. This research has been carried out to study the filtration impact on the colorimetric changes of virgin olive oils. Naturally turbid olive oils were blended at different proportions (100, 80, 60, 40, 20 and 0%) with their corresponding filtered replicates to obtain a scale of six levels of turbidity and simulating different turbidity grades. Tristimulus colorimetry, particularly the CIELAB uniform color, was used to follow color changes. As turbidity of the oil increased in the blend, yellowish oils, darker, and less saturated were obtained. Univariate correlations between the colorimetric parameters and turbid content were achieved with second degree polynomial equations, being chroma ( C_\textab ^* C_{{_{\text{ab}} }}^{ *} ) and hue (h _ab) the best correlated parameters. The color differences ( \Updelta E_\textab ^* \Updelta E_{{_{\text{ab}} }}^{ *} ) calculated between turbid oils (100%) and the consecutively decreasing turbid oils blends ranged from 3.18 to 18.72 CIELAB units, revealing differences in color visually perceptible to the human eye.     

Salt Effect on Mixed Micelle and Interfacial Properties of Conventional Cationic Surfactants and the Ionic Liquid Surfactant 1-Tetradecyl-3-methylimidazolium Bromide ([C14mim]Br)

The surface properties and mixed micellization behavior of binary combinations of an ionic liquid surfactant, namely, 1-tetradecyl-3-methylimidazolium bromide ([C₁₄mim]Br) with common cationic surfactants viz. tetradecyltrimethylammonium bromide and tetradecylpyridinium bromide in the presence of sodium bromide (NaBr) were investigated by surface tension and conductivity measurements. The critical micelle concentration (CMC) and interfacial parameters, such as the maximum surface excess (Γ_max), minimum area per molecule (A_min) and surface pressure at the CMC (π_CMC) were determined from the surface tension data. The CMC and Γ_max values were found to decrease with increasing salt concentrations. The $ \Updelta G_{\text{ad}}^{ \circ } $ and $ \Updelta G_{\text{m}}^{ \circ } $ values are negative indicating the spontaneity of micelle formation.     

Thermodynamics of Micellization of Sulfobetaine Surfactants in Aqueous Solution

The thermodynamics of micellization of the sulfobetaine (SB) amphoteric surfactants, that is N-alkyl-N,N-dimethyl-3-ammonio-1-propanesulfonate and N-alkyl-N,N-dimethyl-3-ammonio-1-butanesulfonate (the carbon atom number of the alkyl chain is 12, 14 and 16 respectively) in aqueous solution, have been studied by surface tension measurements with the temperature range from 298.15 to 318.15?K. The critical micelle concentrations (CMC) of SB n-3 and SB n-4 surfactants were determined from the drop-volume methods at different temperatures. The obtained results indicated that the values of critical micelle concentration strongly depended on the surfactants species and temperatures. Thermodynamic parameters ( $ \Updelta G_{\text{mic}}^{ \circ } $ , $ \Updelta H_{\text{mic}}^{ \circ } $ and $ \Updelta S_{\text{mic}}^{ \circ } $ ) of the micelle formation were determined. The micellization was found to be enthalpy-driven at lower temperatures, while this process was entropy-driven at higher temperatures. The enthalpy?Centropy compensation were also investigated. The compensation temperature T _c and $ \Updelta H_{\text{mic}}^{*} $ decreased, while $ \Updelta S_{\text{mic}}^{*} $ increased with the increase in the hydrophobic chain length.     

Soil nitrogen response to coupling cover crops with manure injection

Coupling winter small grain cover crops (CC) with manure (M) application may increase retention of manure nitrogen (N) in corn (Zea mays L.), -soybean [Glycine max (L.) Merr], cropping systems. The objective of this research was to quantify soil N changes after application of liquid swine M (Sus scrofa L.) at target N rates of 112, 224, and 336 kg N ha⁻¹ with and without a CC. A winter rye (Secale cereale L.)-oat (Avena sativa L.) CC was established prior to fall M injection. Surface soil (0–20 cm) inorganic N concentrations were quantified every week for up to 6 weeks after M application in 2005 and 2006. Soil profile (0–120 cm in 5, 20-cm depth increments) inorganic N, total N, total organic carbon and bulk density were quantified for each depth increment in the fall before M application and before the CC was killed the following spring. Surface soil inorganic N on the day of application averaged 318 \textmg  \textN  \textkg ^{- 1}_\textsoil 318\,{\text{mg}}\;{\text{N}}\;{\text{kg}}^{ - 1}{_{\text{soil}}} in 2005 and 186 \textmg  \textN  \textkg ^{- 1}_\textsoil 186\,{\text{mg}}\;{\text{N}}\;{\text{kg}}^{ - 1}{_{\text{soil}} } in 2006 and stabilized at 150 \textmg  \textN  \textkg ^{- 1}_\textsoil 150\,{\text{mg}}\;{\text{N}}\;{\text{kg}}^{ - 1}{_{\text{soil}}} in both years by mid-November. Surface soil NO₃-N concentrations in the M band were more than 30 times higher in the fall of 2005 than in 2006. The CC reduced surface soil NO₃-N concentrations after manure application by 32% and 67% in mid- November 2005 and 2006, respectively. Manure applied at 224 kg N ha⁻¹ without a CC had significantly more soil profile inorganic-N (480 kg N ha⁻¹) in the spring after M application than manured soils with a CC for the 112 (298 kg N ha⁻¹) and 224 (281 kg N ha⁻¹) N rates, and equivalent inorganic N to the 336 (433 kg N ha⁻¹) N rate. These results quantify the potential for cover crops to enhance manure N retention and reduce N leaching potential in farming systems utilizing manure.     

Investigation on conductivity of mixed surfactants reverse microemulsion

P-octyl polyethylene glycol phenyl ether (Triton X-100) and cetyltrimethylammonium bromide (CTAB) were mixed to be used as surfactant for preparing reverse microemulsion with n-hexane, n-hexanol and water. Effects of weight ratio of the two surfactants, temperature, concentrations of water and cosurfactant on the conductivity were studied. The results indicate that the conductivity of the mixed surfactants reverse microemulsion is greatly higher than that of the single surfactant system. The reverse microemulsion has been modified to be with good conductivity. The weight ratio of the two surfactants, temperature, concentrations of water and cosurfactant have obvious effects on the conductivity of the reverse microemulsion. Furthermore, the electrochemical behavior of potassium ferricyanide [K₃Fe(CN)₆] in the mixed surfactants reverse microemulsion was investigated by cyclic voltammetry. The result shows that the redox processes of \textFe( \textCN ) ₆ ^3- / \textFe( \textCN ) ₆ ^4- {{\text{Fe}}\left( {\text{CN}} \right)_{ 6}}^{ 3- } / {{\text{Fe}}\left( {\text{CN}} \right)_{ 6}}^{ 4-} present good reversibility and are controlled by diffusion in the system.     

Surface Adsorption and Aggregation Properties of Novel l-Lysine-Based Gemini Surfactants

Four chiral l-lysine-based gemini surfactants with different spacers were synthesized, namely, disodium (18R,23R)-12,20,21,29-tetraoxo-13,19,22,28-tetraazatetracontane-18,23-dicarboxylate([C₁₂-2-C₁₂]Na₂), disodium (18R,25R)-12,20,23,31-tetraoxo-13,19,24,30-tetraazadotetracontane-18,25-dicarboxylate([C₁₂-4-C₁₂]Na₂), disodium(18R,27R)-12,20,25,33-tetraoxo-13,19,26,32-tetraazatetratetracontane-18,27-dicarboxylate([C₁₂-6-C₁₂]Na₂), disodium(2R,2′R)- 2,2′-(6-chloro-1,3,5-triazine-2,4-diyl)bis(azanediyl)bis(6-dodecanamidohexanoate) ([C₁₂-T-C₁₂]Na₂). The chemical structures of the prepared compounds were confirmed by ¹H-NMR, ESI–MS and IR spectra. Further, the critical micelle concentration (CMC) of these surfactants in aqueous solutions was determined by surface tension and conductometry methods at 25 °C. Moreover, the adsorption and micellization behaviors of these surfactants were estimated by pC₂₀, the minimum average area per surfactant molecule (A_min), and standard free energy for micellization and adsorption ( \( \Updelta G_{\text{mic}}^{^\circ } \) and \( \Updelta G_{\text{ads}}^{^\circ } \) ). The results show that the four gemini surfactants have low CMC values and significantly low surface tension. Furthermore, the surfactants show strong adsorption at the air–water interface. The CMC and A_min values of the surfactants were found to be in the order of [C₁₂-2-C₁₂]Na₂ < [C₁₂-4-C₁₂]Na₂ < [C₁₂-6-C₁₂]Na₂ < [C₁₂-T-C₁₂]Na₂, which were in agreement with the sequence of \( \Updelta G_{\text{mic}}^{^\circ } \) and \( \Updelta G_{\text{ads}}^{^\circ } \) . The circular dichroism of the surfactants indicated the formation of chiral aggregates above the CMC values.     

Bifunctional N-Oxides of Alkyldiamidoamines

A homologous series of new surface-active 1,1-bis{[3-(N,N-dimethylamino)ethyl]-amido}alkane-di-N-oxides were synthesized in the reaction of an appropriate diethyl 2-alkylmalonate with N,N-dimethylethylenediamine followed by oxidation with an aqueous solution of hydrogen peroxide. The adsorption isotherms of their aqueous solutions were measured and evaluated to obtain adsorption parameters: critical micelle concentration (CMC), surface excess concentration (Γ_CMC), equilibrium surface tension at the CMC (γ _CMC), cross-sectional area of the adsorbed surfactant molecule (A _CMC), standard free energies of adsorption and micellization

Solubilization,Surface Active and Thermodynamic Parameters of Gemini Amphiphiles Bearing Nonionic Hydrophilic Spacers

A series of novel nine symmetric diquaternary gemini amphiphiles was synthesized having the formula:

Surface and Biological Activity of Organoammonium Hydrogen Selenite Surfactants

In this article we show steps taken toward the development of bactericidal and fungicidal synthetic cationic surfactants by the reaction of decyl, dodecyl or tetradecyl amine with selenious acid to produce a series of quaternary ammonium salts which consequently converted to copper and cobalt cationic complexes via complexing them with copper (II) or cobalt (II) ions. Surface properties of these surfactants were investigated. The surface properties studies included critical micelle concentration (CMC), maximum surface excess (Γ_max) and minimum surface area (A _min). Free energy of micellization ( ) and adsorption () were calculated. The antimicrobial activity was determined via the inhibition zone diameter of the prepared compounds measured against five strains of a representative group of microorganisms. FTIR spectra, elemental analyses and ¹ H-NMR spectra were obtained to insure the purity of the prepared compounds

Thermodynamic Properties of Sulfobetaine-Type Surfactants

Sulfobetaine-type surfactants containing a hydroxy group were synthesized by the reaction of long chain monoalkyl dimethyl tertiary amine with 3-chloro-2-hydroxypropanesulfonic acid sodium salt. The structures were characterized by ¹H NMR and ESI-MS. Their critical micelle concentrations (CMC) in aqueous solution were determined by the plate method in the temperature rang from 298.15 to 328.15 K. The thermodynamic parameters of micellization ( $\Delta G_{\text{mic}}^{\theta}$ , $\Delta H_{\text{mic}}^{\theta}$ and $\Delta S_{\text{mic}}^{\theta}$ ) and surface adsorption ( $\Delta G_{\text{ad}}^{\theta}$ , $\Delta H_{\text{ad}}^{\theta}$ and $\Delta S_{\text{ad}}^{\theta}$ ) were calculated from CMC data. The results showed that the micellization and surface adsorption of these surfactants in aqueous solution was a spontaneous and entropy-driven process. The micellization and surface adsorption became easier when the alkyl chain length increased from 12 carbon atoms to 14. The enthalpy–entropy compensation of micellization and adsorption was investigated. The compensation temperature were found to be (311 ± 2) K for both micellization and adsorption. The $\Delta H_{\text{mic}}^{*}$ and $\Delta H_{\text{ad}}^{*}$ decreased, but the $\Delta S_{\text{mic}}^{*}$ and $\Delta S_{\text{ad}}^{*}$ increased with increasing the hydrophobic chain length from 12 to 14.