Novel Ester-linked Anionic Gemini Surfactant: Synthesis,Surface-Active Properties and Antimicrobial Study

A novel anionic gemini surfactant containing an ester bond in the spacer group was synthesized using cardanol as the raw material and characterized by IR, ¹H NMR and ¹³C NMR. The surface properties of the gemini surfactant were investigated and compared with its corresponding single chain surfactant counterpart. It was found that this novel gemini surfactant exhibited a low critical micelle concentration value (1.9 mM) and good efficiency in reducing surface tension of water (33.6 mN/m). The gemini surfactant was found to have antimicrobial activity against Gram-negative (Escherichia coli and Pseudomonas aeruginosa), Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacteria and fungi (Aspergillus niger, Aspergillus flavus, Candida albicans and Rhizopus stolonifer). The gemini as well as the corresponding single chain surfactant showed good antimicrobial activity against all pathogenic microorganisms studied and can be employed as an antimicrobial agent. The synthesized novel anionic gemini surfactant possesses an excellent wettability and low foamability.     

Synthesis and Properties of 4,4′-Di(<Emphasis Type="Italic">n</Emphasis>-Tetradecyl) Diphenyl Methane Disulfonate Salt

The gemini surfactant, sodium 4,4′-di(n-tetradecyl) diphenyl methane disulfonate, has been synthesized in four steps with high yield and only one isomer. The structures of intermediate products were analyzed by ¹H-NMR spectrometry and elemental analysis. Mass spectrometry was applied to the analysis of the final product. The Krafft point, surface tension, and critical micelle concentration of the aqueous solution and the oil–water interfacial tension were measured. The results indicate that the gemini surfactant exhibits an ultra-low interfacial tension of 7.22 × 10^?3 mN/m, which shows potential applications for enhanced oil recovery.     

Synthesis,Surface Activities and Toluene Solubilization by Amine-oxide Gemini Surfactants

A series of amine-oxide gemini surfactants featuring amide groups [N, N’-dimethyl-N, N’-bis(2-alkylamideethyl)-ethylenediamine oxide (alkyl = C₁₁H₂₃, C₁₃H₂₇, C₁₅H₃₁, C₁₇H₃₅)] have been synthesized via a three-step synthetic route, and their chemical structures were confirmed by mass spectra, FTIR and ¹H-NMR spectra. The surface activities of these compounds have been measured. The results show that these synthesized amine-oxide gemini surfactants reduced the surface tension of water to a minimum value of approximately 26.91 mN m^?1 at a concentration of 2.92 × 10^?5mol L^?1. Furthermore, their critical micelle concentration (CMC) values and solubilization of toluene decrease with an increase of the hydrophobic chain length from 12 to 18. Isoelectric point measurements revealed that their pI values range from 4.0 to 10.5.     

Novel amphiphilic temperature responsive graft copolymers PCL-<Emphasis Type="Italic">g</Emphasis>-P(MEO<Subscript>2</Subscript>MA-<Emphasis Type="Italic">co</Emphasis>-OEGMA) via a combination of ROP and ATRP: synthesis,characterization, and sol-gel transition

A series of well-defined novel amphiphilic temperature-responsive graft copolymers containing PCL analogues P(αClεCL-co-εCL) as the hydrophobic backbone, and the hydrophilic side-chain PEG analogues P(MEO₂MA-co-OEGMA), designated as P(αClεCL-co-εCL)-g-P(MEO₂MA-co-OEGMA) have been prepared via a combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The composition and structure of these copolymers were characterized by ¹H NMR and GPC analyses. The self-assembly behaviors of these amphiphilic graft copolymers were investigated by UV transmittance, a fluorescence probe method, dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. The results showed that the graft copolymers exhibited the good solubility in water, and was given the low critical temperature (LCST) at 35(±1) °C, which closed to human physiological temperature. The critical micelle concentrations (CMC) of P(αClεCL-co-εCL)-g-P(MEO₂MA-co-OEGMA) in aqueous solution were investigated to be 2.0 × 10^?3, 9.1 × 10^?4 and 1.5 × 10^?3 mg·mL^?1, respectively. The copolymer could self-assemble into sphere-like aggregates in aqueous solution with diverse sizes when changing the environmental temperature. The vial inversion test demonstrated that the graft copolymers could trigger the sol-gel transition which also depended on the temperature.     

Synthesis,Characterization and Surface Properties of Amidosulfobetaine Surfactants Bearing Odd-Number Hydrophobic Tail

Three amidosulfobetaine surfactants were synthesized namely: 3-(N-pentadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2a); 3-(N-heptadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2b), and 3-(N-nonadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2c). These surfactants were prepared by direct amidation of commercially available fatty acids with 3-(dimethylamino)-1-propylamine and subsequent reaction with 1,3-propanesultone to obtain quaternary ammonium salts. The synthesized surfactants were characterized by IR, NMR and mass spectrometry. Thermogravimetric analysis (TGA) results showed that the synthesized surfactants have excellent thermal stability with no major thermal degradation below 300 °C. The critical micelle concentration (CMC) values of the surfactants 2a and 2b were found to be 2.2 × 10^?4 and 1.04 × 10^?4 mol/L, and the corresponding surface tension (γ_CMC) values were 33.14 and 34.89 mN m^?1, respectively. The surfactants exhibit excellent surface properties, which are comparable with conventional surfactants. The intrinsic viscosity of surfactant (2b) was studied at various temperatures and concentrations of multi-component brine solution. The plot of natural logarithm of relative viscosity versus surfactant concentration obtained from Higiro et al. model best fit the surfactant behavior. Due to good salt resistance, excellent surface properties and thermal stability, the synthesized surfactant has potential to be used in various oil field applications such as enhanced oil recovery, fracturing, acid diversion, and well stimulation.     

Synthesis and Surface Active Properties of a Gemini Imidazoline Amphoteric Surfactant

The gemini imidazoline amphoteric surfactant was prepared in two steps. We first reacted lauric acid and triethylenetetramine to obtain the intermediate called bisalkyl-bis-imidazoline. We analyzed it by ¹H NMR, and the yield was 82.45 % according to perchloric acid non-aqueous titration. The intermediate was then quaternized using sodium 2-chloroethanesulfonic acid in a mixture of isopropyl alcohol and water, during which we controlled the pH between 8 and 9 and the temperature between 80 and 90 °C to prepare C12-bis-imi. The air–liquid surface tension was measured by a tensiometer at 298 ± 0.1 K. The results show that the critical micelle concentration (CMC) was 2.25 × 10^?3 mol/L and the surface tension at the CMC (γ _CMC) was 30.42 mN/m. C12-bis-imi showed a synergistic effect in combination with lauric alcohol with nine ethylene oxide groups (AEO9). The synergistic effect is most striking when the mole ratio of C12-bis-imi/AEO9 was 1/1, and the corresponding CMC was 9.79 × 10^?5 mol/L and the γ _CMC was 37.61 mN/m.     

Itaconic Acid Based Surfactants: I. Synthesis and Characterization of Sodium <Emphasis Type="Italic">n</Emphasis>-Octyl Sulfoitaconate Diester Anionic Surfactant

A novel itaconate-based surfactant, namely sodium n-octyl sulfoitaconate diester (SOSID), has been synthesized from itaconic acid (IA) and n-octanol by sulfonation and esterification reaction processes. The effects of reaction temperature, reaction time, molar ratios of n-octanol to IA and the catalyst dosage on the esterification were investigated. The chemical structure of the surfactants SOSID was characterized by means of LC–MS and confirmed by FT-IR and ¹H NMR spectroscopy. The surface tension γ and the critical micelle concentration (CMC) were determined as 25.02 mN/m and 4.0 × 10^?4 mol/L by using surface tensiometer at 20 °C. Further investigations showed that SOSID possess excellent wetting, emulsifying and lime soap dispersing properties.     

Synthesis and Characterization of Novel Aryl Alkyl Sulfonates Based on Nonylphenol

A series of nonylphenol-substituted alkyl sulfonates (C _x NPAS, x = 8, 10, 12, 14, 16) with two hydrocarbon chains and two different hydrophilic groups has been synthesized from α-olefins and nonylphenol. The respective products have a “pseudo-gemini” surfactant structure. The structures of the C _x NPAS have been characterized by IR, UV, ¹H nuclear magnetic resonance, electrospray ionization mass spectrometry, and elemental analysis. The effects of carbon chain length of the obtained surfactants on properties such as the critical micelle concentrations (CMC) in aqueous solutions, surface tension at the CMC (γ _CMC), and efficiency of adsorption at the water/air interface (pC ₂₀) have been determined. The γ _CMC of the surfactants first decreased and then increased with increasing length of the carbon chain x, and reached a minimum of 29.25 mN/m at x = 10, which is much lower than that of α-olefin sulfonate (AOS) (33.52 mN/m). The CMC decreased and pC ₂₀ increased with increasing x. The introduction of the hydroxyl group is responsible for multiple molecular conformations at the water/air interface and leads to a greater molecular area A _min and smaller Γ_max than those of AOS.     

Zinc Corrosion in Acidic Solutions Containing Single and Mixed Surfactants

The influence of surfactant synergism on Zn corrosion inhibition in 0.1-M HCl aqueous solutions has been determined at room temperature. Solutions of single and mixed surfactants consisting of sodium dodecylsulfate (SDS) and N,N-dimethyldodecan-1-amine oxide (DDAO) in water and in 0.1-M HCl were also prepared at room temperature. Critical micelle concentration (CMC) data were obtained through surface tension measurements as a function of mixing composition. A regular solution model was considered to analyze CMC values. The interaction parameter (β), the composition of mixed micelles (x) and the activity coefficients (f) were estimated by a regular solution model for all amphoteric–anionic mixed systems. β Vvalues showed synergism for the binary mixtures of these solutions in the absence and presence of 0.1-M HCl at all investigated compositions. Zinc corrosion in single and binary SDS/DDAO mixed solutions at 5-mM total surfactant concentrations in the presence of 0.1-M HCl was also investigated at static and dynamic conditions. The weight loss data revealed corrosion inhibition activity obeyed the following order: binary (0.75 DDAO + 0.25 SDS) > binary (0.50 DDAO + 0.50 SDS) > single DDAO > single SDS, suggesting an enhancement in the corrosion inhibition activity of DDAO in the presence of a proper amount of SDS. Conductivity time measurements show a similar trend as that obtained by a weight loss method at (0.50 DDAO + 0.50 SDS). The results were illustrated on the basis of synergistic interaction between the mixed surfactants.     

Synthesis and Surface Activities of Novel Succinic Acid Double-Tailed Sulfonate Fluorinated Surfactants

In this study, four environmentally friendly succinic acid double-tailed sulfonate fluorinated surfactants were synthesized from maleic anhydride, fluoroalkyl alcohols, namely 1-(1H,1H,7H-Dodecafluoroheptyloxy) ethanol, 1-(1H,1H,5H -octafluoropentyloxy) ethanol, 1-(1H,1H,3H-tetrafluoropropoxy) ethanol, and 1-(1H,1H -trifluoroethyoxy) ethanol, and sodium hydrogensulfite. The surfactant structure was characterized by FT-IR, ¹H NMR, and ¹⁹F NMR . Thermogravimetric results showed that the fluorinated surfactants were stable up to relatively high temperature. The Krafft points of the four novel succinic acid double-tailed sulfonate fluorinated surfactants were all below 0 °C. The lowest CMC value for the synthesized four double-tailed fluorine surfactants is about 0.076 mmol L^?1, far less than that of ammonium perfluorooctanoate (PFOA), demonstrating that double-tailed surfactants have higher surface activity than surfactants with one fluoroalkyl chain. The replacement of alkyl groups with oxyethylene groups enhances the hydrophilicity of the obtained fluorinated surfactants. Based on these findings, the synthesized surfactants may be environmentally friendly alternatives to PFOA and exhibit promising potential in industry applications.     

Bio-/Environment-Friendly Cationic Gemini Surfactant as Novel Corrosion Inhibitor for Mild Steel in 1 M HCl Solution

Bio-/environment-friendly cationic gemini surfactant, ethane-1,2-diyl bis(N,N-dimethyl-N-hexadecylammoniumacetoxy)dichloride, referred to as 16-E2-16, was synthesized and characterized. Corrosion inhibition effects of 16-E2-16 on mild steel (MS) surface in 1 M HCl solution at 30, 40, 50 and 60 °C were evaluated using gravimetric analysis, potentiodynamic polarisation and electrochemical impedance spectroscopy measurements. The nature of the protective inhibitor film formed on the MS surface was analysed by SEM, EDAX and FT-IR, while TGA was used to assure the thermal behaviour and stability of the film at high temperature. The formation of [inhibitor-Fe²⁺] on the surface of MS was confirmed by UV–visible spectroscopy. The inhibition efficiency of the studied inhibitor increased with increasing concentration and solution temperature. The compound behaved as a mixed type inhibitor and acted by blocking the electrode surface by means of adsorption obeying the Langmuir adsorption isotherm. Surface active properties and corrosion inhibition effects of 16-E2-16 in the presence of inorganic (NaI) and organic (NaSal) salts were also investigated and are discussed. Density functional theory calculations have been carried out to correlate the efficiency of the compound with its intrinsic molecular parameters.     

One Pot Synthesis and Properties of Cationic Surfactants: <Emphasis Type="Italic">n</Emphasis>-Alkyl-3-Methylpyridinium Bromide

Three new amphiphilic compounds i.e., n-decyl-3-methylpyridinium bromide (a), n-dodecyl-3-methylpyridinium bromide (b), and n-tetradecyl-3-methylpyridinium bromide (c), have been synthesized by condensation reaction and characterized by NMR (¹H, ¹³C) and FTIR spectroscopic techniques. The micellization behavior of the compounds has been studied in ethanol employing conductometry and UV/visible spectroscopy. The critical micellization concentration (CMC) values for compound a, b and c was found to be 0.31, 0.29 and 0.27 m mol L^?1, respectively. Effect of temperature on the CMC was checked in the range of 298-318 K. The thermodynamic parameters such as ΔG, ΔH and ΔS of the micellization process of these surfactants were computed. The negative values of ΔG and positive values of ΔH indicated the spontaneous and endothermic nature of the micellization process. Antimicrobial activities of these amphiphiles showed significant activity against different bacterial strains.     

Interactions Between a Sulfobetaine-Type Zwitterionic Gemini Surfactant and Fatty Acid Alkanolamide in Aqueous Micellar Solution

The critical micelle concentration (CMC) of 1,2-bis[N-methyl-N-(3-sulfopropyl)-alkylammonium]-ethane betaine (GCS12) was measured using a tensiometric method in the presence of inorganic salts. Inorganic salt has a little impact on the surface tension and CMC of zwitterionic gemini surfactant. The CMC value of GCS12 is 0.07 mmol/L in distilled water, while all CMC values are around 0.04–0.05 mmol/L in the presence of 0.5 % NaCl, 2 % NaCl, and 2 % NaCl + 0.05 % CaCl₂. The interactions between GCS12 and non-ionic surfactant lauric acid diethanolamide (CDA) were investigated by measuring the CMC of their mixtures at different molar ratios. CDA and GCS12 form mixed micelles and exhibit synergism when the mole fraction of CDA is higher than 0.25. Both the steric effect of the head group and GCS12 charge affect the formation and stability of the mixed micelles. Small amounts of GCS12 with a lower CMC penetrate into the micelle of nonionic surfactant with a higher CMC and reduce its degree of hydration inducing an attractive interaction between the two surfactants.     

Combined extracts of <Emphasis Type="Italic">Garcinia mangostana</Emphasis> fruit rind and <Emphasis Type="Italic">Cinnamomum tamala</Emphasis> leaf supplementation enhances muscle strength and endurance in resistance trained males

Background

A proprietary composition GMCT contains extracts of two popular Asian herbs viz., Garcinia mangostana (GM) fruit rind and Cinnamomum tamala (CT) leaf. We systematically evaluated physical performance and muscle strength enhancing ability of GMCT in a preclinical mouse model followed by a 42-days double-blind placebo controlled human trial in resistance trained adult males.

Methods

Four groups of Swiss albino mice (20–30 g body weight) (n?=?6) were fed a standard laboratory diet and given Carboxymethylcellulose sodium (CMC), 150 mg/kg GMCT (GMCT-150), 300 mg/kg GMCT (GMCT-300) or 50 mg/kg Oxymetholone (OXY) via oral gavage for 21 days. On day 22, the animals’ physical performance and muscle strength were assessed in a forced swimming test (FST) and forelimb grip strength experiment, respectively.In the human trial, thirty-eight resistance-trained young adults (mean age 26.32?±?4.39 years, body weight 67.79?±?12.84 kg, BMI 22.92?±?3.54 kg/m²) completed the trial. The participants received either GMCT (n?=?19; 800 mg daily) or matched placebo (n?=?19) for 42 days. As primary variables, 1-RM bench press, 1-RM leg press, and leg extension repetitions were measured at baseline and on days 14, 28 and 42 of the intervention. Anthropometric parameters and serum markers such as free testosterone, insulin-like growth factor 1 (IGF-1), insulin and lactate were also measured before and after the intervention.

Results

GMCT-300 mice showed significant improvement in swimming time (GMCT: 395.3?±?81.70 s vs. CMC: 271.6?±?56.86 s; p?=?0.0166), distance (GMCT: 341.22?±?65.88 m vs. CMC: 260.84?±?49.15 m; p?=?0.0461) and grip strength (GMCT: 43.92?±?6.97 N vs. CMC: 35.0?±?6.92 N; p?=?0.0490), compared with the CMC group.At the end of the 42-day human trial, the per protocol analyses reveal that mean changes from baseline 1-RM bench press (GMCT: 23.47?±?10.07 kg vs. PL: 3.42?±?2.06 kg; p?<?0.0001), leg press (GMCT: 29.32?±?16.17 kg vs. PL: 5.21?±?1.72 kg; p?<?0.0001), number of leg extension repetitions (GMCT: 6.58?±?2.57 vs. PL: 2.05?±?1.22; p?<?0.0001) in GMCT group were significantly improved, compared with placebo. Intergroup difference analyses show that the changes from baseline left arm (GMCT: 1.09?±?0.36 cm vs. PL: 0.68?±?0.42 cm; p?=?0.0023), right arm (GMCT: 1.50?±?0.44 cm vs. PL: 1.11?±?0.43 cm; p?=?0.0088) circumference and lean mass (GMCT: 2.29?±?2.09 kg vs. PL: 0.52?±?2.58 kg; p?=?0.0404) in GMCT group were also significantly improved, compared with placebo. In comparison to placebo, GMCT supplementation did not improve free testosterone, IGF-1, insulin or lactate levels. Parameters of clinical biochemistry, hematology, urine and vital signs of the participants were within the normal range.

Conclusion

GMCT supplementation is effective in increasing muscle strength, muscle size and, total lean mass, as well as endurance performance.Trial Registration.Clinical Trial Registry of India (CTRI/2015/01/005374), Registered on Jan 07, 2015; CTRI Website URL - http://ctri.nic.in

     

Counterion Effect on Krafft Temperature and Related Properties of Octadecyltrimethylammonium Bromide

In the present work, we have investigated the effect of some counterions on the Krafft temperature (T _K) and the micelle formation of octadecyltrimethylammonium bromide (OTAB) in aqueous solution. The results showed that the ions with more chaotropic nature increase the T _K while those with a kosmotropic, hydrotropic and less chaotropic nature lower the T _K of the surfactant. More chaotropic SCN^? and I^?, being weakly hydrated, form contact ion pairs with the octadecyltrimethylammonium ion and reduce the electrostatic repulsion between the surfactant molecules. As a result, these ions exhibit salting out behavior and raise the T _K of the surfactant. On the other hand, less chaotropic Cl^? and NO₃ ^?, kosmotropic SO₄ ^2? and F^? and hydrotropic benzoate and salicylate ions increase the solubility of the surfactant, with a consequent decrease in the T _K. SO₄ ^2?, F^?, benzoate and salicylate cannot form contact ion pairs with the weakly hydrated cationic part of OTAB. Rather, being extensively hydrated and kosmotropic in nature, these ions do not show any tendency to shed their hydrated water molecules to form contact ion pairs with the weakly hydrated octadecyltrimethylammonium ion and therefore, stay apart. As a result, the T _K of the surfactant decreases significantly in the presence of these ions. The critical micelle concentration (CMC) of the surfactant decreases significantly in the presence of these ions due to screening of the micelle surface charge by the added counterions. Consequently, the surfactant molecules attain better packing because of substantial reduction in the electrostatic repulsion between the charged head-groups, showing a significant decrease in the CMC.     

Synthesis and properties of fluorinated hydrophobic association polyacrylamide as thickener for hydraulic fracturing fluid

A novel, anionic fluorinated hydrophobic association polyacrylamide (FAPAM) was successfully synthesized from acrylamide (AM), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylic acid (AA), and 1H,1H,2H,2H-heptadecafluorodecyl acrylate (HFA) by radical micellar polymerization using sodium dodecyl sulfonate and potassium persulfate as a surfactant and an initiator, respectively. This synthesis was confirmed by Fourier transform infrared and nuclear magnetic resonance spectroscopy techniques. The results showed that the optimal content of the added HFA monomer was 0.3–0.5% in weight to the as-prepared FAPAM, which possessed 300–400 mg L^?1 of critical association concentration. The results also showed that the properties of FAPAM3-0.4 were best for the appropriate mass ratio of AM:AA:AMPS = 7:1:2. The apparent viscosity of FAPAM3-0.4 was 1350 mPa s in the aqueous solution, and the apparent viscosities of other samples were 161.5 and 148.3 mPa s when the Na⁺ and Ca²⁺ concentrations were 5000 and 2000 mg L^?1, respectively. Moreover, the FAPAM3-0.4 showed excellent temperature resistance and shearing resistance, in which the apparent viscosity was approximately 478.8 mPa s at 100 °C for 120 min. The viscosity could be completely restored or even it could be slightly higher than its original value when the shearing rate decreased. The results indicated that the excellent performance of FAPAM3-0.4 may make it a potential candidate as thickener for hydraulic fracturing fluid in oil and gas fields.     

Mixed Micellization Study of Alkyltrimethylammonium and Alkyltriphenylphosphonium Bromides in Aqueous Solution

Mixed micellization study of cationic surfactants viz. alkyltrimethylammonium bromides (C_nTAB) and alkyltriphenylphosphonium bromides (C_nTPPB) with similar hydrophobic groups (C₁₂-, C₁₄-, and C₁₆-) was performed using tensiometry and UV–visible light spectrophotometry techniques. Critical micelle concentration (CMC) values of the single and binary surfactant mixtures were obtained from a plot of surface tension versus the logarithm of surfactant concentration (C _s). The degree of synergy and various mixed micelle parameters like interaction parameter (β), activity coefficients (f ^m ) and interfacial parameters like surface pressure (π _CMC), packing parameter (P), surface excess concentration (Г _max), surface tension at the CMC (γ _CMC), and minimum area per molecule (A _min) were evaluated using the regular solution theory (RST). Thermodynamic parameters were calculated using several proposed models which suggest the mixed micellar system to be more thermodynamically stable than their respective individual components. In addition, a dye solubilization study was performed using a spectrophotometric method to validate the CMC data obtained from tensiometric method. Conductometric measurements were also carried out for the mixture of C₁₂TAB + C₁₂TPPB only as it showed a more negative β, indicating a higher degree of synergism.     

Effect of Sodium Carbonate on the Cloud Point in Alkyl Ether/Brine Systems: Apparent Relation with Dynamic Interfacial Tension Minimum

The effect of Na₂CO₃ on the cloud point in Na₂CO₃/surfactant/brine was investigated using two series of nonionic surfactants, C₁₃EO _x and C₁₇EO _x . The cloud point, T _cp, was found to decrease linearly with increasing Na₂CO₃ concentration. This was attributed to Na⁺ and particularly to CO₃ ^2?salting-out effect. The slope a = dTcp/d[Na₂CO₃] became more and more negative as the degree of ethoxylation is increased, suggesting that the higher the number of ethylene oxide (EO) groups the stronger is the cloud point depression for a given increment in Na⁺and CO₃ ^2?ions in solution. This was also illustrated by the linear variation of ΔT _cp = T _cp,0 ? T _cp,[Na2CO3] with the surfactant degree of ethoxylation.     

Studies on Solution Behavior of Aqueous Mixtures of Nonionic Polymer in Presence of Cationic Surfactants

The interactions of two gemini surfactants (16–s–16, s = 5, 6) and their conventional counterpart cetyltrimethylammonium bromide (CTAB) with polyethylene glycols (PEG 3000 and PEG 35000) have been investigated using conductivity, steady state fluorescence, viscosity and TEM techniques. The results indicate that there is no interaction between the PEG 3000/CTAB complex at lower polymer concentrations. However, a very weak interaction is observed at higher concentrations (0.5 and 1.0 wt% PEG 3000), while PEG 3000 and PEG 35000 interact with the gemini surfactants. Both critical aggregation concentration (CAC) and critical micelle concentration (CMC) increases with polymer concentration but are independent of the polymer molecular weight. From steady state fluorescence it is found that the addition of PEG results in no drastic decrease in the aggregation number (N) for all surfactants. This suggests that the atmosphere surrounding the polyion-bound micelles, with respect to the influence on the forces acting at the micelle surface, is equivalent to the counterion/water atmosphere surrounding free micelles. The relative viscosity (η _r) results show an enhancement in η _r for all the surfactants. The increase in η _r is quite significant with gemini surfactants. Polymer-surfactant interaction also depends on the polymer molecular weight. Also, the interaction seems to affect both inter polymer–polymer association as well as chain expansion. Additionally the surfactant induced changes in the polymer conformation depicted by TEM study at the micro structural level confirmed previously observed interactions determined by different analytical techniques.     

Preparation of high surface area mesoporous nickel oxides and catalytic oxidation of toluene and formaldehyde

Mesoporous nickel oxide (NiO) nanoparticles were synthesized by the thermal decomposition reaction of Ni(NO₃)₂·9H₂O using oxalic acid dihydrate as the mesoporous template reagent. The pore structure of nanocrystals could be controlled by the precursor to oxalic acid dihydrate molar ratio, thermal decomposition temperature and thermal decomposition time. The structural characteristic and textural properties of resultant nickel oxide nanocrytals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N₂ adsorption–desorption isotherm and temperature programmed reduction. The results showed that the most excellently mesoporous nickel oxide particles (m-Ni-1-4) with developed wormlike pores were prepared under the conditions of the mixed equimolar precursor and oxalic acid and calcined for 4 h at 400 °C. The specific surface area and pore volume of m-Ni-1-4 are 236 m² g^?1 and 0.42 cm³ g^?1, respectively. Over m-Ni-1-4 at space velocity = 20,000 mL g^?1 h^?1, the conversions of toluene and formaldehyde achieved 90 % at 242 and 160 °C, respectively. It is concluded that the reactant thermal decomposition with oxalic acid assist is a key step to improve the mesoporous quality of the nickel oxide materials, the developed mesoporous architecture, high surface area, low temperature reducibility and coexistence of multiple oxidation state nickel species for the excellent catalytic performance of m-Ni-1-4.