Effect of polyoxypropylene chain length on the critical micelle concentration of propylene oxide-ethylene oxide block copolymers

In this work, the surface activity of block copolymer nonionic surfactants (RPE) has been determined, i.e., critical micelle concentration (CMC), surface excess concentration (Γ), surface area demand per molecule (A), surface tension at CMC (γCMC). A linear decrease of ln[CMC] vs number of oxypropylene units in copolymer molecule was observed. The change in the work of cohesion per oxypropylene group when passing from molecular into micellar state, calculated from the Shinoda equation, was 0.43kT for the studied compounds.

Correlation of Critical Micelle Concentration of Sodium Alkyl Benzenesulfonates with MolecularDescriptors

The hydrophobic-hydrophilic segment geometries of 36 sodium alkyl benzenesulfonates were fully optimized and calculated by abinitio RHF/6-31G（d）, quantum chemical data such as the charge density, the energy of molecular orbital and the dipole moment were obtained. Based on two topological descriptors and one quantum chemical descriptor, a significant quantitative structure-property relationship （QSPR） model for the critical micelle concentration （Cmc） of sodium alkyl benzenesulfonate surfactants was obtained by using the multiple linear regression technique. The good correlation coefficient of Re （0. 980） and cross-validation correlation coefficient Rcv^2 （0. 974） indicate the excellent capability and stability of the regression equation developed. In addition, linear relationships between logarithm of Cmc and the dipole moment of surfaetant hydrophobic hydrophilic segments for each homologous series have also been established with high correlation coefficient.

A Method for Determination of Critical Micellar Concentration of Surfactant

Measure the chemiluminescence value of acridine compound as luminescent agent in the surfactant solution with a series of concentrations,according to the value of the obtained luminescent value and the value of the corresponding surfactant concentration in the surfactant solution,linear fitting is carried out to obtain several fitting lines,and the minimum value of the surfactant concentration corresponding to the intersection of the two adjacent fitting lines is the critical micelle concentration of the surfactant.According to the results,the critical micelle concentration of Dodecyl trimethyl ammonium chloride is 11.5 mmol/L,Hexadecyl trimethyl ammonium Bromide is 0.357 mmol/L,Sodium dodecyl sulfate is 7.64 mmol/L,sodium N-lauroylsarcosinate is 0.890 mmol/L,Triton X-100 is 0.309 mmol/L,3-((3-Cholamidopropyl)dimethylammonium)-1-propanesulfonate is 9.53 mmol/L,3-(N,N-dimethyldodecylammonio)propanesulfonate is 1.73 mmol/L.The results were similar to those obtained by traditional methods,the method can be used in the study of critical micelle concentration of surfactants.

Long-lasting chemiluminescence by aggregation-induced emission surfactant with ultralow critical micelle concentration

The development of green and simple chemiluminescence(CL)systems with intensive and long-lasting emission is highly desirable in lighting and extension of their applications.In this study,it is found that the involvement of aggregation-induced emission(AIE)surfactant could greatly enhance the CL of luminol–H2O2–Co2+system.The inserted hydrophobic tetraphenylethylene fluorophore in AIE is able to increase the hydrophobicity of alkyl chain and decrease the critical micelle concentration(CMC)of surfactant.The synergistic effect of micelle-improved enrichment and CL resonance energy transfer endows luminol–H2O2–Co2+system intensive and long-lasting emission under neutral pH conditions(pH 7.4).The visible emission is still observed even after 60 min.Our study has opened a new avenue for exploring green and simple effective CL systems through AIE surfactant with unltralow CMC toward various applications in lighting,optical sensing,and photocatalysis,etc.

Physico-chemical parameters for the assembly of moxifloxacin hydrochloride and cetyltrimethylammonium chloride mixture in aqueous and alcoholic media

The aggregation behavior of the mixture of cetyltrimethylammonium chloride(CTAC), a cationic surfactant, and moxifloxacin hydrochloride(MFH), a fourth-generation fluoroquinolone antibiotic drug, has been studied using the conductivity technique in aqueous and alcoholic(EtOH, 1-PrOH, and 2-BuOH)media. The study was performed at several temperatures between 298.15 and 323.15 K at 5 K intervals.The assembly has been characterized by evaluating the micellar parameters, such as the critical micelle concentration(CMC) and the counter ion binding(β), of the CTAC + MFH mixture. The values of the CMC for the assembly of the CTAC + MFH mixture were reliant on the composition of alcohols in the mixed solvents and the temperature. The CMC values of the CTAC + MFH mixture increased with increasing temperature;that is, assembly was delayed by increased temperature. The micellization of the CTAC + MFH mixed system was delayed in alcoholic media. The observed-ΔG0mvalues for the association of the CTAC + MFH mixed system demonstrated a spontaneous aggregation process under all study conditions.Based on the-ΔH^(0)_(m) and +ΔS^(0)_(m) values, the association of the CTAC + MFH mixture is exothermic and the interaction forces acting between the CTAC and MFH species are hydrophobic, ion–dipole, and electrostatic interactions. The transfer properties and enthalpy–entropy compensation were also assessed and described comprehensively.

Adsorption of Natural Surfactant on Sandstone in Enhanced Oil Recovery: Isotherms and Kinetics Studies

In chemical enhanced oil recovery, surfactants are injected into the reservoir with the intention to lower interfacial tension (IFT) between the water and oil phases, and thereby bring about efficient displacement of oil. However, the adsorption of the surfactants to reservoir rock surfaces leads to the loss and reduction in concentration of the surfactants, which in turn reduces the overall efficiency of the oil recovery process, with attendant financial losses. In this work, the adsorption of Quillaja Saponaria (QS), a novel, natural, non-ionic surfactant, on crushed sandstone reservoir rock is investigated. X-ray diffraction (XRD) study of clean sandstone particles has been undertaken to determine the main components present in the sand particles. The conductivity method was used to measure CMC and the surfactant concentrations in aqueous solutions. Batch adsorption experiments were used to determine the amount of QS adsorbed on rock surface. Equilibrium conditions were reached after almost 5 days. From the results of the study, the Langmuir isotherm model is more suited for predicting the adsorption behaviour of QS on sandstone. The kinetic adsorption of QS obeys the pseudo-second order model. This study is particularly relevant in surfactant selection for chemical EOR processes.

Prediction on Critical Micelle Concentration of Nonionic Surfactants in Aqueous Solution:Quantitative Structure-Property Relationship Approach

In order to predict the critical micelle concentration (cmc) of nonionic surfactants in aqueous solution,a quantitative structure-property relationship (QSPR) was found for 77 nonionic surfactants belonging to eight series. The best-regressed model contained four quantum-chemical descriptors,the heat of formation (ΔH),the molecular dipole moment (D),the energy of the lowest unoccupied molecular orbital (E_ LUMO ) and the energy of the highest occupied molecular orbital (E_ HOMO ) of the surfactant molecule; two constitutional descriptors,the molecular weight of surfactant (M) and the number of oxygen and nitrogen atoms (n_ ON ) of the hydrophilic fragment of surfactant molecule; and one topological descriptor,the Kier & Hall index of zero order (KH0) of the hydrophobic fragment of the surfactant. The established general QSPR between lg(cmc) and the descriptors produced a relevant coefficient of multiple determination:R 2=0.986. When cross terms were considered,the corresponding best model contained five descriptors E_ LUMO ,D,KH0,M and a cross term n_ ON ·KH0,which also produced the same coefficient as the seven-parameter model.

Intermolecular Interactions in Self-Assembly Process of Sodium Dodecyl Sulfate by Vertically Polarized Raman Spectra

Molecular self-assembly is extremely important in many fields, but the characterization of their corresponding intermolecular interactions is still lacking. The C-H stretching Raman band can reflect the hydrophobic interactions during the self-assembly process of sodium dodecyl sulfate （SDS） in aqueous solutions. However, the Raman spectra in this region are seriously overlapped by the OH stretching band of water. In this work, vertically polarized Raman spectra were used to improve the detection sensitivity of spectra of C-H region for the first time. The spectral results showed that the first critical micelle concentration and the second critical micelle concentration of SDS in water were 8.5 and 69 mmol/L, respectively, which were consistent with the results given by surface tension measurements. Because of the high sensitivity of vertically polarized Raman spectra, the critical micelle concentration of SDS in a relatively high concentration of salt solution could be obtained in our experiment. The two critical concentrations of SDS in 100 mmol/L NaCl solution were recorded to be 1.8 and 16.5 mmol/L, respectively. Through comparing the spectra and surface tension of SDS in water and in NaCl solution, the self-assembly process in bulk phase and at interface were discussed. The interactions among salt ions, SDS and water molecules were also analyzed. These results demonstrated the vertically polarized Raman spectra could be employed to study the self-assembly process of SDS in water.

Synthesis and Surface Activity of Novel Triazole-based Cationic Gemini Surfactants

The synthesis and surfactant activities of two new cationic gemini surfactants containing triazole compound as spacer were described. Their critical micelle concentrations (CMC), which are 1.8×10-4 mol/L and 3.9×10-4 mol/L respectively, are much lower than that of conventional surfactant cetyltrimethyl ammonium chloride (CTAC). In addition, compared with some gemini surfactants containing phenylene, xylylene and stilbenyl as spacer, this new kind of surfactants has good solubility in water at room temperature because of containing more hydrophilic groups or atoms in molecules.

Functional characterization of a biosurfactant-producing thermo-tolerant bacteria isolated from an oil reservoir

A Bacillus subtilis strain JA-1 isolated from an oil reservoir was studied. This strain is capable of growth and producing biosurfactant at a temperature of 60 ℃. In nutrient medium it produced biosurfactant which reduced the surface tension from 68.2 mN/m to 28.3 mN/m, with the critical micelle concentration （CMC） of 48 mg/L. The measured surface tension indicated that the biosurfactant possessed stable surface activity at high temperature and a specific range of pH and salt concentrations. The results of thin layer chromatography （TLC） together with FT-IR showed that the metabolic product of strain JA-1 is a lipopeptide biosurfactant. The ability to growth at high temperature and to produce biosurfactant makes strain JA-1 promising for enhanced oil recovery.

Influence of Structural Variations on Electrical Conductivity and Solubility of 1-Vinyl-3-alkylimidazole Halogen Ionic Liquids

Several 1-vinyl-3-alkylimidazolium halogens [VRIM]X, which are functional materials with ethylenic bonds, were synthesized using the microwave-assisted synthesis method. Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy were carded out to analyze the resultant structures. The electrochemical properties and solubility of [VRIM]Br were investigated and discussed in detail. The temperature dependence of pure [VRIM]Br over a wide temperature range of 298.15-323.15 K fitted the Arrhanius equation well. At certain low concentrations, the electrical conductivity of the [VRIM]Br solution significantly increased with increasing solution concentration. The electrical conductivities of the [VRIM]Br observed in water, methanol, and ethanol showed the trend σwater〉 σmethanol 〉σethanol Conductometry showed that the critical miceUe concentrations of the bromines in water, methanol, and ethanol were 6.8-6.9 × 10-6, 1.4-1.5 × 10-5, and 1.9-2.0×10-5 mol.L-1, respectively; these results indicate that [VRIM]Br is an excellent surfactant. The solubility of [VRIM]X in common solvents was determined at 293.15 K, and results indicated that a decrease in solubility could be observed with decreasing dielectric constant of the solvent, elongation of the alkyl chain of the cation, and increasing anion size. Solubility parameters were also determined according to the Hildebrand-Scoff equation.

Synthesis and surface activity of a novel heterodouble chained N-acyltaurate amphiphile

A novel double chained amphiphile, N-(α-4-hexylphenoxy)-lauroyltaurate (abbreviated as 10 + 6B-T), has been synthesized. The structures of main intermediate products and the title product were characterized by 1H NMR. The new amphiphile shows high surface activity. The critical micelle concentration (cmc), which is 1.1 × 10?5 mol/L, is much lower than that of conventional double chained surfactants, such as sodium bis(2-ethylhexyl)sulfosuccinate (AOT).

Effect of surfactant type on interfacial area and liquid mass transfer for CO_2 absorption in a bubble column

The effect of different surfactants(n-octyltrimethylammonium bromide(OTABr),sodium dodecyl benzene sulfonate(SDBS) and Tween 80) with different critical micelle concentrations(CMC) on the CO_2 absorption into aqueous solutions in a bubble column is analyzed in the present work.The presence of these surfactants increased the gas-liquid interfacial area,and decreased the liquid phase mass transfer coefficient,but with significant different extent.The results indicated that the CMC can be a key parameter affecting the mass transfer of CO_2 absorption into a dilute aqueous solution of a surfactant.Sardeing's model was used to fit the experimental data successfully by re-correlating the parameters.

EFFECT OF ANIONIC SURFACTANT UPON THE VISCOSITY OF POLYMER GUAR GUM SOLUTIONS

The reduced viscosity of polymer guar gum solutions containing a certain concentration of sodium dodecyl benzene sulfonate （SDBS） was measured. It has been found that the Huggins coefficient kH of polymer solutions is very sensitive to the concentration of the surfactant, CSDBS, in solutions. If CSDBS is lower than CMC, the critical micelle concentration of SDBS, kH increases rapidly with CSDBS. On the other hand, if CSDBS is larger than CMC, kH decreases rapidly with CSDBS. Comparatively, the intrinsic viscosity of polymer solution does not show a notable change with CSDBS. The experimental results indicate that the interchain association of polymer guar gum in solution is greatly associated with SDBS interacted with polymer chains through hydrogen bonds. However, the effect of SDBS upon the intrachain association of polymer guar gum solution is negligible, presumably due to the fact that guar gum is a slightly stiffened random-coil chain polymer.

Synthesis and characterization of a novel amphiphilic biodegradable β-cyclodextrin/poly(γ-benzyl L-glutamate) copolymer

β-Cyclodextrin/poly（γ-benzyl L-glutamate） （β-CD-PBLG） copolymers were synthesized by ring-opening polymerization of N- carboxy-γ-benzyl L-glutamate anhydride （BLG-NCA） in N,N-dimethylformamide （DMF） initiated by mono-amino-β-cyclodextrin（H2N-β-CD）. The structures of the copolymers were confirmed by IR, ^1H NMR and GPC. The fluorescence technique was used to determine the critical micelle concentrations （CMC） of copolymer micell solution, the diameter and the distribution of micelles were characterized by DLS. The results showed that BLG-NCA could be initiated by H2N-β-CD to produce copolymer. The nanomicells were formed by these copolymers in water.

Emulsion Polymerization of Vinyl Acetate in the Presence of a New Cationic Surfactant

In this study, the emulsion homopolymerization system containing vinyl acetate, potassium persulfate, a new cationic polymeric surfactant and water was studied by the applying semi-continuous emulsion polymerization process. The effects of new polymeric emulsifier on the physicochemical properties of obtained vinyl acetate latexes were investigated depending on vinyl acetate percentage in the polymerization recipe, and two thermal initiators in homopolymerization.

Surface Performance Testing of Cardanol Polyoxyethylene Ether and Its Application in Detergent

Cardanol polyoxyethylene ether is a kind of nonionic surfactants based on natural raw materials, with good surface activity and resistance to hard water. At 25 ℃, the value of critical micelle concentration （CMC） is 6.09×10-6 mol/L, and the lowest surface tension （TcMc） is 38.08 mN/m. Moreover, cardanol polyoxyethylene ether has strong salt tolerance to monovalent inorganic salts; with the increase of concentration of divalent inorganic salt, the surface activity of cardanol polyoxyethylene ether is enhanced. The effect of monohydric alcohol on the surface activity of cardanol polyoxyethylene ether is complex： the ability of BGF-10 to form micelles increases and then decreases with the increase of the concentration of monohydric alcohol, cardanol polyoxyethylene ether has a synergistic effect with anionic, nonionic and cationic surfactants, especially with hexadecyltrimethylammonium bromide （CTAB）, and its critical micelle concentration is decreased by 2.52%, while the surface tension is decreased by 11.49%. Test results also show, comparing to nonylphenol polyoxyethylene ether, the emulsifying and the thickening performances of cardanol polyoxyethylene ether are better, and its foam performance is lower. Also, the cloud point of cardanol polyoxyethylene ether is higher than nonylphenol polyoxyethylene ether. In most case, the detergency of cardanol polyoxyethylene ether is better than or equivalent to nonylphenol polyoxyethylene ether. cardanol polyoxyethylene ether is an excellent alternative to nonylphenol polyoxyethylene ether in detergents.

Accurate and sensitive probing of onset of micellization based on absolute aggregation-caused quenching effect

Probing the onset of micellization,or determining the critical micelle concentration(CMC),is of crucial importance while remains to be challenged by growing demand for extraordinary sensitivity and accuracy.Although fluorometry has attracted wide attention owing to its superiority in simplicity and sensitivity over other methods,the presence and fluctuation of background fluorescence of conventional fluorescent probes undermine the accuracy of CMC determination.Herein,a series of novel fluorescent probes without background fluorescence at a concentration below CMC owing to absolute aggregation-caused quenching(aACQ)are utilized for sensitive and accurate measurement of CMC.The aACQ probes aggregate spontaneously and instantly in an aqueous environment owing to molecular π-π stacking with fluorescence quenching absolutely.Therefore,the absence of background fluorescence at a concentration below CMC clears relevant interference associated with conventional fluorophores.In this study,the new method is applied for versatile surfactants with CMCs ranging from nanomolar to millimolar concentrations,especially copolymers with ultralow CMC.The higher sensitivity and accuracy are highlighted by comparison with conventional probes.

Hydrophobic terminal group of surfactant initiating micellization as revealed by^1H NMR spectroscopy

The critical aggregation concentration（CAC） of four with three kinds of conventional surfactants, namely,two cationic surfactants [hexadecyltrimethyl ammonium bromide（CTAB） and tetradecyltrimethyl ammonium bromide（TTAB）], one anionic surfactant [sodium dodecyl sulfate（SDS）], and a nonionic surfactant [Triton X-100（TX-100）], were determined by variation of ^1H chemical shifts with surfactant concentrations. Results show that the CAC values of protons at different positions of the same molecule are different, and those of the terminal methyl protons are the lowest, respectively, which suggests that the terminal groups of the alkyl chains aggregates first during micellization. Measurement of the transverse relaxation time（T2） of different protons in SDS also show that the terminal methyl protons start to decrease with the increase in concentration first, which supports the above mentioned tendency.

Near-Infrared Hydrophobic Probes as Molecular Light Switch for CMC Determination of Triton X-100 Solution

The fluorescence behavior of two near-infrared (NIR) chromophores with linear alkyl chains of different lengths, 2-[4'chloro-7'(3'ethyl-2'benzothiazolinylidene)-3',5'-(1''',3'''-propanediyl)-1',3',5'-heptantriene-1'-yl]-3-ethylbenzo- thiazolium iodide (Probe I) and 2-[4'chloro-7'(3'hexadecyl-2'benzothiazolinylidene)-3',5'-(1''',3'''-propanediyl)- 1',3',5'-heptantriene-1'-yl]-3-ethylbenzothiazolium iodide (Probe II), in aqueous solution containing different con-centrations of surfactants was studied. The fluorescence of the probe with a short chain (probe I) was completely quenched in water and aqueous solution containing a low concentration (below the critical micelle concentration, CMC) of surfactant Triton X-100. However, the fluorescence reappeared and reached maximum rapidly once the concentration of the surfactant approached the CMC. The probe with a long chain (probe II) displayed a similar fluorescence behavior but more dramatically fluorescent recovery in Triton X-100 system, which gave a direct in-dication for the micelle forming process and provided a simple method for the determination of the critical micelle concentration of the surfactant. The CMC values determined by this method were in good agreement with those ob-tained by other techniques. The fluorescence behavior of the two probes in other surfactant systems was also inves-tigated.