Counterion Binding Constant Research Articles

음이온성 계면활성제(DBS)와 비이온성 계면활성제(Brij 30과 Brij 35)와의 혼합미셀화에 대한 비교연구

ABSTRACT. The critical micelle concentration (CMC) and the counter ion binding constant (B) for the mixe dmicellizations of DBS (sodium dodecylbenzenesulfonate) with Brij 30 (polyoxyethylene(4) lauryl ether) and Brij 35 (polyoxyethylene(23) lauryl ehter) at 25 o C in pure water and in aqueous solutions of n-butanol were determined as a function of α 1 (the overall mole fraction of DBS) by the use of electric conductivity method. Various thermodynamic parameters (X i , γ i , C i , a iM , β, and △H mix ) were calculated and compared for each mixed surfactant system by means of the equations derived from the nonideal mixed micellar model. The results show that the molecules of DBS interact more strongly with Brij 35 than Brij 30 and that the DBS/Brij 35 mixed system has greater negative deviation from the ideal mixed micellar model than the DBS/Brij 30 mixed system. Keywords: DBS, Brij 35, Brij 30, Critical micelle concentration, Counter ion binding constant, Non ideal mixe dmicellar model

순수 물에서 CPC/Brij 35 혼합계면활성제의 미셀화에 대한 연구

The values of critical micelle concentration (CMC) and counter ion binding constants (B) in a micellar state of CPC (1-hexadecylpyridinium chloride) with Brij 35 (polyoxyethylene(23) lauryl ether) in water were determined as a function of (the overall mole fraction of CPC) by the use of electric conductivity method. Various thermodynamic parameters () were calculated and analyzed by means of the equations derived from the non-ideal mixed micellar model. And thermodynamic parameters () for the micellization of CPC/Brij 35 mixtures were also calculated from the temperature dependence of the CMC values. The values of are all negative, but the values of and are positive or negative, depending on the measured temperature and .

전도도법에 의한 DPC/Brij 35 혼합계면활성제의 미셀화에 대한 연구

The values of critical micelle concentration (CMC) and counter ion binding constants (B) in a micellar state of DPC (1-dodecylpyridinium chloride) with Brij 35 (polyoxyethylene(23) lauryl ether) at 298K in water were determined as a function of α (the overall mole fraction of DPC) by the use of electric conductivity method and surface tension method. Various thermodynamic parameters (X , α , C , a , β, and △ H ) were calculated by means of the equa- tions derived from the nonideal mixed micellar model. The results show that the activities of DPC in a micellar state have great negative deviations and those of Brij 35 have great positive deviations from the ideal mixed micellar model. Various thermodynamic parameters ( △ G , △ H , and △ S ) for the micellization of DPC/Brij 35 mixtures were cal- culated also from the temperature dependence of the CMC values. The values of △ G are all negative, but the values of △ S and △ H are all positive or negative, depending on the measured temperature and α .

Aggregation and adsorption properties of sodium dodecyl sulfate in water–acetamide mixtures

The critical micelle concentration (cmc) of sodium dodecyl sulfate was determined in water + acetamide media from 0 to 70 wt% of acetamide and at temperatures in the range from 20 to 40 °C by using conductance, surface tension, and fluorescence methods. The cmc increases with increase in acetamide concentration and the reported [M.S. Akhter, Colloids Surf. A 121 (1997) 103] decrease in cmc was not observed. The limiting surface tension at the cmc does not have any dependence on the amount of acetamide added. The cmc data as a function of temperature were used to estimate the free energy, enthalpy, and entropy terms for micellization. Enthalpy–entropy compensation takes place during micellization. Counterion binding constant, surface excess, and aggregation number of SDS decrease with increasing acetamide concentration and become almost constant for weight percentages of acetamide greater or equal to 30. Pyrene appears to move from the interior of the SDS micelle to the micellar interface at about 30 wt% acetamide. The empirical relations reported by Aguiar et al. [J. Aguiar, P. Carpena, J.A. Molina-Bolivar, C. Carnero Ruiz, J. Colloid Interface Sci. 258 (2003) 116] between the parameters of a sigmoid-type expression for the ratio of fluorescence emission intensities of pyrene and surfactant properties are found to be applicable to SDS in water + acetamide medium below 20 wt% acetamide only. Standard free energy of micellization has linear correlations with reciprocal of dielectric constant and Gordon parameter of the solvent. The water + acetamide medium behaves similar to mixed solvents containing water and any polar liquid nonaqueous solvent and this study highlights the significance of solvophobicity.

Phase behavior and size variation of AOT-based W/O microemulsions by substituting H + for Na + as the counterion

The purpose of this study is to investigate how the difference in screening of electrostatic repulsions between polar headgroups by counterions affects the phase behavior and size of AOT-based W/O microemulsions. Na-AOT and H-AOT were used as the surfactants. The counterion binding constants determined by the relationship between the CMC and the counterion concentration indicate that the screening effect of H + is weaker than that of Na +. A mixture of water/Na-AOT and/or H-AOT/isooctane was emulsified by changing the mixing ratio of H-AOT, X H-AOT = 0–1, keeping the water content ( w 0 = [ water ] / [ surfactant ] ) = 10 and the total AOT − concentration = 0.1 M. FT-IR and DLS measurements were carried out for the upper content of the emulsified mixture to investigate phase behavior and size variation. It was found that the phase behavior can be divided into three regions: (1) the W/O microemulsion region at 0 ≤ X H-AOT ≤ 0.52, (2) the phase transition region at 0.52 < X H-AOT < 0.7, and (3) the phase separation region at 0.7 ≤ X H-AOT ≤ 1. In region (1), the size of the W/O microemulsions increases from 8 to 110 nm, although the amounts of water and surfactant in the W/O microemulsions are constant. In region (2), the amounts of water and surfactant decrease to form the lower phase, whereas the upper phase still contains the W/O microemulsions and the size decreases from 110 to 15 nm with increasing X H-AOT. In region (3), the mixture separates into two phases. The possible causes of the phase behavior and the size variation were discussed by focusing on the FT-IR spectra of symmetric sulfonate stretching vibration band due to the polar headgroup of AOT −.

TTAB/Brij 35 혼합계면활성제의 미셀화에 미치는 부탄올 이성질체들의 효과

순수 물 및 부탄올 이성질체의 수용액에서 양이온 계면활성제인 trimethyltetradecylammonium bromide(TTAB)와 비이온 계면활성제인 polyoxyethylene(23) lauryl ether(Brij 35)로 이루어진 혼합계면활성제의 임계미셀농도(CMC)와 반대이온의 결합상수값(B)을 TTAB의 겉보기 몰분율(1)의 함수로서 전도도법과 표면장력계법으로 측정하였다. 이와 같이 측정한 CMC 값에 비이상적 혼합미셀화 모델을 적용함으로써 여러 가지 열역학적 함수값(Xi, i, Ci, aiM, 및 △Hmix)들을 계산하고 분석하였다. TTAB/Brij 35 혼합계면활성제의 미셀화에 미치는 부탄올 이성질체의 효과는 n-부탄올>iso-부탄올>tert-부탄올>물 크기순으로 나타났다. critical micelle concentration (CMC) and the counter ion binding constant (B) in a mixed micellar state of the trimethyltetradecylammonium bromide (TTAB) with the polyoxyethylene (23) lauryl ether (Brij 35) at 25oC in water and in aqueous solutions of butanol isomers were determined as a function of 1 (the overall mole fraction of TTAB) by the use of electric conductivity method and surface tensiometer method. Various thermodynamic parameters (Xi, i, Ci, aiM, and Hmix) were calculated by means of the equations derived from the nonideal mixed micellar model. The results say that the effects of butanol isomers on the micellization of TTAB/Brij 35 mixtures have been in the order of n-butanol>iso-butanol>t-butanol> water.

Micellization Behaviour of AOT in the Presence of Sodium Citrate

Abstract Critical micelle concentration (cmc) values of dioctyl sulfosuccinate (AOT) in aqueous trisodium citrate (NaCit) solution were determined as functions of electrolyte concentration and temperature by using surface tension and EMF methods. Values of surface excess, counter ion binding constant (β), surface area, and standard free energies of micellization and adsorption of AOT were evaluated. Using fluorescence-quenching method, aggregation number and polarity index of AOT were also determined. A sudden increase in the value of β from almost 0.4 to 0.8, associated with a sudden increase in the aggregation number and decrease in the polarity index, was observed with a NaCit concentration of about 0.007 mol kg−1, which is considered to be due to change in the micellar shape of AOT. The present study confirms the special counter ion binding behaviour of AOT as an additional special feature of AOT.

TTAB/Brij 35 혼합계면활성제의 미셀화에 대한 열역학적 연구

양이온 계면활성제인 Tetradecyltrimethylammonium bromide(TTAB)와 비이온 계면활성제인 Polyoxyethylene(23) lauryl ether(Brij 35)로 구성된 혼합계면활성제의 임계미셀농도(CMC)와 반대이온의 결합상수(B) 값을 α1 (TTAB의 겉보기 몰분율)의 함수로서 15 oC에서 35 oC까지 전도도법과 표면장력계법으로 측정하였다. CMC와 B 값의 온도에 따른 변화로부터 TTAB/Brij 35 혼합계면활성제의 미셀화에 대한 여러 가지 열역학 함수(ΔGom, ΔHom, 및 ΔSom) 값들을 계산하고 분석하였다. 계산한 ΔGom 값은 측정한 온도범위 내에서 모두 음의 값을 나타내었다. 그러나 ΔHom와 ΔSom 값은 측정한 온도와 α1의 값에 따라 양 혹은 음의 값을 나타내었다. The critical micelle concentrations (CMC) and the counter ion binding constants (B) in a micellar state of the mixed surfactant systems of Tetradecyltrimethylammonium bromide (TTAB) with Polyoxyethylene(23) lauryl ether (Brij 35) in water were determined as a function of α1 (the overall mole fraction of TTAB) by the use of electric conductivity method and surface tensiometer method from 15 oC to 35 oC. Values of thermodynamic parameters (ΔGom, ΔHom, and ΔSom) for the micellization of TTAB/Brij 35 mixtures were calculated and analyzed from the temperature dependence of CMC values. The results say that the measured values of ΔGom are all negative at the whole measured condition but the values of ΔSom and ΔHom are positive or negative, depending on the measured temperature and α1.

Micellization behaviour of sodium dodecyl sulfate in different electrolyte media

Critical micelle concentrations (cmc) of sodium dodecyl sulfate (SDS) in the presence of sodium chloride, sodium acetate, sodium propionate and sodium butyrate were measured by surface tension (at 20, 25 and 30 °C), conductance (at 25 °C) and EMF (at 25 °C) methods. Values of surface excess, counter ion binding constant, surface area, and standard free energies of micellization and adsorption of SDS in the presence of these electrolytes were also determined. The co-ions are found to have no effect on the cmc of SDS contrary to the report made earlier, but have an influence on its surface activity behaviour. Aggregation numbers were measured by using the steady-state fluorescence quenching method, whereas surface potentials were computed by solving the non-linearized Poission–Boltzmann equation. With added electrolyte aggregation number of SDS increases whereas its surface potential decreases. Butyrate co-ion affects the aggregation number of SDS when its concentration is ≥0.035 mol kg −1. This work has addressed the effect of co-ion on the adsorption and micellization parameters of SDS and the results have utility in designing formulations consisting of ionic surfactants and electrolytes for various applications.

DBS/Brij 35 혼합계면활성제의 미셀화에 미치는 n-부탄올 효과

순수 물 및 n-부탄올 수용액(0.1M, 0.2M, 0.3M)에서 음이온 계면활성제인 sodium dodecyl benzenesulfonate(DBS)와 비이온 계면활성제인 dodecyl polyoxyethylene(23) lauryl ether(Brij 35)의 혼합계면활성제의 임계미셀농도(CMC)와 반대이온의 결합상수값(B)을 DBS의 겉보기 몰분율(1)의 함수로서 전도도법과 표면장력계법으로 측정하였다. 이와 같이 측정한 CMC값에 비이상적 혼합미셀화모델을 적용함으로써 여러 가지 열역학적 함수값(Xi, i, Ci, aiM, 및 Hmix)들을 계산하고 분석하였다. 그리고 DBS/Brij 35 혼합계면활성제의 미셀화에 미치는 n-부탄올의 농도에 따른 열역학 함수값들의 변화를 측정하고 분석하였다. The critical micelle concentration (CMC) and the counterion binding constant (B) in a mixed micellar state of the sodium dodecylbenzenesulfonate (DBS) with the polyoxyethylene(23) lauryl ether (Brij 35) at 25oC in water and aqueous solutions of n-butanol (0.1M, 0.2M, and 0.3M) were determined as a function of a1 (the overall mole fraction of DBS) by the use of electric conductivity method and surface tensiometer method. Various thermodynamic parameters (Xi, i, Ci, aiM, , and Hmix) were calculated by means of the equations derived from the nonideal mixed micellar model. The effect of n-butanol on the micellization of the DBS/Brij 35 mixtures has been also studied by analyzing the measured and calculated thermodynamic parameters.

DBS/Brij 30 혼합계면활성제의 미셀화에 대한 열역학적 연구

The critical micelle concentrations (CMC) and the counter ion binding constants (B) in a micellar state of the mixed surfactant systems of sodium dodecylbenzenesulfonate (DBS) with polyoxyethylene(4) lauryl ether (Brij 30) in water were determined as a function of 1 (the overall mole fraction of DBS) by the use of electric conductivity method and surface tensiometer method from 288 K to 308 K. Various thermodynamic parameters (Smo, Hmo, and Gmo) for the micellization of DBS/Brij 30 mixtures were calculated and analyzed from the temperature dependence of CMC values. The measured values of Gomare all negative but the values of Smo are positive in the whole measured temperature region. On the other hand, the values of Hmo are positive or negative, depending on the measured temperature and 1.

Micellization Behaviour of Sodium Dodecylsulfate and Dioctyl Sulfosuccinate in the presence of Sodium Salicylate

Critical micelle concentrations of sodium dodecylsulfate (SDS) and dioctyl sulfosuccinate (AOT) were determined at 25 °C in aqueous medium as a function of sodium salicylate (NaSa) concentration by surface tension and EMF methods. In the case of SDS, conductance method was also used. Salicylate ion is found to affect the critical micelle concentrations of SDS and AOT when the concentration of NaSa becomes > 0.03 and 0.02 mol kg -1 , respectively. In the presence of NaSa, the counter ion binding constant for AOT has a single value equal to 0.47 and that for SDS is equal to 0.56. The higher value of the counter ion binding constant equal to about 0.8 observed earlier for AOT in sodium chloride, sodium acetate, sodium propionate and sodium butyrate solutions above 0.015 mol kg -1 of salt concentration has not been observed in NaSa solution. The effect of salicylate ion on the critical micelle concentration of SDS and AOT and on the counter ion binding constant of AOT is attributed to mixed micelle formation of salicylate with the anionic surfactants. It is considered that the salicylate ions reside just outside the Stern layer of the anionic micelles and form ion - pairs with the sodium ions bound to the micelles. Salicylate ion does not seem to have significant influence on the surface activity of SDS and AOT. Standard free energies of micellization and adsorption of SDS and AOT in the presence of NaSa were also evaluated.

Micellization of AOT in aqueous sodium chloride, sodium acetate, sodium propionate, and sodium butyrate media: A case of two different concentration regions of counterion binding

Critical micelle concentrations of AOT in water in the presence of sodium chloride, sodium acetate, sodium propionate, and sodium butyrate were determined at 25 °C by the surface tension method. The co-ions do not have any effect on the value of critical micelle concentration. The surface density of AOT at the air–water interface increases in the presence of added electrolyte and attains a maximum value of 2.5±0.1 mol m−2 at a particular electrolyte concentration which is different for sodium chloride and the other three electrolytes. From the Corrin–Harkins plot it has been found that for AOT micelles the counterion binding constant has values 0.40 and 0.82 below and above ∼0.015 mol kg−1 electrolyte concentration (c∗), respectively. Measurement of sodium ion activity from the EMF method has confirmed such a shift in the counterion binding constant of AOT at c∗. The higher value of the counterion binding constant for AOT has been reported for the first time. From fluorescence spectroscopy it has been found that the aggregation number of AOT is 22 in water and its average aggregation numbers in the presence of electrolytes are about 34 and 136 below and above c∗, respectively. The increase by a factor of 2 in the counterion binding constant is shown to be due to a change in the shape of the AOT micelles around c∗. The shape of AOT micelles in the electrolyte concentration range ⩽c∗ is inferred to be oblate spheroid and a change from this shape appears to occur above c∗. A sudden increase in the polarity of the micelle–solution interface is also observed above c∗.

DPC와 CDEAB의 혼합마이셀화에 미치는 n-부탄올의 효과

The critical micelle concentration (CMC) and the counterion binding constant ( B) in a mixed micellar state of the Dodecylpyridinium chloride (DPC) with the Cetyldimethylethylammonium bromide (CDEAB) at 25 o C in aqueous solutions of n-butanol were determined as a function of α 1 (the overall mole fraction of DPC) by the use of elec- tric conductivity method. Various thermodynamic parameters ( Xi, γi, Ci, ai M , β, and ∆ Hmix) were calculated by means of the equations derived from the nonideal mixed micellar model. The effect of n-butanol on the mixed micellization of the DPC/CDEAB mixtures has been also studied by analyzing the measured and calculated thermodynamic parameters (CMC, B, and ∆ G o m).

Electrical Conductance Behavior of Oil-in-Water Microemulsions Stabilized by Sodium Dodecyl Sulfate and 1-Butanol

The specific conductivity of several oil-in-water (o/w) microemulsions (MEs) stabilized by sodium dodecyl sulfate and 1-butanol was measured at 25 °C as functions of the volume fraction of oil (φ0) and the molar ratio of water to surfactant (R). The oils used are octane, benzene, toluene, carbon tetrachloride, chloroform, cyclohexane, xylene, and nitrobenzene. The conductivity data were explained by the modified Bruggeman equation in the entire experimental range of φ0 in the case of octane and nitrobenzene and in a limited range of φ0 in the case of other oils. The value of the slope of this equation, f, is found to depend on (i) the concentration of surfactant or the R value, (ii) the nature of the oil, and (iii) the nature and number of substituents, if the oil is a substituted benzene. The specific conductivity data of o/w MEs of R = 120 and 100 were also analyzed in the light of the mixed electrolyte model, and the values of aggregation number, counterion binding constant, and radius of droplet were computed.

Estimation of micellization parameters of sodium dodecyl sulfate in water+1-butanol using the mixed electrolyte model for molar conductance

The mixed electrolyte model of Shanks and Franses has been applied to estimate the critical micelle concentration, aggregation number, and counterion binding constant of sodium dodecyl sulfate in a water + 1-butanol medium from its measured conductivity data at 25 °C. The surface potential of the ionic micelle in this mixed solvent medium was computed by solving the nonlinear Poisson–Boltzmann equation. The standard free energy terms of micellization were also calculated. The present study confirms further the observation made in the previous studies that ionic micelles do not contribute to the ionic strength of a surfactant solution, an inference originally made by McBain and coworkers.

Sodium n-Octanoate(SOC)와 n-Octylammonium Chloride(OAC)의 혼합마이셀화에 관한 연구

The critical micelle concentration(CMC) and the counterion binding constant(B) for the mixed micel-lization of sodium n-octanoate(SOC) with n-octylammonium chloride(OAC) were determined as a function of the overall mole fraction of Various thermodynamic parameters(, , , $$, and ) for the mixed micellization of the SOC/OAC systems have been calculated and analyzed by means of the equations derived from the nonideal mixed micellar model. The results show that there are great deviations from the ideal behavior for the mixed micellization of these systems. And other thermodynamic parameters(, , and ) associated with the micellization of SOC,OAC, and their have been also estimated from the temperature dependence of CMC and B values, and the significance of these parameters and their relation to the theory of the micelle formation have been considered and analyzed by comparing each other.

Micellization of Surfactants in Acetamide Melt

Electrical conductances of solutions of sodium dodecyl sulfate (SDS) and cetylpyridinium chloride (CPC) in acetamide melt were measured at 89 °C as a function of concentration. The dependence of molal conductance of SDS and CPC on concentration has been compared with that of normal electrolytes in acetamide melt. Both SDS and CPC are found to micellize in acetamide melt. A mixed electrolyte model has been used to compute the micellization parameters, viz., critical micelle concentration, aggregation number, and counterion binding constant, from the conductance data. Surface potentials of the micelles were computed by solving the nonlinearized Poisson−Boltzmann equation. The free energy terms for micellization were also evaluated.

Effect of Acetate and Propionate Co-ions on the Micellization of Sodium Dodecyl Sulfate in Water

Electrical conductivities of sodium dodecyl sulfate (SDS) in aqueous sodium acetate (NaAc) and sodium propionate (NaPr) solutions of different concentrations were measured at 25 °C. An anomalous behavior in the form of minima in the plots of critical micelle concentration (cmc) of SDS versus concentration of NaAc and NaPr was observed, thereby indicating the effect of acetate and propionate co-ions on micellization. The conductivity data were analyzed using a conductivity equation derived on the basis of a mixed-electrolyte model for surfactant solutions wherein ion−ion interactions were accounted for by the Debye−Hückel−Onsager equation. Such an analysis provided a method to estimate the values of cmc, counterion binding constant, and aggregation number directly from conductivity data. It was observed that ionic micelles contribute to electrical conductivity but not to ionic strength of surfactant solution. The surface potentials of SDS micelles in NaAc and NaPr solutions were computed by solving the Poisson−Boltzmann equation. The values of total free energy, electrostatic free energy, and hydrophobic free energy of micellization were estimated. The electrostatic free energy seems to control the decrease in cmc with added electrolyte concentration. On the other hand, the increase in cmc with NaAc and NaPr concentration appears to be due to the penetration of SDS micelles by the acetate and propionate co-ions.

Physico-chemical characterization of a double long-chain cationic amphiphile (Vectamidine) by microelectrophoresis

We recently synthesized a novel cationic amphiphile ( N- t-butyl- N′-tetradecyl-3-tetradecylaminopropionamidine or Vectamidine (previously described as diC 14-amidine)) that associates with DNA and RNA and facilitates their entry and expression into eukaryotic cells. Among several parameters that have been shown to influence the transfection process, the surface charge density plays a key role. Quantitative information about that charge density associated to the cationic amphiphiles organized in liposomal structure is not yet available. We provide here evidence by titration and microelectrophoresis measurements that an evaluation of the intrinsic acidity constants, the surface pH and the counterion binding constants allows to determine the charge density at physiological pH of Vectamidine liposomes. The knowledge of this superficial charge is a prerequisite to a molecular understanding of the DNA-cationic amphiphile complex formation. The method described could be extended to any kind of cationic amphiphile.