Thermodynamics of micelle formation of the ephedrine-based chiral cationic surfactant DMEB in water, and the intercalation of DMEB in montmorillonite

Annamária B. Páhi, Dénes Varga, Z. Király, A. Mastalir

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9 Citations (Scopus)

Abstract

The solubility and the micelle formation of the chiral cationic surfactant (1R,2S)-(-)-N-dodecyl-N-methylephedrinium bromide (DMEB) in aqueous solution were investigated by conductometry and titration microcalorimetry in the temperature range of 278-328 K. The Krafft temperature of DMEB is TK = 280 K and the solubility of the surfactant at this point is 4.5 mM. The cmc versus T curve passes through a shallow minimum close to room temperature. The micelle formation changes from endothermic to exothermic at this characteristic temperature. The apparent degree of dissociation of the micelles αapp increases slightly as the temperature is raised. The isosteric enthalpies of micelle formation, ΔHst mic, are close to the calorimetrically measured enthalpies, ΔHmic, provided that the real degree of dissociation, αst = 1, is used in the calculations. ΔHmic and the temperature dependence of ΔHmic of DMEB are markedly similar to those of sodium dodecylsulfate and dodecyltrimethylammonium bromide. The micelle formation of DMEB is favored by both enthalpy and entropy at and above room temperature. The enthalpy-entropy compensation results in a slight decrease in the Gibbs free energy on increase of the temperature. Sodium montmorillonite (M) was rendered organophilic by DMEB via ion-exchange to produce the clay/organocomplex DME-M. The swelling properties of the organoclay were investigated by XRD measurements in a variety of organic solvents. The basal spacing of DME-M varied from 1.8 to 3.5 nm, depending on the nature of the solvent. DME-M is a heterogenized ephedrine derivative, which may be regarded as a potential catalyst for enantioselective organic syntheses.

Original languageEnglish
Pages (from-to)77-83
Number of pages7
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Volume319
Issue number1-3
DOIs
Publication statusPublished - Apr 15 2008

Fingerprint

Bentonite
Ephedrine
Cationic surfactants
Micelles
montmorillonite
Intercalation
Clay minerals
Bromides
intercalation
bromides
micelles
surfactants
Thermodynamics
thermodynamics
Water
enthalpy
water
Enthalpy
Temperature
solubility

Keywords

  • Chiral surfactant
  • Conductometry
  • Micelle
  • Microcalorimetry
  • Montmorillonite

ASJC Scopus subject areas

  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry

Cite this

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title = "Thermodynamics of micelle formation of the ephedrine-based chiral cationic surfactant DMEB in water, and the intercalation of DMEB in montmorillonite",
abstract = "The solubility and the micelle formation of the chiral cationic surfactant (1R,2S)-(-)-N-dodecyl-N-methylephedrinium bromide (DMEB) in aqueous solution were investigated by conductometry and titration microcalorimetry in the temperature range of 278-328 K. The Krafft temperature of DMEB is TK = 280 K and the solubility of the surfactant at this point is 4.5 mM. The cmc versus T curve passes through a shallow minimum close to room temperature. The micelle formation changes from endothermic to exothermic at this characteristic temperature. The apparent degree of dissociation of the micelles αapp increases slightly as the temperature is raised. The isosteric enthalpies of micelle formation, ΔHst mic, are close to the calorimetrically measured enthalpies, ΔHmic, provided that the real degree of dissociation, αst = 1, is used in the calculations. ΔHmic and the temperature dependence of ΔHmic of DMEB are markedly similar to those of sodium dodecylsulfate and dodecyltrimethylammonium bromide. The micelle formation of DMEB is favored by both enthalpy and entropy at and above room temperature. The enthalpy-entropy compensation results in a slight decrease in the Gibbs free energy on increase of the temperature. Sodium montmorillonite (M) was rendered organophilic by DMEB via ion-exchange to produce the clay/organocomplex DME-M. The swelling properties of the organoclay were investigated by XRD measurements in a variety of organic solvents. The basal spacing of DME-M varied from 1.8 to 3.5 nm, depending on the nature of the solvent. DME-M is a heterogenized ephedrine derivative, which may be regarded as a potential catalyst for enantioselective organic syntheses.",
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T1 - Thermodynamics of micelle formation of the ephedrine-based chiral cationic surfactant DMEB in water, and the intercalation of DMEB in montmorillonite

AU - Páhi, Annamária B.

AU - Varga, Dénes

AU - Király, Z.

AU - Mastalir, A.

PY - 2008/4/15

Y1 - 2008/4/15

N2 - The solubility and the micelle formation of the chiral cationic surfactant (1R,2S)-(-)-N-dodecyl-N-methylephedrinium bromide (DMEB) in aqueous solution were investigated by conductometry and titration microcalorimetry in the temperature range of 278-328 K. The Krafft temperature of DMEB is TK = 280 K and the solubility of the surfactant at this point is 4.5 mM. The cmc versus T curve passes through a shallow minimum close to room temperature. The micelle formation changes from endothermic to exothermic at this characteristic temperature. The apparent degree of dissociation of the micelles αapp increases slightly as the temperature is raised. The isosteric enthalpies of micelle formation, ΔHst mic, are close to the calorimetrically measured enthalpies, ΔHmic, provided that the real degree of dissociation, αst = 1, is used in the calculations. ΔHmic and the temperature dependence of ΔHmic of DMEB are markedly similar to those of sodium dodecylsulfate and dodecyltrimethylammonium bromide. The micelle formation of DMEB is favored by both enthalpy and entropy at and above room temperature. The enthalpy-entropy compensation results in a slight decrease in the Gibbs free energy on increase of the temperature. Sodium montmorillonite (M) was rendered organophilic by DMEB via ion-exchange to produce the clay/organocomplex DME-M. The swelling properties of the organoclay were investigated by XRD measurements in a variety of organic solvents. The basal spacing of DME-M varied from 1.8 to 3.5 nm, depending on the nature of the solvent. DME-M is a heterogenized ephedrine derivative, which may be regarded as a potential catalyst for enantioselective organic syntheses.

AB - The solubility and the micelle formation of the chiral cationic surfactant (1R,2S)-(-)-N-dodecyl-N-methylephedrinium bromide (DMEB) in aqueous solution were investigated by conductometry and titration microcalorimetry in the temperature range of 278-328 K. The Krafft temperature of DMEB is TK = 280 K and the solubility of the surfactant at this point is 4.5 mM. The cmc versus T curve passes through a shallow minimum close to room temperature. The micelle formation changes from endothermic to exothermic at this characteristic temperature. The apparent degree of dissociation of the micelles αapp increases slightly as the temperature is raised. The isosteric enthalpies of micelle formation, ΔHst mic, are close to the calorimetrically measured enthalpies, ΔHmic, provided that the real degree of dissociation, αst = 1, is used in the calculations. ΔHmic and the temperature dependence of ΔHmic of DMEB are markedly similar to those of sodium dodecylsulfate and dodecyltrimethylammonium bromide. The micelle formation of DMEB is favored by both enthalpy and entropy at and above room temperature. The enthalpy-entropy compensation results in a slight decrease in the Gibbs free energy on increase of the temperature. Sodium montmorillonite (M) was rendered organophilic by DMEB via ion-exchange to produce the clay/organocomplex DME-M. The swelling properties of the organoclay were investigated by XRD measurements in a variety of organic solvents. The basal spacing of DME-M varied from 1.8 to 3.5 nm, depending on the nature of the solvent. DME-M is a heterogenized ephedrine derivative, which may be regarded as a potential catalyst for enantioselective organic syntheses.

KW - Chiral surfactant

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KW - Micelle

KW - Microcalorimetry

KW - Montmorillonite

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