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Micellar properties of surface active ionic liquids: A comparison of 1-hexadecyl-3-methylimidazolium chloride with structurally related cationic surfactants

Galgano, Paula D.; Seoud, Omar A. El Universidade De São Paulo

JOURNAL OF COLLOID AND INTERFACE SCIENCE, v.345, n.1, p.1-11, 2010

ACADEMIC PRESS INC ELSEVIER SCIENCE 2010

Acesso online

  • Título:
    Micellar properties of surface active ionic liquids: A comparison of 1-hexadecyl-3-methylimidazolium chloride with structurally related cationic surfactants
  • Autor: Galgano, Paula D.; Seoud, Omar A. El
  • Universidade De São Paulo
  • Assuntos: Surface Active Ionic Liquids; Conductivity Of Cationic Micelles; Isothermal Titration Calorimetry Of Cationic Micelles; Light Scattering; Polarity Of Interfacial Water; 1-Hexadecyl-3-Methylimidazolium Chloride; 1-Hexadecylpyridinium Chloride; Benzyl(3-Hexadecanoylaminoethyl)Dimethylammonium Chloride; Sodium Dodecyl-Sulfate; Enthalpy-Entropy Compensation; Cetyl Pyridinium Chloride; Aqueous-Solutions; Temperature-Dependence; Aggregation Behavior; Vant-Hoff; Significant Discrepancies; Cetylpyridinium Chloride; Thermodynamic Properties; Chemistry; Physical
  • É parte de: JOURNAL OF COLLOID AND INTERFACE SCIENCE, v.345, n.1, p.1-11, 2010
  • Descrição: Ionic liquids, ILs, carrying long-chain alkyl groups are surface active, SAIIs. We investigated the micellar properties of the SAIL 1-hexadecyl-3-methylimidazolium chloride, C(16)MeImCl, and compared the data with 1-hexadecylpyridinium chloride, C(16)PYCl, and benzyl (3-hexadecanoylaminoethyl)dimethylammonium chloride, C(15)AEtBzMe(2)Cl. The properties compared include critical micelle concentration, cmc; thermodynamic parameters of micellization; empirical polarity and water concentrations in the interfacial regions. In the temperature range from 15 to 75 degrees C, the order of cmc in H(2)O and in D(2)O is C(16)PYCl > C(16)MeImCl > C(15)AEtBzMe(2)Cl. The enthalpies of micellization, Delta H(mic)(degrees), were calculated indirectly from by use of the van`t Hoff treatment; directly by isothermal titration calorimetry, ITC. Calculation of the degree of counter-ion dissociation, alpha(mic), from conductivity measurements, by use of Evans equation requires knowledge of the aggregation numbers, N(agg), at different temperatures. We have introduced a reliable method for carrying out this calculation, based on the volume and length of the monomer, and the dependence of N(agg) on temperature. The N(agg) calculated for C(16)PyCl and C(16)MeImCl were corroborated by light scattering measurements. Conductivity- and ITC-based Delta H(mic)(degrees) do not agree; reasons for this discrepancy are discussed. Micelle formation is entropy driven: at all studied temperatures for C(16)MeImCl; only up to 65 degrees C for C(16)PyCl; and up to 55 degrees C for C(15)AEtBzMe(2)Cl. All these data can be rationalized by considering hydrogen-bonding between the head-ions of the monomers in the micellar aggregate. The empirical polarities and concentrations of interfacial water were found to be independent of the nature of the head-group. (C) 2010 Elsevier Inc. All rights reserved.
    FAPESP (State of Sao Paulo Research Foundation)
    CNPq (National Council for Scientific and Technological Research)
  • DOI: 10.1016/j.jcis.2010.01.078
  • Títulos relacionados: Journal of Colloid and Interface Science
  • Editor: ACADEMIC PRESS INC ELSEVIER SCIENCE
  • Data de publicação: 2010
  • Idioma: Inglês

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