Interactions between gemini surfactants, 12-s-12, and beta-cyclodextrin as investigated by NMR diffusometry and electric conductometry

Markus Nilsson, Celia Cabaleiro-Lago, Artur J. M. Valente, Olle Soderman

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54 Citations (Scopus)

Abstract

The interaction between beta-cyclodextrin (CD) and gemini surfactant of the type alkyl-alpha,omega-bis(dodecyldimethyl-ammonium bromide) with different spacer lengths of 2, 8, and 10 carbons has been investigated by means of electric conductivity (EC) and proton self-diffusion NMR at 298 K. The formation of a 2: 1 (CD: gemini) complex in a two-step mechanism is observed with the first association constant (K-11) higher than the second one (K-21), but both relatively small in comparison with single C-12-tailed surfactant. The value of the association constants increased with spacer length both for the first and second associated CD, which indicates that the available space on the gemini molecule is important. The magnitudes of the association constant both for the first and second complexation are discussed. The first association constant is small ( when compared with the homologous single-chain surfactant) due to hydrophobic interaction between the hydrocarbon tails within the gemini molecule, while the second association constant shows no cooperativity and its magnitude is discussed in terms of steric constrains.

Original languageEnglish
Pages (from-to)8663-8669
Number of pages6
JournalLangmuir
Volume22
Issue number21
DOIs
Publication statusPublished - 2006
Externally publishedYes

Swedish Standard Keywords

  • Physical Chemistry (10402)

Keywords

  • Association reactions
  • N-octyl
  • alpha-cyclodextrin
  • aqueous-solutions
  • association constants
  • complexation
  • electric conductivity
  • gemini molecules
  • hydrocarbons
  • nuclear magnetic resonance
  • self-diffusion NMR
  • spacer lengths
  • steric constrains
  • surface active agents
  • systems

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