科研之友
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摘要
The interaction of a-cyclodextrin(alpha-CD) with ten ionic surfactants (S) in water was systematically examined using isothermal titration calorimetry. The S comprised cationic and anionic head groups while the hydrocarbon alkyl chain length varied from eight to fourteen carbon atoms. The heat data were measured at five temperatures ranging from 283.15 K to 318.15 K and were treated simultaneously allowing the estimation of a thermodynamically consistent temperature dependence of the equilibrium constant, as well as the enthalpy and heat capacity for the sequential formation of the [alpha-Cl/S] and the [alpha-CD2-S1 inclusion complexes. All attempts to fit the data assuming that only [alpha-CD"S] complexes are present failed. It was found that the thermodynamic footprint of the [alpha-CD.S] complexes does not depend importantly on the head group, while the formation and stabilization of the [alpha-CD2.S] complexes is strongly influenced by the chemical nature of the polar head group. Several contributions to the thermodynamic parameters are discussed in detail. Among the studied surfactants, the decyl- and octylsulfates were identified as those with a predominant content of [alpha-CD2.S] complexes and hence they are promising candidates to form viscoelastic films at the liquid/air interface, as it was found previously for the dodecylsulfate surfactant.
- 出版日期2017-11-1
