6533b86cfe1ef96bd12c7ff4

RESEARCH PRODUCT

Thermodynamic Evidence of Cyclodextrin−Micelle Interactions

subject

description

The enthalpy of transfer (ΔHt) of hydroxypropyl-α-cyclodextrin (HP-α-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD), and β-cyclodextrin (β-CD) from water to the aqueous C6F13CO2Na and C7F15CO2Na solutions were determined in the pre- and post-micellar regions. The behavior of the macrocycles is system specific. Generally, the magnitude of the enthalpy is influenced by several factors:  (1) the alkyl chain length of the surfactant, (2) the cyclodextrin cavity and its alkylation, (3) the interactions between the free cyclodextrin and the free surfactant, (4) the host−guest equilibrium constant, (5) the host/guest stoichiometry, and (6) the micelle-cyclodextrin (free and/or complexed) interactions. As far as the premicellar region is concerned, HP-α-CD does not form the host−guest complexes. β-CD and HP-β-CD in the aqueous C7F15CO2Na solutions form host−guest complexes of 1:1 stoichiometry; β-CD shows a larger binding affinity toward the surfactant as a compensative effect between the more negative enthalpy and ...