A VOLUMETRIC STUDY OF BETA-CYCLODEXTRIN HYDROCARBON AND BETA-CYCLODEXTRIN/FLUOROCARBON SURFACTANT INCLUSION COMPLEXES IN AQUEOUS-SOLUTIONS/

The apparent molar volumes (V-phi,V-S) of a homologous series of hydro carbon (hc) (CxH2+1CO2Na, x = 2, 5-9, 11, 13) and perfluorocarbon (fc) (CxF2x+1CO2Na, x = 1, 3, 4, 6-9) surfactants (S) have been determined in water and in binary solvent (H2O + beta-cyclodextrin (beta-CD)) sy stems at 25 degrees C. The apparent molar volumes of beta-CD (V-phi,V- CD) in water and in binary (H2O + S) systems containing he and fc surf actants have also been obtained. The results show that the magnitudes of V-phi,V-S and V-phi,V-CD are greater in ternary solutions than in t he binary aqueous systems. The apparent molar volumes at infinite dilu tion (V(phi)degrees) of beta-CD and of the surfactants in ternary solu tions are observed to depend on the following factors: (i) the magnitu de of the binding constant (K-i), (ii) the alkyl chain length of the s urfactant, (iii) the mole ratio of the host to guest species, (iv) the host/guest stoichiometry, and (v) the physicochemical properties of t he surfactant. The volumetric properties of the ternary systems have b een analyzed in terms of the complexed and uncomplexed species by appl ication of Young's rule. The formation of beta-CD/surfactant complexes having 1:1 and 1:1 plus 2:1 stoichiometries were successfully modeled using two-site and three-site models, respectively.