terms of the increasing hydrophobicity of PEO with temperature.
numbers lower than those of free SDS micelles in water
In terms of bound charges per polymer repeat unit, the interaction and increase with the surfactant concentration at constant of Cd 2/ and Mg 2/ ions with PEO or PVP is stronger than that of polymer concentration (6, 7). Further increases in SDS con-Na / ions with the same polymers. The interaction strength thus centration result in saturation of the polymer and in formafollows the same sequence as the counterion degree of binding to free micelles. However, the values of the free energy of transfer of tion of free SDS micelles when the concentration of free a dodecylsulfate ion from a free micelle to a polymer-bound aggredodecyl sulfate ions reaches the cmc of SDS in the absence gate are not very different with Na / and divalent metal counterof polymer. Several explanations have been proposed for ions, and are extremely small. The results obtained with the salt/ the interaction between neutral polymers and anionic surfacpolymer systems confirm the binding of cations by PEO and PVP tants. For the PEO-SDS system, the proposed explanations in aqueous solutions. แญง 1997 Academic Press involve hydrophobic contacts between PEO and surfactant Key Words: interactions; magnesium dodecyl sulfate/polyoxyhydrophobic groups on the aggregate surface (8, 9), a partial ethylene; cadmium dodecyl sulfate/polyoxyethylene; electrical protonation giving a positive charge to some polymer ether conductance polymer/surfactant systems; fluorescence probing groups (10), and a specific interaction between ionic head polymer/surfactant systems; aggregation numbers in polymer/surgroups and polymer ether groups (11). Recent studies sugfactant systems.
gest that the interaction between bound aggregates and polymers is mediated by polymer-bound surfactant counterions (12)(13)(14)(15)(16). Whatever the mechanism of interaction, it is gen-1 To whom correspondence should be addressed.
erally agreed that polymer-surfactant complexes can be de-130