INTERACTIONS BETWEEN SURFACTANTS AND UNCHARGED POLYMERS IN AQUEOUS-SOLUTION STUDIED BY MICROCALORIMETRY

The interaction between ionic surfactants and uncharged polymers in dilute aqueous solution has been studied by titration microcalorimetry. The resulting enthalpic titration curves give detailed information about polymer - surfactant interactions. While sodium dodecylsulfate interacts strongly with poly(ethylene oxide) and poly(vinyl-pyrrolidone), the micelle formation of the cationic surfactants dodecyl-, tetradecyl-, and hexadecyl-trimethylammonium bromide is not measurably perturbed by the presence of these polymers. However, there is no significant difference the interaction of the anionic and cationic surfactants with ethyl(hydroxyethyl)cellulose ethers. The aggregation of surfactants in polymer solutions shows clear similarities to the solubilization of small, polar molecules in ionic micelles. Preaggregation between surfactant monomers and polymers can be significant as indicated by sizeable endothermic enthalpy contributions from hydrophobic pair-wise interaction.