EFFECT OF WATER-SOLUBLE POLYMERS ON RODLIKE AND SPHERICAL MICELLES FORMED FROM 2-ALKYLMALONATE SALTS

The aggregation behavior of mono- and bis(tetramethylammonium) salts of 2-alkylmalonic acids (1-8) has been studied in aqueous solutions in the absence and presence of 0.5% (w/v) of poly(ethylene oxide) (PEO) or poly(vinyl methyl ether) (PVME). The mono-NMe4 salt of 2-dodecylmalonic acid forms rodlike micelles in a specific concentration range as evidenced by visually observed viscoelasticity of the solution and by H-1 NMR line broadening. The viscoelastic properties disappear upon addition of PEO or PVME, indicating a transition from rodlike to spherical, polymer-bound micelles. Interestingly, the interaction between the spherical micelles and the polymers is not accompanied by a reduction of the critical micelle concentration (cmc). The di-NMe4 salt of 2-dodecylmalonic acid forms spherical rather than rodlike micelles. The spherical micelles bind to PEO and PVME, and this interaction does lead to a considerable reduction of the cmc. Polymer-micelle interaction is also revealed by an increase of the clouding temperature for PVME. The experimental results are discussed in terms of interheadgroup interactions and recent theories for polymer-micelle association.