MICELLIZATION OF A POLYSTYRENE-BLOCK-POLY(ETHYLENE PROPYLENE) BLOCK-COPOLYMER IN KETONES

The concentration and temperature dependences on micelle formation by a polystyrene-block-poly(ethylene/propylene) copolymer in several keto nes (methyl ethyl ketone, methyl propyl ketone, diethyl ketone, methyl isobutyl ketone, dipropyl ketone, 5-methyl-2-hexanone and 5-methyl-3- heptanone) are studied by laser light scattering and viscometry. No mi celles were detected in solutions of 5-methyl-3-heptanone. The standar d Gibbs energy, DELTAG-degrees, the standard enthalpy, DELTAH-degrees, and the standard entropy, DELTAS-degrees, of micellization were estim ated from the dependence of the critical micelle temperature on concen tration. The values of DELTAG-degrees, DELTAH-degrees and DELTAS-degre es were negative for all ketones studied. DELTAG-degrees and DELTAH-de grees depend on the polar character of the ketone. The weight average molar mass, second virial coefficient and apparent radius of gyration have been calculated from the standard Zimm plots obtained. Huggins an d Kraemer equations have been employed to determine the limiting visco sity number of the micelles. The micelles formed in ketone solutions s how larger association numbers and densities than those formed in n-al kane solutions.