EFFECT OF INORGANIC SALTS ON THE MICELLAR BEHAVIOR OF ETHYLENE OXIDE-PROPYLENE OXIDE BLOCK-COPOLYMERS IN AQUEOUS-SOLUTION

The aggregation behaviour of two ethylene oxide-propylene oxide block copolymers (PEO-PPO-PEO) in aqueous solution has been investigated in the presence of added salts (KCNS, KI, KBr, KCl and KF) by viscosity, cloud point, light scattering, pulse gradient spin echo NMR, and solub ilization measurements. The salts have a strong effect on the cloud po ints of the pluronics. Both P-85 and L-64 form micelles which increase in size and change into elongated shapes when the cloud point is appr oached. The changes of size and shape of the micelles, revealed by the intrinsic viscosity and rheological properties, seem to occur at the same temperature relative to the cloud point, independent of the natur e of the salt. The onset of micelle formation is also shifted in the s ame direction as the cloud point by the salts, but by a much smaller a mount.