EFFECT OF POTASSIUM FLUORIDE ON THE MICELLAR BEHAVIOR OF PLURONIC F-68 IN AQUEOUS-SOLUTION

The cloud point of Pluronic F68, a triblock copolymer of the type PEO/PPO/PEO with average composition EO78PO30EO78, is reduced by 50-degrees-C when 1.0 M KF is added to the aqueous solution. The aggregation properties are also affected. The size of the unimers and micelles in the solution, as estimated from diffusion coefficients, determined by dynamic light scattering and NMR self-diffusion measurements, or molecular weights from static light scattering, are similar with and without salt present, but the growth of the micelles starts at a lower temperature-25-degrees-C in 1.0 M KF, 44-degrees-C in water, values from extrapolation to zero concentration-and continues over a wider temperature range in the salt solution. The intrinsic viscosity indicates that the micelles are less compact-more solvated-than those formed by the more hydrophobic members of the Pluronics family but become less solvated with increasing temperature than PEO fractions of similar molecular weight.