AGGREGATION OF A POLY(ETHYLENE OXIDE) POLY(PROPYLENE OXIDE) POLY(ETHYLENE OXIDE) TRIBLOCK COPOLYMER IN AQUEOUS-SOLUTION STUDIED USING RAYLEIGH BRILLOUIN AND DYNAMIC LIGHT-SCATTERING

Aqueous solutions of a PEO-PPO-PEO copolymer were studied using Raylei gh-Brillouin (R-B) and dynamic light scattering (DLS) over the concent ration range 0.1-0.4 g/mL as a function of temperature. The purpose wa s to investigate associative and aggregation phenomena in the system. Although the R-B spectra were not influenced by the micellar to cubic phase transition, both the sound velocity (v) and spatial attenuation (alpha) increased with decreasing temperature below the phase transiti on temperature in the region in which micellar cluster formation is ob served using DLS. The observations can be explained in terms of the st ructure of the solutions. The increase in v and alpha is shown to be c aused by the scattering of sound waves by the clusters.