SANS STUDY OF THE MICELLAR STRUCTURE OF PEO PPO/PEO AQUEOUS-SOLUTION/

Small-angle neutron scattering (SANS) was used to investigate the mice llar structure formed by a poly(oxyethylene-oxypropylene-oxyethylene) (PEO(13)PPO(30)PEO(13), Pluronic L64) copolymer in D2O over a temperat ure range of 8.4-35.0 degrees C. The intermicellar interactions were c orrected by using an equivalent hard sphere approximation with an equi valent hard sphere radius. The aggregation number of the micelles decr eased with decreasing temperature. The micellar scattering behavior co uld be well described by a core-shell structure. Based on the core-she ll model, the volume fraction of the polymer segments in the micellar shell. was less than 0.2. The micellar molar mass became larger after having introduced an organic solvent (xylene) into the system and incr eased with increasing amount of solubilized xylene. The maximum amount of solubilized xylene in the micelle was of the order of 0.3-0.4 xyle ne molecule per PO unit.