Structure of (deuterated PEO) (PPO) (deuterated PEO) block copolymer micelles as determined by small angle neutron scattering

The structure of(deuterated ethylene oxide)(23)-(propylene oxide)(34)-(deut erated ethylene oxide)(34) block copolymer micelles was studied in the unim er-to-micelle transition region using small angle neutron scattering (SANS) . A three-parameter core-corona model fit to the set of scattering curves o btained with various mixtures of D2O and H2O as the solvent yielded the agg regation number, the core and corona radii, and the water contents of the c ore and the corona. The results showed that the micellar core cannot consis t of PPO only but must contain significant quantities of water. The micelle aggregation number increased with temperature while the core and corona ra dii were constant over a 10 degrees C temperature region above the critical micellization temperature. The values of the corona radius obtained from t he model fit (56-57 +/- 3 Angstrom) are in a good agreement with the hydrod ynamic radius of the micelle (56-61 +/- 2 Angstrom) measured by dynamic lig ht scattering.