Small-angle neutron scattering study of onion-type micelles

Full Paper: Onion-type block copolymer micelles were prepared from polystyrene-block-poly(2-vinylpyridine) (PS-b-PVP) inner micelles in an acidic solution by basifying in the presence of poly(2-vinylpyridine)-block-poly(ethylene oxide) (PVP-b-PEO). This has the effect of depositing the PVP-b-PEO onto the collapsed corona of the PS-b-PVP micelle. These core PS-b-PVP micelles, the small micelles formed by PVP-b-PEO, and the resulting onion micelles were studied by small angle neutron scattering (SANS) techniques. Two recently developed evaluation techniques were employed: 1. Bare-core approximation, which utilizes the data at larger scattering angles and provided information about the size and polydispersity of the micelle cores. 2. Application of the Pedersen and Gerstenberg micelle model, which utilizes the whole scattering curve. Due to their polyelectrolyte nature, the core micelles had very extended coronas corresponding to rather large statistical segment lengths. The SANS data at large scattering angles for the solution of onion-type micelles revealed the presence of a significant number of the small PVP-b-PEO micelles.: The contribution of the small micelles to the total scattering was subtracted and the properties and polydispersities of onion cores and stabilizing PEO coronas were obtained. [GRAPHICS]