1H Nuclear magnetic relaxation study of the phase structure of polystyrene-block-poly(ethylene/propylene) copolymer micelles

Abstract

¹ H NMR longitudinal and transverse relaxation measurements have been made as a function of temperature for micellar solutions of a polystyrene-block-poly(ethylene/propylene) copolymer in [²H₁]octane. Spin diffusion following selective inversion of protons from one component has been used to probe the extent of mixing of the blocks in the interface between the micelle core consisting of slightly swollen polystyrene and the micelle fringe consisting of highly solvated poly(ethylene/propylene). At 80 °C a small degree of spin diffusion was detected, indicating that a mixed phase existed. A simple analysis of the magnitude of the effect showed that ca. 50% of the polystyrene lay in the boundary compared with only 3% of the poly(ethylene/propylene).