Dilute and semidilute solutions of ABA block copolymer in solvents selective for A or B blocks: 2. Light scattering and sedimentation study

Abstract

Micellar solutions of a triblock copolymer polystyrene- block-poly(hydrogenated butadiene)- block-polystyrene, in heptane and in 1,4- dioxane 25 vol% heptane have been studied by light scattering and sedimentation velocity methods. In dilute solutions, micellar molar mass, hydrodynamic radius of micelles, average volume fraction of polymer segments in a micellar core and in the whole micelle, and the unimer/micelles ratio have been determined. While in semidilute mixed solvent solutions only one diffusion mode, corresponding to collective diffusion, has been determined, at least two modes, diffusion and relaxation ones, have been observed in spectra of decay times in semidilute heptane solutions. Micellar models have been proposed for both systems under study, accommodating satisfactorily all experimental results.