Structure of polystyrene‐<i>block</i>‐poly(ethylene oxide) diblock copolymer micelles in water

Abstract

Abstract Micellization in water of two homologous series of AB‐type diblock copolymers, composed of polystyrene (PS) as the A block and poly(ethylene oxide) (PEO) as the B block, were investigated by small‐angle X‐ray scattering (SAXS) and dynamic light scattering (DLS). The copolymers have molecular weights M n in the range 2 000—34 800, and have in a given series, the same number of repeating units of the PS block, ( N PS = 10 and 38), and a variable number of repeating units of the PEO block ( N PEO values in the range 23–704). In order to avoid secondary association of micelles, a dialysis technique was used to prepare the micellar systems, in the case of copolymers having high M n values of the PS block. The experimental micelle properties such as the core radius R c and the aggregation number N of non‐equilibrium structures, so called “frozen micelles”, obtained by dialysis, were found to be independent of the copolymer characteristics. However, for equilibrium structures, obtained by direct solubilization of the copolymers ( N PS = 10) in water, R c and N were found to decrease with increasing N PEO for the homologous series.