Influence of the block length on the structure of micelles formed by polystyrene-block-poly(ethylene-co-propene) in octane and 5-methyl-2-hexanone

The influence of molar mass and chemical composition of the copolymer on the structural parameters of copolymer micelles was investigated. Two polystyrene-block-poly(ethylene-co-propene) copolymers with the same polystyrene block length but different poly(ethylene-co-propene) length were used. The micelles were studied in solutions of octane and 5-methyl-2-hexanone, selective solvents for poly(ethylene-co-propene) (PEP) and polystyrene (PS) blocks, respectively. Static light scattering and viscosity measurements were carried out in order to determine the weight-average molar mass, radius of gyration, second virial coefficient and hydrodynamic radius of the micelles. The association number of the micelles depends on the location of the largest copolymer block in the micelle structure. An influence of the copolymer structure on the micelle dimensions was also found.