Micellization of model graft copolymers in dilute solution

The micellization behaviors of graft copolymers consisting of polystyrene, PSt, backbones and poly(tert-butyl methacrylate), PtBuMA, or poly(methacrylic acid), PMAA, branches were studied in dilute solutions by low angle laser light scattering, LALLS, viscometry, and dynamic light scattering, DLS. tert-Amyl alcohol, a selective solvent for the PtBuMA branches, and tetrahydrofuran, THF, a selective solvent for the PSt backbones, were used to promote the formation of micelles from the PSt-g-PtBuMA and PSt-g-PMAA graft copolymers, respectively. Low aggregation numbers were obtained in all cases due to the specific architectural characteristics of the samples. Aggregation numbers were dependent on the type of the component (backbone or branches) that was insoluble in the selective solvent. The formation of micelles from the PSt-g-PtBuMA graft copolymers in tert-amyl alcohol is evidenced by the appearance of large and rather loose aggregates at a certain concentration range. This kind of behavior was not observed for the micelles formed from the graft copolymers with PMAA branches in THF. Stable and compact structures were obtained in this case, with their hydrodynamic behavior resembling that of hard spheres.