Micellization behavior of model asymmetric miktoarm star copolymers of the AA′B type, where A is polyisoprene and B is polystyrene

Abstract

Model asymmetric miktoarm star copolymers of the type AA′B, where A and A′ are polyisoprenes (PIs) and B is deuterated polystyrene (PS), were synthesized by anionic polymerization high-vacuum techniques. Their micellization behavior was studied in n-decane, a selective solvent for the PI blocks, and N,N-dimethylacetamide (DMA), selective for the PS blocks. Utilizing static and dynamic light-scattering techniques along with dilute solution viscometry, parameters such as the aggregation number, Nw, the hydrodynamic and viscometric radii were determined. Based on these results, structural parameters of the micelles, that is, core and corona radii, as well as core-corona interfacial area, were calculated. The thermal stability of the micelles was also examined in both selective solvents. The macromolecular architecture was found to have a considerable effect on the micellization behavior of the block copolymers. Static light-scattering techniques were utilized to study the micellization behavior of model asymmetric miktoarm star copolymers of the type AA′B, where A and A′ are polyisoprenes (PIs) and B is deuterated polystyrene (PS). In n-decane, a selective solvent for the PI blocks the comparison between linear PS–PI diblocks, symmetric PS(PI)2 and asymmetric PS(PI)(PI′) miktoarm stars, and confirms that the aggregation numbers (Nw) and, in general, the micellar properties can be manipulated at will, and that tailor-made micelles can be constructed changing the macromolecular architecture.