(105f) Dynamics of AnBn Miktoarm Star Copolymers

Understanding self-organization and structure of complex macromolecular architectures is of interest because of the conformational differences caused by geometric constraints. In an effort to a better understand of the effects of polymer architecture and the dynamic behavior and structure of branched copolymers, we have anionically synthesized four polystyrene (PS)/polyisoprene (PI) symmetric miktoarm stars having AnBn arrangements with 2, 4, 8 and 16 arms, as shown in the Figure. By systematically doubling the number of arms, and consequently the molecular weight, we can elucidate the effects of increasing the intramolecular interactions on self-assembly and dynamics in solution. The materials were characterized by SEC-LS and 1H NMR in order to determine the molecular weight and the branched conformation. Dynamic light scattering experiments in n-hexane, a selective solvent for PI, showed monomodal hydrodynamic size, Rh, distributions for the two largest samples (A4B4 and A8B8). The diblock copolymer, sample A1B1, presented two distinct Rh at concentrations equal to and greater than 0.75 mg/mL. This is an indication of the coexistence of single chains in solution with micellar aggregates. Similarly, sample A2B2 showed diffusive behavior of two populations at high concentrations. Detailed results of the dynamic behavior of these miktoarm stars in n-hexane will be presented. Technological areas such as drug delivery and nanoparticle formation can benefit from these fundamental studies.