Equilibrium Self-Assembly, Structure, and Dynamics of Clusters of Star-Like Micelles

Hierarchical structure and dynamics of clusters of self-assembled star-like micelles formed by oligocarbonate-fluorene end-functionalized poly(ethylene glycol) triblock copolymers were characterized by small-angle neutron scattering and static and dynamic light scattering at concentrations below the gel point. These micelles persist in equilibrium with concentration-dependent sized hierarchical clusters. When probed at length scales within the clusters by dynamic light scattering, the clusters exhibit Zimm dynamics, reminiscent of dilute mesoscale chains. The ability to form chain-like clusters is attributed to the π-π stacking of the fluorene groups that drives the formation of micelles. This enables a design variable to control the rheology of injectable gels. Further, predictions of the solvent (D₂O) viscosity show deviations consistent with polymers in organic solvents, stressing a need for refinement of molecular theories of polymer dynamics.