Largely Tunable Morphologies Self-Assembled by A(AB)n Miktoarm Star Copolymer in Solutions

Precise control of self-assembled structures in solution by tailoring molecular architecture is of great significance for the utilization of amphiphilic block copolymers. Inspired by the topological design principle via regulating the effect of spontaneous curvature in bulk, here, we focus on the self-assembly behavior of A '(A '' B)n miktoarm star copolymer in dilute solution with tunable molecular architecture and spontaneous curvature through changing architectural parameters, including the volume fraction of A-blocks (f), the ratio of volume fraction of A '-block to the total A-blocks (tau), and the arm number (n). We use dissipative particle dynamics to investigate the phase behavior and self-assembled morphologies of A '(A '' B)n copolymer in terms of tau and fin the B-selective and A-selective solvents, which exhibit notable differences due to the opposite effect of molecular spontaneous curvature. The stability region of morphologies with low interfacial curvature, such as vesicular structures, is relatively small in the B-selective solvent while that is expanded remarkably in the A-selective solvent. Compared with the monotonic shift of phase boundary between micellar structures and vesicular structures with tau in the B-selective solvent, the phase boundary shifts nonmonotonically in the A-selective solvent, with the appearance of more complex structures. It is noteworthy that the effect of bridge conformation of A ''-blocks also greatly affects the self-assembly behavior in solution, and the longer A ''-blocks promote the formation of vesicular structures and complex aggregates of assemblies. Moreover, the decrease of copolymer solubility caused by the effect of steric hindrance originating from molecular architecture has a tendency to drive the morphological transition from simple vesicles to compound vesicles in the A-selective solvent. Thus, by tuning the architecture of A '(A '' B)n in different solutions, the effects of three mechanisms involving molecular curvature, bridge conformation, and copolymer solubility can be synergistically regulated to obtain abundant and desired nanostructures. These results deepen the understanding of the molecular design of amphiphilic block copolymers and provide theoretical guidance for preparing required morphologies in experiments.