Morphologies and phase diagrams of ABC star triblock copolymers confined in a spherical cavity

The morphologies and phase diagrams exhibited by symmetric ABC star triblock copolymer nanoparticles are investigated by using the real-space self-consistent field theory. A variety of three-dimensional morphologies, such as spherically concentric lamellae and ring-like structures, are identified in the triangular phase diagrams for the polymeric nanoparticles, depending on the volume fractions of the components and the interaction between the polymers and the confining spherical surface. We first study a number of examples where the confining radius and degree of interactions between the polymer and the spherical surface are fixed. A neutral surface that has no energetic preference on any ABC component induces ring-like structures in axisymmetry in an orbicular region of the phase diagram, which surrounds the central region where distorted cylinder phases are stable; a spherical surface that attracts one of the three polymer components induces distorted cylinders into the ring-like structures in a central region of the phase diagram; a spherical surface that repels one of the components stabilizes a lamella-like structure in spherical symmetry in a large region of the phase diagrams. We then focus on an example of polygonal tiling morphologies to study the effects due to variations of the spherical radius and the degree of interactions between the polymer and the spherical surface. The results show that the degree of interactions can obviously influence the formation of morphologies but the spherical radius only affects the polygonal tiling morphologies through slightly adjusting their natural arrangement in the neutral surface case. The ring-like structures of ABC star triblock copolymer nanoparticles are distributed in an orbicular region of the phase diagram.